Picture 1 – Cable ladder system
UPDATE March 15, 2011: This blog is now being re-constructed. Please read the re-opening post here, Blog Re-construction.
Copyright http://electricalinstallationblog.blogspot.com/ - Electrical cable ladder pictures
Showing posts with label Building electrical. Show all posts
Showing posts with label Building electrical. Show all posts
Wednesday, January 13, 2010
Electrical cable ladder pictures
Below is a picture of cable ladder installation. I only have time for this picture today, but you will be able to see more installation pictures of this component of electrical installations soon. However, you can see more pictures of electrical installations in my other posts on this blog by visiting this anchor post, Free electric installation pictures. You can also see cable tray pictures at this post, Cable trays and ladder installation.
Picture 1 – Cable ladder system
UPDATE March 15, 2011: This blog is now being re-constructed. Please read the re-opening post here, Blog Re-construction.
Copyright http://electricalinstallationblog.blogspot.com/ - Electrical cable ladder pictures
Picture 1 – Cable ladder system
UPDATE March 15, 2011: This blog is now being re-constructed. Please read the re-opening post here, Blog Re-construction.
Copyright http://electricalinstallationblog.blogspot.com/ - Electrical cable ladder pictures
Sunday, January 10, 2010
Emergency light installation pics
I have uploaded few pictures showing the method of installing a ceiling-recessed emergency lighting (EL) unit. This work was photographs at a high-rise building construction a few months ago.
As far as the choice of types of the EL light, I would personally prefer a surface mounted self-contained type. The one being installed in this picture is also a battery-backed self-contain type, but it is recessed mounted.
Being a technical guy, the surface mounted type of emergency lighting gives a certain feeling of comfort in my opinion. That is because you can see the whole unit right at the surface of the ceiling. As this lighting is intended for emergency (the failure of the mains supply can also be considered an form of emergency in my view because no high-rise building can operate without the mains supply. So, the standby electrical generator is an emergency supply and this low powered light fitting is an emergency lighting), it does not light up normally. It will only turn on when there is an emergency (when the power fails)
Being rarely in operation, it is rarely noticed if the unit is no longer functional or not working. Or if it has been damaged or vandalized.
So being surface mounted gives a feeling that you will more likely notice if something goes wrong with the emergency light.
The original design for this building was originally surface mounted units. However, during the construction stage, some visiting architect commented that the light fittings have spoiled the beauty of the interior of the open office space and the emergency lighting should be using a concealed type.
Therefore, we changed this emergency light to the concealed one for the office and lift lobby areas. However, the rest of the building was still using the surface mounted types.
Below are a few of the photographs that I took. However, if your interest is just on electrical pictures, just go straight to this post, Free electric installation pictures. There you can see pictures from other posts, which may be difficult for you to dig out as they are scattered all over this blog.
Picture 1 – The emergency lighting unit at its final position
Picture 2 – A closer look of the mounting of the unit
Picture 3 – A side view to show how the EL light fits in to the ceiling panel
Picture 4 – A top view (above the ceiling panel) showing how the unit is fixed to the ceiling board
Picture 5 – Another rear view of the emergency light unit
Copyright http://electricalinstallationblog.blogspot.com/ Emergency light installation pics
As far as the choice of types of the EL light, I would personally prefer a surface mounted self-contained type. The one being installed in this picture is also a battery-backed self-contain type, but it is recessed mounted.
Being a technical guy, the surface mounted type of emergency lighting gives a certain feeling of comfort in my opinion. That is because you can see the whole unit right at the surface of the ceiling. As this lighting is intended for emergency (the failure of the mains supply can also be considered an form of emergency in my view because no high-rise building can operate without the mains supply. So, the standby electrical generator is an emergency supply and this low powered light fitting is an emergency lighting), it does not light up normally. It will only turn on when there is an emergency (when the power fails)
Being rarely in operation, it is rarely noticed if the unit is no longer functional or not working. Or if it has been damaged or vandalized.
So being surface mounted gives a feeling that you will more likely notice if something goes wrong with the emergency light.
The original design for this building was originally surface mounted units. However, during the construction stage, some visiting architect commented that the light fittings have spoiled the beauty of the interior of the open office space and the emergency lighting should be using a concealed type.
Therefore, we changed this emergency light to the concealed one for the office and lift lobby areas. However, the rest of the building was still using the surface mounted types.
Below are a few of the photographs that I took. However, if your interest is just on electrical pictures, just go straight to this post, Free electric installation pictures. There you can see pictures from other posts, which may be difficult for you to dig out as they are scattered all over this blog.
Picture 1 – The emergency lighting unit at its final position
Picture 2 – A closer look of the mounting of the unit
Picture 3 – A side view to show how the EL light fits in to the ceiling panel
Picture 4 – A top view (above the ceiling panel) showing how the unit is fixed to the ceiling board
Picture 5 – Another rear view of the emergency light unit
Copyright http://electricalinstallationblog.blogspot.com/ Emergency light installation pics
Friday, January 1, 2010
Hospital LV electrical installation
The low voltage (LV) electrical installation for a hospital is designed based on the size and complexities of the hospital to be constructed. A small hospital would only require simpler design similar to other types of electrical works in buildings.
However for large hospitals, or hospitals with sophisticated equipment to be installed, the electrical installation will become more complex because of the wide variety of functions that is provided in the hospital. This ranges from industrial requirements, specialized medical departments, nurses’ hostels, staff accommodation areas, operating theaters and laboratories.
Specials requirements of a hospital electrical design
A hospital deals with life and death of patients. Therefore there are special requirements that must be met by the electrical installation. The most important of these is probably the reliability of the electrical system that is being designed. Many patients rely on life saving equipment and procedures just to stay alive. Therefore, power supply failures longer than certain duration cannot be accepted. Some of the equipment cannot even tolerate a power interruption any more than a few seconds.
All these means that a hospital electrical installation needs to be designed with not just a reliable electrical system, but also with a highly dependable backup electric supply sources. The fact that the power supply to some equipment cannot even be interrupted for any longer than just a few seconds means that an Interruptible Power Supply (UPS) system is an absolute necessity.
Hospital’s electrical installation write-up below
The following is a write-up on the low voltage (LV) electrical installation for a 500-bed government hospital. I modified it from part of an early draft that I did for a turnkey proposal a few years ago. I did not include the high voltage part of the installation here because the treatment on a HV system will best be handled on its own in a separate post.
You may notice that I have managed to give more explanations in certain sections, while the others are very short. I will get back into these short sections when I can steal a little bit more time from my work to finish them.
A LITTLE MESSAGE FROM THE SPONSOR
After reading this post, if you can spare the time, check out the following link. It is a link on how to convert your car into an electric car at minimal cost. It is a way we in the electrical industry can contribute in the global effort to save this planet . In any case, it can save some significant dollars from our daily transport costs. Check it out. It’s a good reading.
A. Distribution system
Usually the major load centers of a large hospital would consist of the Hospital Complex, the Mechanical Plant, and the accommodation areas which are the Nurses’ Hostels and the Staff Quarters.
1. Accommodation area substation
The nurses’ hostels and the staff quarters are usually mentioned separately because the each unit of the staff quarters would be provided with a separate individual meter installed by the electric supply authority. The occupants will need to pay for the electricity bill themselves.
While the electricity cost of all the nurses hostels would be part of the bulk electricity bill charged by the supply company to the hospital. The nurses’ do not have to pay for the bill themselves. This is usually the arrangement made by government hospitals. Private hospitals may have different arrangements. However, the separately billed electric meters of the staff quarters are a standard practice at all hospitals as far as I know.
This separately billed meters for the staff quarters may seem a trivial issue, but from the design of the electrical distribution, in many cases this has made the design of the distribution system at the accommodation area more complicated.
I may dedicate a post in future just to discuss this topic, but for now I will not go further because that can distract us from the overall distribution system of the hospital electrical installation.
2. Mechanical plant substation
The mechanical plant is actually not just for the mechanical systems. It is generally a separate building that houses the central plants for almost all major mechanical and electrical services at the hospital complex. The maximum load current drawn by these plants are usually very large, therefore there require large switchgears, equipment and rooms needed to house them.
The mechanical plants for large hospitals are also massive in terms of physical sizes (for example, the chilled water system for the air-conditioning, the cooling towers, fire protection pumps and water tanks, etc). The machines and equipment at each of these plants can also be relatively noisy even during normal operation.
All these and the need for proper design to allow for easy maintenance require that a separate and dedicated plant building be allocated. A dedicated electrical substation is usually provided to handle all the loads inside the mechanical plant building.
3. Hospital complex substation
Many equipment inside the hospital complex require very large current and also very low impedance.
As the mechanical plant building is usually a distance away from the main hospital complex, a significant voltage drop is difficult to avoid if the supply center is located there. The low voltage cables needed to overcome this will be unnecessarily large and difficult to maneuver along the cable route. Not to mention the cost of these unnecessarily large low voltage cables and their support system.
Apart from that, some equipment such as the X-ray machines require very low impedance for proper operation.
These factors means that the substation (i.e. Hospital Substation) needed to supply the electrical loads inside the main hospital complex must be located close the local load center, which is inside the main hospital building itself. Feeder cables are looped to the Hospital Substation from the Mechanical Plant Substation at high voltage (usually at 11 kV).
How is the distribution system designed to make it reliable?
As the reliability of the electrical supply in a hospital can make a difference between life and death of some patients, an elaborate design effort is usually given to achieve this objective.
Foremost of all, the supply authority is usually requested to provide two incoming feeders to the hospital site. The purpose is so that if one incoming fails, the supply for the full load can be fed through the other feeder. Needless to say, these are high voltage feeders (usually 11 kV). Under normal operation, both feeders are usually in operation with each feeder supplying half of the load generally.
Some clients go as far as requiring that each of the high voltage feeders must not come from the same supply source in the authority’s local distribution network. This is to further reduce the downtime of incoming supply which some local distribution networks can fulfill and some not able to do so due to the limitations of their existing local distribution network.
Busbar couplers increase the electric supply reliability
In order to provide further flexibility, and therefore reliability, the arrangement of the busbars can be designed with a little bit more sophistication. For example, by providing separate busbars at suitable sections of a distribution center (e. the main switchboards, the downstream sub-switchboards, the standby diesel generator panels, the distribution board busbars, etc), the various sections of the busbars can be coupled with a switching system to direct the electric supply via alternative routes to critical areas and machines.
Reliability increased by the choice of distribution cables
The choice of the types of cables used in the distribution can also be used to increase reliability. The mineral insulated (MICC) cables give an added advantage of being a comparatively low impedance cable for a given size compared with other types of cables. This is a particularly important requirement for a supply to x-ray machines.
Use metal-clad busducts where possible
The metal enclosed busducts can also give significant further improvements because of its flexibility in allowing additional tappings at any point along the supply route without reducing the reliability of the supply feeder. Other types of cables would require an elaborate work and workmanship to provide the additional tappings, which can further reduce the reliability in the long run. It has been an established fact that many of faults on low voltage distribution feeders develop from these tapping locations.
A hospital’s backup power supply sources.
The strategies shown above on how to provide flexibility to the electrical distribution system will not deliver the reliability of the electric supply that it intends to if the causes of power failures come from the source of the supply, which is the authority’s local distribution network.
A hospital cannot take this chance. That is why a system of standby power supply sources are always designed for in the electrical installation of a hospital especially the large ones.
The standby power is used to allow the hospital to keep running its essential services during the mains fail. Normally fifty percent of the general lighting at the main hospital complex would be connected to the essential supply circuit so the light level is reduced to fifty percent. However this lighting level is still sufficient to allow the hospital to operate normally on a temporary basis.
Which socket outlets are connected to the hospital’s essential supply?
How many and which socket outlets (and other power points) are connected to the essential circuit are usually decided on a project to project basis. Normally during the design stages, the end users of the hospital being designed, which are usually the future staff for each department, would be called in for sessions of technical interaction with the hospital designers, architect and engineers.
In these sessions, the need of the users would be captured and incorporated into the design. These types of sessions can take thousands of hours for large hospitals. They are also highly technical and stressing sessions with parties from all sides clashing (I mean that in the construction management terms) with one another in trying to bring all the conflicting objectives to a compromise so that the designers can give a practical solution in the form of a design that can be built within the cost allocated.
Mechanical and electrical services for a hospital construction can easily come to 30 percent of the total construction cost. This does not yet include the cost of medical equipment and the IT system.
Sorry for the digression.
Similar to the power socket outlets, the air conditioning loads connected to the essential circuit are also usually decided on project to project basis with the aid of the information gathered during the interaction sessions described above.
Usually the central air conditioning system for a large hospital is provided with a smaller chiller (some people like to call it “baby chiller”). This chiller unit is chosen from a smaller capacity and it des not run during daytime operation. It will supply the load of the air conditioning system during very low load such as after midnight. Some machines may need to be air-conditioned 24 hors a day so the spaces housing these machines are supplied by the baby chiller during the low load periods. Therefore, this baby chiller may also be required to be connected to the essential supply circuit.
THE backup supply sources
These backup sources are almost always in the form of standby diesel automatic generators. These generators are usually located away from the main hospital building due to the level of noise produced during their operation. That is one of the reasons for a separate building to house the mechanical and electrical plants. So the “standby gensets” (another common words used to call this equipment) are housed inside the Mechanical Plant.
Uninterruptible Power Supply (UPS) System
As mentioned above, some equipment in the hospital cannot tolerate power supply failures at all when they are in use. So they are connected to the UPS system. The UPS system is in turn connected to the essential supply circuit, which is backed up by the standby generators.
One important point need to be noted with regards to the standby electrical generators. These generators are installed to fulfill two requirements. One is the operation requirements of the hospital which need some services to keep operating in the even of mains power failure. The other reason is the requirements of the Fire Department that some the fire system is fully operational in the event a fire case occurs during the absence of the mains supply which include also some lighting for evacuation purposes.
The Fire Department requirements on the standby electric generators
The Fire Department usually requires that the standby generators be up and supplying load within a few seconds (within 15 seconds the last time I checked, if I remember it correctly. This number may vary slightly from country to country.) from the moment of mains failure. However in practice, some generators in some installations are up to this performance. It can take longer.
Even with 15 second blackout, some works in the hospital may be disrupted long enough to cause danger to patients. The prime examples are the procedures in the operation theatres (OT) and the patients who are continuously dependent on some live-saving machines.
The UPS batteries
Therefore the UPS system is installed to fill this 15-second gap. The batteries in the UPS system will be supplying power only for this 15-second period plus a few seconds more added inside the UPS system settings to make sure the electrical supply (the mains supply or the standby generator’s supply) is stable before the UPS storage batteries are switched out of the supply circuit (and back into the charging circuit).
That was the case when the standby generator is up and running within 15 seconds. What if it takes longer (never mind the fire regulations regarding this)? What if the generator actually fails to start? In can happen, and it does happen, as the case when the starting batteries fail to supply sufficient voltage after a few years because of negligence by the maintenance team.
I purposely drag this point longer just to emphasize it, just to stress on the critical function served by the UPS in the backup electric supply system of a hospital.
More points on the distribution system (which I will elaborate further soon)
1. A substation’s low voltage section consists of the Main Switchboard (MSB), the Essential Main Switchboard (EMSB) and a bus coupler. The EMSB board supplies the required essential lighting, power and critical equipment in the Hospital Complex. Part of it also will serve the mechanical load such as air condition, compressed air, vacuum system, and boiler and fire protection system.
2. Local UPS will be provided to support the emergency power requirements of critical loads.
3. The normal, essential and emergency supplies will have separate main switchboard, sub-switchboard and distribution board to supply the respective lighting, power and mechanical services.
4. All switchboards and distribution boards will be provided with suitable types of protection. The sheet metal materials of the board enclosures will be of electro-galvanized type.
5. The design will provide at least 20% spare capacities in all switchboard and distribution boards for future needs, while the main switchboards will be provided with a spare capacity of 30 percent. The main switchboard of the hospital complex will be installed with an automatic power factor board and capacitor bank to keep power factor of the installation at not less than 0.85 lagging in any load condition.
6. A power monitoring system will be installed at the incomers. They will monitor the incomers for all the important electrical parameters including harmonic and also load shedding of non-essential loads. It will also be able to communicate with remote stations by any microprocessor.
7. One bulk electricity meter is provided for the hospital complex including the staff accommodation buildings. Separate meters will be provided for the retail spaces, the cafeteria, canteen, kitchen area, staff quarters and any other spaces for hospital functions that are planned for privatization by the hospital management.
However, as the detailed design develops, a separate bulk meter taking a supply at low voltage from the authority may be provided for the staff quarters, nurses’ hostels and housemen mess.
The reason being the limit set by the authority that any new site with load demand bigger than 5 MVA are required to surrender an empty 100 feet by 100 feet substation space for a future 33/11 kV substation.
At present, the estimated maximum demand for the whole complex including the accommodation area is 5.5 MVA, which has exceeded the % MVA limit.
As the detailed design is developed deeper, in tandem with the gradually more information available on the end-user requirements from the Client-Contractor interaction sessions, the expected maximum demand may be trimmed to below 5 MVA.
If it cannot be trimmed down to below 5 MVA, the application of supply that will be submitted to the electric supply authority will request two bulk meters: one HV bulk meter for 4.8 MVA that will supply both the Hospital Substation and the Mechanical Plant Substation.
The other will be an LV bulk meter for 700 kVA at the Accommodation area Substation which will provide supply to all the accommodation buildings.
Many times the authority approved this arrangement. However, there have also been cases where these types of arrangement were rejected.
B. Cabling and wiring
1. Normal, essential and emergency circuits should be installed in separate trunking and conduits. They need all be properly labeled.
2. All cabling and wiring should be in G.I. conduit. All trunking / tray / ladders shall be of unpainted electro-galvanized sheet metal and marked with proper a color coding system.
C. Electrical socket outlets
Minimum two 13A switched socket outlets should be provided for each bed in the normal wards whereby one of them is connected to essential supply.
Isolators should be provided to suffice the requirement of all equipment.
D. Fans
1. In buildings or rooms where air-conditioning is not provided such as at certain selected wards and at the residential buildings, fans should be installed as required.
2. The sweep fans provided should be complete with speed controls, located at the entry door.
E. Lighting installation
1. A hospital is a very complex, task-intensive institution. The selection of lighting services and control gears should be on the basis of functional aspects, energy efficient, good color rendition and low maintenance.
2. The lighting for various areas should be designed in the compliance with IES, DHSS and current Work Ministry’s code of practice to achieve the average illumination levels as described in attached schedule (will be uploaded later).
3. Labor room, Procedure room, Autopsy room and Treatment room should have the ceiling mounted examination light 0f 30000 lux.
Electrical HV switchgear installation pictures for hospitals
Below you may find some pictures (Well, only one for now.) on electrical installation in hospitals. I may upload more of them in future when I come back to finish on the short sections remaining in this post. So stay tuned.
P/S: You can also see quite a number of electrical installation pictures that I have uploaded at this post: Temporary electrical installations
Picture 1 - Hospital HV switchgear installation in progress
Picture 2 - HV switchgear installation - Rear view
Copyright http://electricalinstallationblog.blogspot.com/ - Hospital LV electrical installation
However for large hospitals, or hospitals with sophisticated equipment to be installed, the electrical installation will become more complex because of the wide variety of functions that is provided in the hospital. This ranges from industrial requirements, specialized medical departments, nurses’ hostels, staff accommodation areas, operating theaters and laboratories.
Specials requirements of a hospital electrical design
A hospital deals with life and death of patients. Therefore there are special requirements that must be met by the electrical installation. The most important of these is probably the reliability of the electrical system that is being designed. Many patients rely on life saving equipment and procedures just to stay alive. Therefore, power supply failures longer than certain duration cannot be accepted. Some of the equipment cannot even tolerate a power interruption any more than a few seconds.
All these means that a hospital electrical installation needs to be designed with not just a reliable electrical system, but also with a highly dependable backup electric supply sources. The fact that the power supply to some equipment cannot even be interrupted for any longer than just a few seconds means that an Interruptible Power Supply (UPS) system is an absolute necessity.
Hospital’s electrical installation write-up below
The following is a write-up on the low voltage (LV) electrical installation for a 500-bed government hospital. I modified it from part of an early draft that I did for a turnkey proposal a few years ago. I did not include the high voltage part of the installation here because the treatment on a HV system will best be handled on its own in a separate post.
You may notice that I have managed to give more explanations in certain sections, while the others are very short. I will get back into these short sections when I can steal a little bit more time from my work to finish them.
A LITTLE MESSAGE FROM THE SPONSOR
After reading this post, if you can spare the time, check out the following link. It is a link on how to convert your car into an electric car at minimal cost. It is a way we in the electrical industry can contribute in the global effort to save this planet . In any case, it can save some significant dollars from our daily transport costs. Check it out. It’s a good reading.
A. Distribution system
Usually the major load centers of a large hospital would consist of the Hospital Complex, the Mechanical Plant, and the accommodation areas which are the Nurses’ Hostels and the Staff Quarters.
1. Accommodation area substation
The nurses’ hostels and the staff quarters are usually mentioned separately because the each unit of the staff quarters would be provided with a separate individual meter installed by the electric supply authority. The occupants will need to pay for the electricity bill themselves.
While the electricity cost of all the nurses hostels would be part of the bulk electricity bill charged by the supply company to the hospital. The nurses’ do not have to pay for the bill themselves. This is usually the arrangement made by government hospitals. Private hospitals may have different arrangements. However, the separately billed electric meters of the staff quarters are a standard practice at all hospitals as far as I know.
This separately billed meters for the staff quarters may seem a trivial issue, but from the design of the electrical distribution, in many cases this has made the design of the distribution system at the accommodation area more complicated.
I may dedicate a post in future just to discuss this topic, but for now I will not go further because that can distract us from the overall distribution system of the hospital electrical installation.
2. Mechanical plant substation
The mechanical plant is actually not just for the mechanical systems. It is generally a separate building that houses the central plants for almost all major mechanical and electrical services at the hospital complex. The maximum load current drawn by these plants are usually very large, therefore there require large switchgears, equipment and rooms needed to house them.
The mechanical plants for large hospitals are also massive in terms of physical sizes (for example, the chilled water system for the air-conditioning, the cooling towers, fire protection pumps and water tanks, etc). The machines and equipment at each of these plants can also be relatively noisy even during normal operation.
All these and the need for proper design to allow for easy maintenance require that a separate and dedicated plant building be allocated. A dedicated electrical substation is usually provided to handle all the loads inside the mechanical plant building.
3. Hospital complex substation
Many equipment inside the hospital complex require very large current and also very low impedance.
As the mechanical plant building is usually a distance away from the main hospital complex, a significant voltage drop is difficult to avoid if the supply center is located there. The low voltage cables needed to overcome this will be unnecessarily large and difficult to maneuver along the cable route. Not to mention the cost of these unnecessarily large low voltage cables and their support system.
Apart from that, some equipment such as the X-ray machines require very low impedance for proper operation.
These factors means that the substation (i.e. Hospital Substation) needed to supply the electrical loads inside the main hospital complex must be located close the local load center, which is inside the main hospital building itself. Feeder cables are looped to the Hospital Substation from the Mechanical Plant Substation at high voltage (usually at 11 kV).
How is the distribution system designed to make it reliable?
As the reliability of the electrical supply in a hospital can make a difference between life and death of some patients, an elaborate design effort is usually given to achieve this objective.
Foremost of all, the supply authority is usually requested to provide two incoming feeders to the hospital site. The purpose is so that if one incoming fails, the supply for the full load can be fed through the other feeder. Needless to say, these are high voltage feeders (usually 11 kV). Under normal operation, both feeders are usually in operation with each feeder supplying half of the load generally.
Some clients go as far as requiring that each of the high voltage feeders must not come from the same supply source in the authority’s local distribution network. This is to further reduce the downtime of incoming supply which some local distribution networks can fulfill and some not able to do so due to the limitations of their existing local distribution network.
Busbar couplers increase the electric supply reliability
In order to provide further flexibility, and therefore reliability, the arrangement of the busbars can be designed with a little bit more sophistication. For example, by providing separate busbars at suitable sections of a distribution center (e. the main switchboards, the downstream sub-switchboards, the standby diesel generator panels, the distribution board busbars, etc), the various sections of the busbars can be coupled with a switching system to direct the electric supply via alternative routes to critical areas and machines.
Reliability increased by the choice of distribution cables
The choice of the types of cables used in the distribution can also be used to increase reliability. The mineral insulated (MICC) cables give an added advantage of being a comparatively low impedance cable for a given size compared with other types of cables. This is a particularly important requirement for a supply to x-ray machines.
Use metal-clad busducts where possible
The metal enclosed busducts can also give significant further improvements because of its flexibility in allowing additional tappings at any point along the supply route without reducing the reliability of the supply feeder. Other types of cables would require an elaborate work and workmanship to provide the additional tappings, which can further reduce the reliability in the long run. It has been an established fact that many of faults on low voltage distribution feeders develop from these tapping locations.
A hospital’s backup power supply sources.
The strategies shown above on how to provide flexibility to the electrical distribution system will not deliver the reliability of the electric supply that it intends to if the causes of power failures come from the source of the supply, which is the authority’s local distribution network.
A hospital cannot take this chance. That is why a system of standby power supply sources are always designed for in the electrical installation of a hospital especially the large ones.
The standby power is used to allow the hospital to keep running its essential services during the mains fail. Normally fifty percent of the general lighting at the main hospital complex would be connected to the essential supply circuit so the light level is reduced to fifty percent. However this lighting level is still sufficient to allow the hospital to operate normally on a temporary basis.
Which socket outlets are connected to the hospital’s essential supply?
How many and which socket outlets (and other power points) are connected to the essential circuit are usually decided on a project to project basis. Normally during the design stages, the end users of the hospital being designed, which are usually the future staff for each department, would be called in for sessions of technical interaction with the hospital designers, architect and engineers.
In these sessions, the need of the users would be captured and incorporated into the design. These types of sessions can take thousands of hours for large hospitals. They are also highly technical and stressing sessions with parties from all sides clashing (I mean that in the construction management terms) with one another in trying to bring all the conflicting objectives to a compromise so that the designers can give a practical solution in the form of a design that can be built within the cost allocated.
Mechanical and electrical services for a hospital construction can easily come to 30 percent of the total construction cost. This does not yet include the cost of medical equipment and the IT system.
Sorry for the digression.
Similar to the power socket outlets, the air conditioning loads connected to the essential circuit are also usually decided on project to project basis with the aid of the information gathered during the interaction sessions described above.
Usually the central air conditioning system for a large hospital is provided with a smaller chiller (some people like to call it “baby chiller”). This chiller unit is chosen from a smaller capacity and it des not run during daytime operation. It will supply the load of the air conditioning system during very low load such as after midnight. Some machines may need to be air-conditioned 24 hors a day so the spaces housing these machines are supplied by the baby chiller during the low load periods. Therefore, this baby chiller may also be required to be connected to the essential supply circuit.
THE backup supply sources
These backup sources are almost always in the form of standby diesel automatic generators. These generators are usually located away from the main hospital building due to the level of noise produced during their operation. That is one of the reasons for a separate building to house the mechanical and electrical plants. So the “standby gensets” (another common words used to call this equipment) are housed inside the Mechanical Plant.
Uninterruptible Power Supply (UPS) System
As mentioned above, some equipment in the hospital cannot tolerate power supply failures at all when they are in use. So they are connected to the UPS system. The UPS system is in turn connected to the essential supply circuit, which is backed up by the standby generators.
One important point need to be noted with regards to the standby electrical generators. These generators are installed to fulfill two requirements. One is the operation requirements of the hospital which need some services to keep operating in the even of mains power failure. The other reason is the requirements of the Fire Department that some the fire system is fully operational in the event a fire case occurs during the absence of the mains supply which include also some lighting for evacuation purposes.
The Fire Department requirements on the standby electric generators
The Fire Department usually requires that the standby generators be up and supplying load within a few seconds (within 15 seconds the last time I checked, if I remember it correctly. This number may vary slightly from country to country.) from the moment of mains failure. However in practice, some generators in some installations are up to this performance. It can take longer.
Even with 15 second blackout, some works in the hospital may be disrupted long enough to cause danger to patients. The prime examples are the procedures in the operation theatres (OT) and the patients who are continuously dependent on some live-saving machines.
The UPS batteries
Therefore the UPS system is installed to fill this 15-second gap. The batteries in the UPS system will be supplying power only for this 15-second period plus a few seconds more added inside the UPS system settings to make sure the electrical supply (the mains supply or the standby generator’s supply) is stable before the UPS storage batteries are switched out of the supply circuit (and back into the charging circuit).
That was the case when the standby generator is up and running within 15 seconds. What if it takes longer (never mind the fire regulations regarding this)? What if the generator actually fails to start? In can happen, and it does happen, as the case when the starting batteries fail to supply sufficient voltage after a few years because of negligence by the maintenance team.
I purposely drag this point longer just to emphasize it, just to stress on the critical function served by the UPS in the backup electric supply system of a hospital.
More points on the distribution system (which I will elaborate further soon)
1. A substation’s low voltage section consists of the Main Switchboard (MSB), the Essential Main Switchboard (EMSB) and a bus coupler. The EMSB board supplies the required essential lighting, power and critical equipment in the Hospital Complex. Part of it also will serve the mechanical load such as air condition, compressed air, vacuum system, and boiler and fire protection system.
2. Local UPS will be provided to support the emergency power requirements of critical loads.
3. The normal, essential and emergency supplies will have separate main switchboard, sub-switchboard and distribution board to supply the respective lighting, power and mechanical services.
4. All switchboards and distribution boards will be provided with suitable types of protection. The sheet metal materials of the board enclosures will be of electro-galvanized type.
5. The design will provide at least 20% spare capacities in all switchboard and distribution boards for future needs, while the main switchboards will be provided with a spare capacity of 30 percent. The main switchboard of the hospital complex will be installed with an automatic power factor board and capacitor bank to keep power factor of the installation at not less than 0.85 lagging in any load condition.
6. A power monitoring system will be installed at the incomers. They will monitor the incomers for all the important electrical parameters including harmonic and also load shedding of non-essential loads. It will also be able to communicate with remote stations by any microprocessor.
7. One bulk electricity meter is provided for the hospital complex including the staff accommodation buildings. Separate meters will be provided for the retail spaces, the cafeteria, canteen, kitchen area, staff quarters and any other spaces for hospital functions that are planned for privatization by the hospital management.
However, as the detailed design develops, a separate bulk meter taking a supply at low voltage from the authority may be provided for the staff quarters, nurses’ hostels and housemen mess.
The reason being the limit set by the authority that any new site with load demand bigger than 5 MVA are required to surrender an empty 100 feet by 100 feet substation space for a future 33/11 kV substation.
At present, the estimated maximum demand for the whole complex including the accommodation area is 5.5 MVA, which has exceeded the % MVA limit.
As the detailed design is developed deeper, in tandem with the gradually more information available on the end-user requirements from the Client-Contractor interaction sessions, the expected maximum demand may be trimmed to below 5 MVA.
If it cannot be trimmed down to below 5 MVA, the application of supply that will be submitted to the electric supply authority will request two bulk meters: one HV bulk meter for 4.8 MVA that will supply both the Hospital Substation and the Mechanical Plant Substation.
The other will be an LV bulk meter for 700 kVA at the Accommodation area Substation which will provide supply to all the accommodation buildings.
Many times the authority approved this arrangement. However, there have also been cases where these types of arrangement were rejected.
B. Cabling and wiring
1. Normal, essential and emergency circuits should be installed in separate trunking and conduits. They need all be properly labeled.
2. All cabling and wiring should be in G.I. conduit. All trunking / tray / ladders shall be of unpainted electro-galvanized sheet metal and marked with proper a color coding system.
C. Electrical socket outlets
Minimum two 13A switched socket outlets should be provided for each bed in the normal wards whereby one of them is connected to essential supply.
Isolators should be provided to suffice the requirement of all equipment.
D. Fans
1. In buildings or rooms where air-conditioning is not provided such as at certain selected wards and at the residential buildings, fans should be installed as required.
2. The sweep fans provided should be complete with speed controls, located at the entry door.
E. Lighting installation
1. A hospital is a very complex, task-intensive institution. The selection of lighting services and control gears should be on the basis of functional aspects, energy efficient, good color rendition and low maintenance.
2. The lighting for various areas should be designed in the compliance with IES, DHSS and current Work Ministry’s code of practice to achieve the average illumination levels as described in attached schedule (will be uploaded later).
3. Labor room, Procedure room, Autopsy room and Treatment room should have the ceiling mounted examination light 0f 30000 lux.
Electrical HV switchgear installation pictures for hospitals
Below you may find some pictures (Well, only one for now.) on electrical installation in hospitals. I may upload more of them in future when I come back to finish on the short sections remaining in this post. So stay tuned.
P/S: You can also see quite a number of electrical installation pictures that I have uploaded at this post: Temporary electrical installations
Picture 1 - Hospital HV switchgear installation in progress
Picture 2 - HV switchgear installation - Rear view
Copyright http://electricalinstallationblog.blogspot.com/ - Hospital LV electrical installation
Thursday, December 31, 2009
Electrical DB pictures
I have uploaded below a few pictures of electrical DB being installed at a high-rise office-building project. I only have enough time for these few pictures today, but I will be sending a more detailed post on the DB installation soon. Plus a few more of the DB pictures maybe.
In the meantime, if you have the time, check out the following link. It is a link on how to convert your car into an electric car at minimal cost. It is a way we in the electrical industry can contribute in the global effort to save this planet. In any case, it can save some significant dollars of our daily transport costs. Check it out. It’s a good reading.
Picture 1 – Mounting position and location
These electrical boards are permanent boards, not a temporary electrical installation. I have been sending so many pictures of temporary electrical installations that I feel the need to make that clear. Otherwise, some readers may get confused because in these pictures you can see that the boards and the cable trunking are solidly mounted on the concrete wall.
Actually there are three DB’s in this picture. The two big ones on the left (your left side) are the electrical distribution boards (DB) and the one at the far right is the telephone distribution panel (some people call it “DP panel”).
These DB’s are located along one of the corridors on the office floor. Therefore, they will need to be hidden from view and protected from unauthorized access. Therefore, a cabinet will be built around these boards, and a lockable door will be provided.
The installation work is in progress and the building is still under construction. However, if you see closely to the doors of the distribution boards, you may notice that the DB doors are not provided with lockable door handles. They seem to be provided only with door screws.
With this type of doors, then they are not protected from access to the live parts of the boards. So, if there is no provision to build such electrical cabinet or rooms as I have mentioned and secure it with lockable keys, then the construction supervisor in charge of the electrical installation must insist for it.
There is no problem in installing the distribution boards exposed like that. However, they must be protected from unauthorized access. In this case, you have three choices:
Provide lockable doors and raise the mounting height of the DB’s above reach by hands.
Raise the mounting heights to unreachable heights without providing the lockable keys to the doors. This a little bit of a compromise already, but some may say that is already okay. In many scenarios this sort of issues are quite subjective.
Build a cabinet around the boards, enclosing all three electrical and telephone boards. A lockable door should be installed.
Build wall around them so it will become an electrical rooms, plus a lockable door.
Picture 2 – Dropper trunking from above ceiling
This second picture shows the metal trunking coming down from above the ceiling and into the distribution boards.
Some of you may be wondering why these trunking are like that… with the big trunking branching into the smaller ones above the ceiling. The reason is to make the space bigger for the wiring cables to crisscross each other while coming out of the MCB’s (miniature circuit breakers) inside the DB’s and into its intended trunking route (either one or the three branch trunking above the ceiling.
Actually, the three branches of trunking above the ceiling is for the following:
One for lighting wiring final circuits. All wiring cables supplying all lights and maybe ceiling fans and toilet exhaust fans. This is an air-conditioned office building, and ceiling fans are not used at all. However, wiring for the air-conditioning equipment is not allowed to run in trunking for lighting wires. Emergency light and the lighted exit signs also have their wiring installed inside this trunking, but the one from the ESSENTIAL SUPPLY board.
I should have mentioned this earlier. We have two electrical DB’s there because one is supplied from the standby electrical generator. This is the smaller DB. The bigger DB is supplied from the authority’s mains supply. The one supplied form the standby electrical generator is usually called “essential DB” or “essential distribution board”, while the one supplied from the mains is normally called “normal DB” or normal distribution boards.
The Essential DB is usually smaller because the number of electrical loads it need to supply is smaller. In ordinary office buildings, the number of light fittings that need to be turned on during a power supply failure is usually only one out of three lights or about thirty percent of the general lighting. So the Essential DB will have only half the number of final circuit wiring as the Normal DB. That is why they are generally half the size, which is what you can see in this picture.
The second branch trunking is for the small power final circuit wiring, the wiring supplying all the switched socket outlets and other small power points like window air conditioners, etc. Cables supplying power to other mechanical equipment such as water pumps, etc are not allowed to share this trunking. The need to be installed in a separate trunking, which is the third branch trunking.
This carries the cables and wiring for the mechanical equipment like the building’s water pumps, etc.
So the above describes what those three branches of the metal trunking are for. The same applies for both DB.
Picture 3 – Bottom cable entry
This picture shows the bottom entry for cables. Both DB’s has bottom cable entry. Some of the readers may be wondering why cables need to enter the DB cabinet from both to and bottom. The reason being this is an office building with an underfloor trunking system.
The electrical socket outlets, the telephone socket and the computer data sockets for all office tables are provided from outlet boxes of this underfloor trunking system. So there are three separate high impact PVC trunking running inside the concrete floor throughout all office areas of this multi-storey office building. At each worktable, an outlet service of approximately 12 inch x 12-inch box is provided and all the power, telephone and data sockets are provided there.
You can see that the orange electrical trunking under the DB’s going downward to the floor. The green telephone DB also runs downward to the same location. This is where they are connected to the 3-way underfloor trunking system. The piece near the floor is called the “vertical access box” of the trunking system.
That is all on the bottom trunking for now. In future, I will talk more on the underfloor trunking system and maybe show you some real construction photos.
The top entry trunking are for all other cables and wiring. The wiring to the window air-conditioning units run above ceiling, never inside the underfloor trunking. The nature of underfloor trunking installation make it very difficult and messy to extend. You need to hack the concrete floor to install additional runs and that can disrupts the operation of the whole floor. So only the wiring for the final circuits to the office work desks are run inside them. They are dedicated only for this purpose most of the time.
Usually some general-purpose power sockets are still provided on the walls even where underfloor trunking system is used. These sockets are usually run in the above ceiling trunking and a dropper conduit is used to make the connection to the sockets on the walls.
The lighting wiring are always run inside the above ceiling trunking. A system of trunking and conduit is the dominant method for this wiring purpose in almost all office buildings.
From the above it is quite clear that a much larger number of wiring runs above tha ceiling than under the floor. So that is the reason the bottom entry trunking is much smaller than the top entry ones. In this case the bottom trunking from both DB’s can be joined and still use the same size to connect to the vertical access box.
Telephone DB
As for the telephone DB, the trunking does not need to run above ceiling to go to the sockets at the worktables. The top entry trunking is for the incoming multi-core telephone cable from the telephone riser shaft. All telephone final wiring cables run inside the underfloor trunking. Since this blog is about electrical matters only I will not talk too much on telephone works. That may be a topic for one of my new blogs.
Copyright http://electricalinstallationblog.blogspot.com/ Electrical DB pictures
In the meantime, if you have the time, check out the following link. It is a link on how to convert your car into an electric car at minimal cost. It is a way we in the electrical industry can contribute in the global effort to save this planet. In any case, it can save some significant dollars of our daily transport costs. Check it out. It’s a good reading.
Picture 1 – Mounting position and location
These electrical boards are permanent boards, not a temporary electrical installation. I have been sending so many pictures of temporary electrical installations that I feel the need to make that clear. Otherwise, some readers may get confused because in these pictures you can see that the boards and the cable trunking are solidly mounted on the concrete wall.
Actually there are three DB’s in this picture. The two big ones on the left (your left side) are the electrical distribution boards (DB) and the one at the far right is the telephone distribution panel (some people call it “DP panel”).
These DB’s are located along one of the corridors on the office floor. Therefore, they will need to be hidden from view and protected from unauthorized access. Therefore, a cabinet will be built around these boards, and a lockable door will be provided.
The installation work is in progress and the building is still under construction. However, if you see closely to the doors of the distribution boards, you may notice that the DB doors are not provided with lockable door handles. They seem to be provided only with door screws.
With this type of doors, then they are not protected from access to the live parts of the boards. So, if there is no provision to build such electrical cabinet or rooms as I have mentioned and secure it with lockable keys, then the construction supervisor in charge of the electrical installation must insist for it.
There is no problem in installing the distribution boards exposed like that. However, they must be protected from unauthorized access. In this case, you have three choices:
Provide lockable doors and raise the mounting height of the DB’s above reach by hands.
Raise the mounting heights to unreachable heights without providing the lockable keys to the doors. This a little bit of a compromise already, but some may say that is already okay. In many scenarios this sort of issues are quite subjective.
Build a cabinet around the boards, enclosing all three electrical and telephone boards. A lockable door should be installed.
Build wall around them so it will become an electrical rooms, plus a lockable door.
Picture 2 – Dropper trunking from above ceiling
This second picture shows the metal trunking coming down from above the ceiling and into the distribution boards.
Some of you may be wondering why these trunking are like that… with the big trunking branching into the smaller ones above the ceiling. The reason is to make the space bigger for the wiring cables to crisscross each other while coming out of the MCB’s (miniature circuit breakers) inside the DB’s and into its intended trunking route (either one or the three branch trunking above the ceiling.
Actually, the three branches of trunking above the ceiling is for the following:
One for lighting wiring final circuits. All wiring cables supplying all lights and maybe ceiling fans and toilet exhaust fans. This is an air-conditioned office building, and ceiling fans are not used at all. However, wiring for the air-conditioning equipment is not allowed to run in trunking for lighting wires. Emergency light and the lighted exit signs also have their wiring installed inside this trunking, but the one from the ESSENTIAL SUPPLY board.
I should have mentioned this earlier. We have two electrical DB’s there because one is supplied from the standby electrical generator. This is the smaller DB. The bigger DB is supplied from the authority’s mains supply. The one supplied form the standby electrical generator is usually called “essential DB” or “essential distribution board”, while the one supplied from the mains is normally called “normal DB” or normal distribution boards.
The Essential DB is usually smaller because the number of electrical loads it need to supply is smaller. In ordinary office buildings, the number of light fittings that need to be turned on during a power supply failure is usually only one out of three lights or about thirty percent of the general lighting. So the Essential DB will have only half the number of final circuit wiring as the Normal DB. That is why they are generally half the size, which is what you can see in this picture.
The second branch trunking is for the small power final circuit wiring, the wiring supplying all the switched socket outlets and other small power points like window air conditioners, etc. Cables supplying power to other mechanical equipment such as water pumps, etc are not allowed to share this trunking. The need to be installed in a separate trunking, which is the third branch trunking.
This carries the cables and wiring for the mechanical equipment like the building’s water pumps, etc.
So the above describes what those three branches of the metal trunking are for. The same applies for both DB.
Picture 3 – Bottom cable entry
This picture shows the bottom entry for cables. Both DB’s has bottom cable entry. Some of the readers may be wondering why cables need to enter the DB cabinet from both to and bottom. The reason being this is an office building with an underfloor trunking system.
The electrical socket outlets, the telephone socket and the computer data sockets for all office tables are provided from outlet boxes of this underfloor trunking system. So there are three separate high impact PVC trunking running inside the concrete floor throughout all office areas of this multi-storey office building. At each worktable, an outlet service of approximately 12 inch x 12-inch box is provided and all the power, telephone and data sockets are provided there.
You can see that the orange electrical trunking under the DB’s going downward to the floor. The green telephone DB also runs downward to the same location. This is where they are connected to the 3-way underfloor trunking system. The piece near the floor is called the “vertical access box” of the trunking system.
That is all on the bottom trunking for now. In future, I will talk more on the underfloor trunking system and maybe show you some real construction photos.
The top entry trunking are for all other cables and wiring. The wiring to the window air-conditioning units run above ceiling, never inside the underfloor trunking. The nature of underfloor trunking installation make it very difficult and messy to extend. You need to hack the concrete floor to install additional runs and that can disrupts the operation of the whole floor. So only the wiring for the final circuits to the office work desks are run inside them. They are dedicated only for this purpose most of the time.
Usually some general-purpose power sockets are still provided on the walls even where underfloor trunking system is used. These sockets are usually run in the above ceiling trunking and a dropper conduit is used to make the connection to the sockets on the walls.
The lighting wiring are always run inside the above ceiling trunking. A system of trunking and conduit is the dominant method for this wiring purpose in almost all office buildings.
From the above it is quite clear that a much larger number of wiring runs above tha ceiling than under the floor. So that is the reason the bottom entry trunking is much smaller than the top entry ones. In this case the bottom trunking from both DB’s can be joined and still use the same size to connect to the vertical access box.
Telephone DB
As for the telephone DB, the trunking does not need to run above ceiling to go to the sockets at the worktables. The top entry trunking is for the incoming multi-core telephone cable from the telephone riser shaft. All telephone final wiring cables run inside the underfloor trunking. Since this blog is about electrical matters only I will not talk too much on telephone works. That may be a topic for one of my new blogs.
Copyright http://electricalinstallationblog.blogspot.com/ Electrical DB pictures
Monday, December 28, 2009
How to install fire stops
The following provides sample specifications and it presents a guide on how to install fire stops inside buildings. During the installation work of electrical services inside buildings especially cables, cable sleeves, cable trays, conduit and trunking, walls and floors often need to be penetrated to allow for the route of these components to pass through.
After installation of a wiring trunking through a wall for example, the gaps between the wall opening and the trunking need to be sealed back. Where the trunking passes through fire compartment walls, it is also usually the requirements of the Fire Department that the inside of the trunking be sealed properly to prevent fire smoke from traveling between adjacent fire compartments.
The same applies to cable sleeves. The gaps between the cables and the pipe sleeve should also be properly applied with fire stop materials to form an effective fire barrier of the same fire rating as the wall being penetrated.
A. GENERAL
a. DESCRIPTION
To supply, install and test a fire-stopping system that comply with the requirements of the Electricity and Gas Supply Board, and in accordance with the contract Documents.
b. SCOPE OF WORK
1.Firestop Compounds.
2. Damming Material.
3. Site Tests
c. SUBMITTALS
Prior to commencement of the work, the contractor is required to submit the following:
1. To submit shop drawings, product data and manufacturer’s installation instructions for all materials and prefabricated devices, providing descriptions sufficient for identification at the job site.
2. To submit shop drawings showing proposed material, reinforcements anchorage, fastenings and method of installation. Construction details shall accurately reflect actual job conditions.
3. To submit Material Safety Data Sheets with product delivered to job site.
4. Previous Installation Records.
d. QUALITY ASSURANCE
1. The installation of the fire stop system should conform to requirements of qualified designs or manufacturer approved modifications, as supported by engineering reports.
2. The installation of the fire stop materials and systems shall fulfill all the requirements specified by the contract Documents and meet all requirements of the Electricity and Gas Supply Board.
3. The contractor shall submit manufacturer’s product data, letter of certification, or certified laboratory test report that the material or combination of materials (fire stop system) meets the requirements specified as and in accordance with the applicable referenced standards.
4. The manufacturer of the materials should have been actively engaged in the manufacture and installation of fire stops for at least 10 years.
B. PRODUCTS
List of acceptable manufacturers:
1. Promat; 2. KBS; 3. Cape Durasteel; or other approved equivalent.
b. FIRESTOPS
1. Fire stop compounds should be provided for caulk, pour, trowel or pump application. Material must be capable of sealing openings around single or multiple ducts, cables, wire or conduits against fire, smoke and toxic gases, and maintaining rating with a thickness no greater than the structure.
2. The fire stop compound should not contain any solvents or inorganic fibers. The penetration seal material must be unaffected by moisture and must maintain the integrity of the floor or wall assembly for its rated time period when tested in accordance with the requirements of Electricity and Gas Supply Board or ASTM E814 (UL 1479). The system should have a classified rating of up to and including 3 hours.
4. The fire stop system shall consist of a material, or combination of materials, to retain the integrity of fire-rated construction by maintaining an effective barrier against the spread of flame, smoke or gases through penetrations in fire-rated barriers. It will be used in specific locations as follows:
i) Penetrations for the passage of duct, cable tray, conduit, and electrical busways and raceways through fire-rated vertical barriers (wall and partitions), horizontal barriers (floor slabs and floor/ceiling assemblies), and vertical services shafts.
ii) Locations shown specifically on the design drawings or where specified in other sections of these specifications.
iii) Damming material, shall be provided where required as per manufacturer’s recommendations.
c. MATERIALS
1. The fire stop materials or systems should be flexible enough to allow for normal movement of building structure and penetrating items without affecting the adhesion or integrity of the system.
2. The materials used should not require that the disposal of used containers be carried out as a hazardous waste.
3. The fire stop materials used should not use solvent materials that will free itself resulting the fire seal shrinking with time.
D. EXECUTION
a. DELIVERY AND STORAGE
1. The materials should be delivered to site in original unopened containers or packages bearing the manufacturer’s name, brand designation, product description and U.L. classification mark.
2. The delivery of the fire seal materials should be coordinated with scheduled installation dates so that the storage time at the construction site can be minimized.
3. All materials should be stored under cover and be protected from weather and damage in compliance with manufacturer’s requirements.
4. The contractor should comply with all safety procedures, precautions and remedies as recommended by the manufacturer or the existing bylaws applicable to handling of any hazardous materials if applicable.
b. EXAMINATION
1. Prior to commencement of work, examine the areas and conditions under which the work is to be performed. Notify the main Contractor in writing of conditions detrimental to proper and timely completion of the work.
2. Ensure that each opening is of a proper size and in a suitable condition for the application of the fire seal. Sometimes the gaps or opening to be sealed is too large for the materials to be applied simply and some form of reinforcements may be required. Guide and instructions from the manufactures should be strictly followed in these cases.
c. PREPARATION
1. The substrate should be properly cleaned and rid of dirt, dust, grease, oil, loose materials, rust or other matter that may affect a proper application or adhesion of the fire stopping materials.
2. Metal and glass surfaces should be cleaned with non-alcohol solvents.
d. INSTALLATION
1. All fire stop material should be installed in accordance with the design requirements and the manufacturer's instruction.
2. All openings, voids or holes resulted from the penetration for the electrical and mechanical services should be properly and completely sealed to form an effective barrier against smoke, water and air.
3. Certain sections of the project specifications may require that certain locations and parts of the work be installed with fire seals. It is the responsibility of the contractor to identify these locations and parts, and to coordinate with other trade contractors related to those parts of Work in order to provide a uniform system of fire stopping.
4. The installation work of the fire stop materials should be coordinated with other trade contractors so that the installation can be carried out after completion of the floor penetration but before covering or concealing of the openings commences.
5. When the ambient temperature of the surrounding exceeds the manufacturer's recommendation for installation of a specified fire stop material, then the installation must not proceed.
6. It is not the intention of a fire stop system to re-establish the structural integrity of a structure. The contractor should consult with the Engineer before coring or penetrating a load bearing structural assembly.
7. Fire stop systems are not designed to support live load or traffic. The contractor should consult with the Engineer if there is a reason to believe that these limitations may be violated for any reason.
e. CABLES
1. A cable pipe sleeve should be installed with the inside diameter large enough to accommodate the intended cable diameter.
2. Fire stop materials should be applied at each end of the pipe sleeve in such a way as to comply with the requirements of a U.L. approved or the requirements of the Electricity and Gas Supply Board.
3. Insulate pipes on each side of a wall and caulk all around the insulation at the joint of wall and insulation.
f. DIESEL GENERATOR EXHAUST PIPES
1. The sleeve for the generator exhaust pipes should be properly installed and with the diameter large enough to accommodate the insulation thickness of the pipes.
2. The fire stop material should be installed in such a way as to comply with a U.L. approved system or to the requirements of the Electricity and Gas Supply Board.
g. TESTS AND INSPECTION
The following visual inspection shall be carried out at each location that has been applied with fire stopping materials:
1. Only appropriate and suitable materials are used.
2. The fire stop materials should be continuously applied around all ducts or cables to for a complete and effective seal.
3. Proper adhesion of the fire stop materials to cables and ducts.
Copyright http://electricalinstallationblog.blogspot.com/ - How to install fire stops
After installation of a wiring trunking through a wall for example, the gaps between the wall opening and the trunking need to be sealed back. Where the trunking passes through fire compartment walls, it is also usually the requirements of the Fire Department that the inside of the trunking be sealed properly to prevent fire smoke from traveling between adjacent fire compartments.
The same applies to cable sleeves. The gaps between the cables and the pipe sleeve should also be properly applied with fire stop materials to form an effective fire barrier of the same fire rating as the wall being penetrated.
A. GENERAL
a. DESCRIPTION
To supply, install and test a fire-stopping system that comply with the requirements of the Electricity and Gas Supply Board, and in accordance with the contract Documents.
b. SCOPE OF WORK
1.Firestop Compounds.
2. Damming Material.
3. Site Tests
c. SUBMITTALS
Prior to commencement of the work, the contractor is required to submit the following:
1. To submit shop drawings, product data and manufacturer’s installation instructions for all materials and prefabricated devices, providing descriptions sufficient for identification at the job site.
2. To submit shop drawings showing proposed material, reinforcements anchorage, fastenings and method of installation. Construction details shall accurately reflect actual job conditions.
3. To submit Material Safety Data Sheets with product delivered to job site.
4. Previous Installation Records.
d. QUALITY ASSURANCE
1. The installation of the fire stop system should conform to requirements of qualified designs or manufacturer approved modifications, as supported by engineering reports.
2. The installation of the fire stop materials and systems shall fulfill all the requirements specified by the contract Documents and meet all requirements of the Electricity and Gas Supply Board.
3. The contractor shall submit manufacturer’s product data, letter of certification, or certified laboratory test report that the material or combination of materials (fire stop system) meets the requirements specified as and in accordance with the applicable referenced standards.
4. The manufacturer of the materials should have been actively engaged in the manufacture and installation of fire stops for at least 10 years.
B. PRODUCTS
List of acceptable manufacturers:
1. Promat; 2. KBS; 3. Cape Durasteel; or other approved equivalent.
b. FIRESTOPS
1. Fire stop compounds should be provided for caulk, pour, trowel or pump application. Material must be capable of sealing openings around single or multiple ducts, cables, wire or conduits against fire, smoke and toxic gases, and maintaining rating with a thickness no greater than the structure.
2. The fire stop compound should not contain any solvents or inorganic fibers. The penetration seal material must be unaffected by moisture and must maintain the integrity of the floor or wall assembly for its rated time period when tested in accordance with the requirements of Electricity and Gas Supply Board or ASTM E814 (UL 1479). The system should have a classified rating of up to and including 3 hours.
4. The fire stop system shall consist of a material, or combination of materials, to retain the integrity of fire-rated construction by maintaining an effective barrier against the spread of flame, smoke or gases through penetrations in fire-rated barriers. It will be used in specific locations as follows:
i) Penetrations for the passage of duct, cable tray, conduit, and electrical busways and raceways through fire-rated vertical barriers (wall and partitions), horizontal barriers (floor slabs and floor/ceiling assemblies), and vertical services shafts.
ii) Locations shown specifically on the design drawings or where specified in other sections of these specifications.
iii) Damming material, shall be provided where required as per manufacturer’s recommendations.
c. MATERIALS
1. The fire stop materials or systems should be flexible enough to allow for normal movement of building structure and penetrating items without affecting the adhesion or integrity of the system.
2. The materials used should not require that the disposal of used containers be carried out as a hazardous waste.
3. The fire stop materials used should not use solvent materials that will free itself resulting the fire seal shrinking with time.
D. EXECUTION
a. DELIVERY AND STORAGE
1. The materials should be delivered to site in original unopened containers or packages bearing the manufacturer’s name, brand designation, product description and U.L. classification mark.
2. The delivery of the fire seal materials should be coordinated with scheduled installation dates so that the storage time at the construction site can be minimized.
3. All materials should be stored under cover and be protected from weather and damage in compliance with manufacturer’s requirements.
4. The contractor should comply with all safety procedures, precautions and remedies as recommended by the manufacturer or the existing bylaws applicable to handling of any hazardous materials if applicable.
b. EXAMINATION
1. Prior to commencement of work, examine the areas and conditions under which the work is to be performed. Notify the main Contractor in writing of conditions detrimental to proper and timely completion of the work.
2. Ensure that each opening is of a proper size and in a suitable condition for the application of the fire seal. Sometimes the gaps or opening to be sealed is too large for the materials to be applied simply and some form of reinforcements may be required. Guide and instructions from the manufactures should be strictly followed in these cases.
c. PREPARATION
1. The substrate should be properly cleaned and rid of dirt, dust, grease, oil, loose materials, rust or other matter that may affect a proper application or adhesion of the fire stopping materials.
2. Metal and glass surfaces should be cleaned with non-alcohol solvents.
d. INSTALLATION
1. All fire stop material should be installed in accordance with the design requirements and the manufacturer's instruction.
2. All openings, voids or holes resulted from the penetration for the electrical and mechanical services should be properly and completely sealed to form an effective barrier against smoke, water and air.
3. Certain sections of the project specifications may require that certain locations and parts of the work be installed with fire seals. It is the responsibility of the contractor to identify these locations and parts, and to coordinate with other trade contractors related to those parts of Work in order to provide a uniform system of fire stopping.
4. The installation work of the fire stop materials should be coordinated with other trade contractors so that the installation can be carried out after completion of the floor penetration but before covering or concealing of the openings commences.
5. When the ambient temperature of the surrounding exceeds the manufacturer's recommendation for installation of a specified fire stop material, then the installation must not proceed.
6. It is not the intention of a fire stop system to re-establish the structural integrity of a structure. The contractor should consult with the Engineer before coring or penetrating a load bearing structural assembly.
7. Fire stop systems are not designed to support live load or traffic. The contractor should consult with the Engineer if there is a reason to believe that these limitations may be violated for any reason.
e. CABLES
1. A cable pipe sleeve should be installed with the inside diameter large enough to accommodate the intended cable diameter.
2. Fire stop materials should be applied at each end of the pipe sleeve in such a way as to comply with the requirements of a U.L. approved or the requirements of the Electricity and Gas Supply Board.
3. Insulate pipes on each side of a wall and caulk all around the insulation at the joint of wall and insulation.
f. DIESEL GENERATOR EXHAUST PIPES
1. The sleeve for the generator exhaust pipes should be properly installed and with the diameter large enough to accommodate the insulation thickness of the pipes.
2. The fire stop material should be installed in such a way as to comply with a U.L. approved system or to the requirements of the Electricity and Gas Supply Board.
g. TESTS AND INSPECTION
The following visual inspection shall be carried out at each location that has been applied with fire stopping materials:
1. Only appropriate and suitable materials are used.
2. The fire stop materials should be continuously applied around all ducts or cables to for a complete and effective seal.
3. Proper adhesion of the fire stop materials to cables and ducts.
Copyright http://electricalinstallationblog.blogspot.com/ - How to install fire stops
Electrical generator site tests
Upon completion of the site installation work for the standby electrical generator, the generator should be tested again to ensure that it is working properly. There are always some possibilities that some damages have occurred to the electrical generator during transporting process including loading and unloading. Also some damages may have happened during the storage at the construction site and during the installation work itself.
The following tests need to be carried on the permanent installation of the unit. The manufacturer of the generator should send their representative to do the tests. A report recording each item of the testing shall be certified by the manufacturer and submitted to the Engineer.
All calculations to derive performance data shall be made strictly in accordance with formulae given in the relevant standards. Any alterations or deviations from the relevant standard test layout or formula shall be subject to the prior approval of the Engineer.
The formulae used for correcting test results to site conditions shall be subjected to the Engineer's approval and be given with the test results together with calibration details of any measuring instruments.
A. Diesel Engine
a. The set shall be started and run from cold in the presence of the Engineer and loaded to its full load shop rating in the minimum time stated in the Schedule of Technical Data.
b. Thereafter the engine shall be kept at 50% of the full load (FL) current and 85% FL for 11/2 hours each, and then at its full rated output continuously for a period of 5 hours followed by a 10% overload run of 1 hour duration.
c. The following functional cheeks shall be undertaken during the tests, including but not limited to:-
1. The ability of the starting system to perform in accordance with the specified requirements.
2. Uninterrupted continuous operation at the loads stated earlier.
3. The correct functioning of the over speed safety devices.
4. The ability of malfunction protection and warning devices to respond correctly to the fault conditions under which they should operate. For example, low lubricating oil pressure, high lubricating oil temperatures, high coolant temperatures, etc.
5. The dynamic and steady characteristics of the governing system in accordance with BS 5515. This shall include the full load rejection test, speed droop test at 20% load reducing from full load to zero load and over speed test.
6. The functioning of all automatic pressure and temperature control.
B. Engine inspection after tests
The Engineer reserves the right to request the Sub- Contractor to strip the engine for examination and selected parts for inspection without cleaning and exactly as taken from the engine. Any part examined by the Engineer and deemed needing replacement shall be replaced by the Contractor without any additional cost.
C. Leak test
The storage tanks shall be subjected to a test pressure of 0.66 bar ( 10 psi ) for a period of 1 hour on site to the approval of the Engineer. Compressed air or dry nitrogen may be used for the pressure test. It is not permissible to use water for on-site testing.
All piping after installation shall also be pressure tested to 15 bars for a period of one hour during which the leakage shall be zero.
D. Alternator
a. Visual inspection
Location.
Terminal marking, rating plate and danger signs.
Finishes, lifting lugs, etc.
Mounting of engine and generator set.
Cabling system.
Earthing and terminating arrangement.
Lubrication system
Sleeve bearings (where applicable).
b. Dielectric test
c. Insulation resistance test.
d. Functional (Sequence) Test
Operation of AVR
Operation of neutral earthing switches.
Operation of all indicating and metering devices.
Operation of all alarm devices.
e. Noise level measurement
f. Angular velocity (rpm) check
g. Phase rotation check
Copyright http://electricalinstallationblog.blogspot.com/ Electrical generator site tests
The following tests need to be carried on the permanent installation of the unit. The manufacturer of the generator should send their representative to do the tests. A report recording each item of the testing shall be certified by the manufacturer and submitted to the Engineer.
All calculations to derive performance data shall be made strictly in accordance with formulae given in the relevant standards. Any alterations or deviations from the relevant standard test layout or formula shall be subject to the prior approval of the Engineer.
The formulae used for correcting test results to site conditions shall be subjected to the Engineer's approval and be given with the test results together with calibration details of any measuring instruments.
A. Diesel Engine
a. The set shall be started and run from cold in the presence of the Engineer and loaded to its full load shop rating in the minimum time stated in the Schedule of Technical Data.
b. Thereafter the engine shall be kept at 50% of the full load (FL) current and 85% FL for 11/2 hours each, and then at its full rated output continuously for a period of 5 hours followed by a 10% overload run of 1 hour duration.
c. The following functional cheeks shall be undertaken during the tests, including but not limited to:-
1. The ability of the starting system to perform in accordance with the specified requirements.
2. Uninterrupted continuous operation at the loads stated earlier.
3. The correct functioning of the over speed safety devices.
4. The ability of malfunction protection and warning devices to respond correctly to the fault conditions under which they should operate. For example, low lubricating oil pressure, high lubricating oil temperatures, high coolant temperatures, etc.
5. The dynamic and steady characteristics of the governing system in accordance with BS 5515. This shall include the full load rejection test, speed droop test at 20% load reducing from full load to zero load and over speed test.
6. The functioning of all automatic pressure and temperature control.
B. Engine inspection after tests
The Engineer reserves the right to request the Sub- Contractor to strip the engine for examination and selected parts for inspection without cleaning and exactly as taken from the engine. Any part examined by the Engineer and deemed needing replacement shall be replaced by the Contractor without any additional cost.
C. Leak test
The storage tanks shall be subjected to a test pressure of 0.66 bar ( 10 psi ) for a period of 1 hour on site to the approval of the Engineer. Compressed air or dry nitrogen may be used for the pressure test. It is not permissible to use water for on-site testing.
All piping after installation shall also be pressure tested to 15 bars for a period of one hour during which the leakage shall be zero.
D. Alternator
a. Visual inspection
Location.
Terminal marking, rating plate and danger signs.
Finishes, lifting lugs, etc.
Mounting of engine and generator set.
Cabling system.
Earthing and terminating arrangement.
Lubrication system
Sleeve bearings (where applicable).
b. Dielectric test
c. Insulation resistance test.
d. Functional (Sequence) Test
Operation of AVR
Operation of neutral earthing switches.
Operation of all indicating and metering devices.
Operation of all alarm devices.
e. Noise level measurement
f. Angular velocity (rpm) check
g. Phase rotation check
Copyright http://electricalinstallationblog.blogspot.com/ Electrical generator site tests
Wednesday, December 23, 2009
Temporary site floodlights
Large construction sites usually need temporary floodlight towers (in addition to the temporary lighting inside the new buildings) to provide lighting efficiently for the general movement, safety and security on the external areas of buildings under construction.
xxxxxxx RELATED PICTURES: High mast flood lighting | Temporary lighting installation xxxxxx
The lighting towers will usually takes the form of fixed tower or mobile tower units. Which one to use usually depends on the siting positions available for the lighting tower units and the duration of the contract.
For contracts with construction periods of relatively short durations, it may be much more economical to use mobile tower units.
However, if contract period is long, then it may be worth some considerations to use fixed height tower units. In any case, the fixed height towers can still be reused on future projects.
Careful dismantle the fixed height static towers at the end of the contract. Then the only extra materials that are required in at the next construction site is the foundation.
Static floodlighting tower units are normally available up to 18 meter high. They can be powered from the mains supply and they can be provided with their own electric generator.
The external areas of a construction site usually need a lighting level of around 20 lux average. This is the level sufficient of for the handling of construction materials and site clearing works.
A rectangular area of 60 meter by 60 meter can be lighted up to this light level by a typical 18 m tower carrying four units of 400 watt high pressure sodium fittings.
A main contractor with larger contracts and relatively longer contract period may want to consider a more elaborate study on their site lighting requirements.
If there is enough space to mount these floodlighting tower units, a proper lighting engineering study can be carried out together with the overall temporary electrical installation. The exercise would employ the floodlight lamp data, the aiming angles of the light fittings, and the mounting heights of the individual fittings to arrive at the required overall Illuminance.
These static towers would normally employ high intensity luminaries and with the type of equipment available today, the contractor can now light areas to sufficient level so the works can continue in evenings of the darker months. This is significant because it can considerably reduce the contract time.
Light fittings used in this application would necessarily be high intensity discharge type and the high pressure sodium lantern have become the more dominant type due to its high lighting output per kW of power usage (approximately 125 lumens per watt). A tungsten halogen lamp would give only 22 lumen per watt. The capital cost of opting the hight pressure sodium equipment is considerably higher than the tungsten halogen, but the main contractor may do well to consider other factors also such as the running cost, installation cost and the lamp life.
At the end of the construction work, all these equipment except the tower foundation, can be dismantled and transported to other project sites for reuse.
Below is a picture of a small mobile floodlight unit:
Picture 1 - Mobile site floodlight unit
Read more on site electrticity at this post, Temporary Electrical Installations.
There is also more imformation on temporary lighting at this post, Temporary lighting installation.
Copyright http://electricalinstallationblog.blogspot.com/ Temporary site floodlights
xxxxxxx RELATED PICTURES: High mast flood lighting | Temporary lighting installation xxxxxx
The lighting towers will usually takes the form of fixed tower or mobile tower units. Which one to use usually depends on the siting positions available for the lighting tower units and the duration of the contract.
For contracts with construction periods of relatively short durations, it may be much more economical to use mobile tower units.
However, if contract period is long, then it may be worth some considerations to use fixed height tower units. In any case, the fixed height towers can still be reused on future projects.
Careful dismantle the fixed height static towers at the end of the contract. Then the only extra materials that are required in at the next construction site is the foundation.
Static floodlighting tower units are normally available up to 18 meter high. They can be powered from the mains supply and they can be provided with their own electric generator.
The external areas of a construction site usually need a lighting level of around 20 lux average. This is the level sufficient of for the handling of construction materials and site clearing works.
A rectangular area of 60 meter by 60 meter can be lighted up to this light level by a typical 18 m tower carrying four units of 400 watt high pressure sodium fittings.
A main contractor with larger contracts and relatively longer contract period may want to consider a more elaborate study on their site lighting requirements.
If there is enough space to mount these floodlighting tower units, a proper lighting engineering study can be carried out together with the overall temporary electrical installation. The exercise would employ the floodlight lamp data, the aiming angles of the light fittings, and the mounting heights of the individual fittings to arrive at the required overall Illuminance.
These static towers would normally employ high intensity luminaries and with the type of equipment available today, the contractor can now light areas to sufficient level so the works can continue in evenings of the darker months. This is significant because it can considerably reduce the contract time.
Light fittings used in this application would necessarily be high intensity discharge type and the high pressure sodium lantern have become the more dominant type due to its high lighting output per kW of power usage (approximately 125 lumens per watt). A tungsten halogen lamp would give only 22 lumen per watt. The capital cost of opting the hight pressure sodium equipment is considerably higher than the tungsten halogen, but the main contractor may do well to consider other factors also such as the running cost, installation cost and the lamp life.
At the end of the construction work, all these equipment except the tower foundation, can be dismantled and transported to other project sites for reuse.
Below is a picture of a small mobile floodlight unit:
Picture 1 - Mobile site floodlight unit
Read more on site electrticity at this post, Temporary Electrical Installations.
There is also more imformation on temporary lighting at this post, Temporary lighting installation.
Copyright http://electricalinstallationblog.blogspot.com/ Temporary site floodlights
Temporary electric supply
What is a temporary electric supply?
A temporary electric supply is normally associated with the temporary electrical installation of a construction site. The term ‘temporary’ brings up a vision of a length of a length of twin and earth cable, or a four-core twisted cable and an undersized green earth wire, that is connected into a 30A single or 4-phase and neutral switch-fuse, trailing across the rough ground of the construction site to terminate into a seasoned self-fabricated distributed (with or without metal-clad enclosure).
On the so-called ‘distribution board’, a length of three flexible extension cord is connected to a clumsily assembled socket outlet with or without the use of a three-pin plug. How would you connect a three-core extension cord to a three-pin 13 A socket outlet? Somewhere on this blog, you can see clearly how it is done. It even has had various ways of doing it.
The extension cord run at high level near the soffit of floor slab, or some just run an the scattered floor to a temporary metalclad 13A switched socket outlet some 30 meters away.
The construction contract cost hundreds of millions, but the temporary electric supply system has been ‘engineered’ to fulfill all the site electrical requirements for the minimum price possible.
The main contractor has the responsibility to ensure the temporary electricity supply system installed is not only functional and meets all his electrical needs, but also safe for all involved in the construction work. The supply system need to be good enough to provide reliable power distribution, whether that period of the construction contract is three months or three years. Or whether the site supply requirement is 4 kVA or 3-megawatt supply.
What specifications to use for the temporary electric supply equipment?
Generally, what applied to low voltage installation is in the IEE Wiring regulations also apply to the temporary supply system. However two more British standards should be used to cover the gaps not covered there: BS 4363 (Specification for distribution units and electric supplies for construction sites and building sites) and BS 7375 (Code of practice for distribution of electricity in construction and building sites).
Source of the temporary supply
The temporary electric supply can be obtained from either the distribution network of the local electric supply authority or an independent electric generator installed at the site. Which one to use is usually just a matter of judgment on the cost involved.
However a few other factors may also need to be carefully considered which include practical problems that are usually associated with the distribution of the electric power safely and effectively throughout the site.
If the supply is taken from the local electric supply authority, a lead-time is usually required, as the authority would need time to arrange for the connection. The main contractor also need to submit sufficient details on the peak demand that will be required during the course of the contract, the positions of the point of supply intake and also the estimated contract period.
The authority usually requires enough details on the types and size of electrical load, e.g. lighting, heating, motors, etc. Motor loads usually need more details such as types of motors and the method of starting (direct-online, auto-transformer starting, etc).
Copyright http://electricalinstallationblog.blogspot.com/ Temporary electric supply
A temporary electric supply is normally associated with the temporary electrical installation of a construction site. The term ‘temporary’ brings up a vision of a length of a length of twin and earth cable, or a four-core twisted cable and an undersized green earth wire, that is connected into a 30A single or 4-phase and neutral switch-fuse, trailing across the rough ground of the construction site to terminate into a seasoned self-fabricated distributed (with or without metal-clad enclosure).
On the so-called ‘distribution board’, a length of three flexible extension cord is connected to a clumsily assembled socket outlet with or without the use of a three-pin plug. How would you connect a three-core extension cord to a three-pin 13 A socket outlet? Somewhere on this blog, you can see clearly how it is done. It even has had various ways of doing it.
The extension cord run at high level near the soffit of floor slab, or some just run an the scattered floor to a temporary metalclad 13A switched socket outlet some 30 meters away.
The construction contract cost hundreds of millions, but the temporary electric supply system has been ‘engineered’ to fulfill all the site electrical requirements for the minimum price possible.
The main contractor has the responsibility to ensure the temporary electricity supply system installed is not only functional and meets all his electrical needs, but also safe for all involved in the construction work. The supply system need to be good enough to provide reliable power distribution, whether that period of the construction contract is three months or three years. Or whether the site supply requirement is 4 kVA or 3-megawatt supply.
What specifications to use for the temporary electric supply equipment?
Generally, what applied to low voltage installation is in the IEE Wiring regulations also apply to the temporary supply system. However two more British standards should be used to cover the gaps not covered there: BS 4363 (Specification for distribution units and electric supplies for construction sites and building sites) and BS 7375 (Code of practice for distribution of electricity in construction and building sites).
Source of the temporary supply
The temporary electric supply can be obtained from either the distribution network of the local electric supply authority or an independent electric generator installed at the site. Which one to use is usually just a matter of judgment on the cost involved.
However a few other factors may also need to be carefully considered which include practical problems that are usually associated with the distribution of the electric power safely and effectively throughout the site.
If the supply is taken from the local electric supply authority, a lead-time is usually required, as the authority would need time to arrange for the connection. The main contractor also need to submit sufficient details on the peak demand that will be required during the course of the contract, the positions of the point of supply intake and also the estimated contract period.
The authority usually requires enough details on the types and size of electrical load, e.g. lighting, heating, motors, etc. Motor loads usually need more details such as types of motors and the method of starting (direct-online, auto-transformer starting, etc).
Copyright http://electricalinstallationblog.blogspot.com/ Temporary electric supply
Friday, December 18, 2009
Schools electrical installation
Electrical installation design for schools should be simple and economical. It must also be practical and functional.
Among the educational buildings, primary and secondary school buildings are the most common. Yet their numbers are still insufficient to cater for the high increase of enrollment throughout the country.
The construction of new school building by the education ministry has been increasing at a very high rate in the last few years. The design of the electrical system stresses more on the functionality and practicality of the system. The fundamental concept of the design is to ensure maximum safety and to keep maintenance requirements to the minimum. That also means that spare parts that will be needed for maintenance throughout the life of the installation should be easily obtainable locally and low-cost.
Other than the primary and secondary school building, the educational institution has the higher learning institutions such the universities technology institutes polytechnics, teachers training colleges and youth skills training centers.
These institutions have other criteria that set them apart from school building as educational buildings. In designing the electrical installations for these buildings, other that the factors of safety and functionality, special considerations should also be given to the factors of aesthetic values and the possibilities of future extension of the campuses or the building complexes.
Usually educational institutions like these consist of many separate large buildings like the administrative block, the staff quarters, the student hostel blocks, academic buildings, libraries, lecture theaters, halls and lecture halls. A few substations are usually required and they are usually located at large load centers throughout the campus.
These types of educational institutions usually have large campuses where many individual building are located far apart. As a consequence the electrical distribution system requires the use of higher distribution network. Proper switching arrangement between the various substations is usually designed for to ensure the continuity of supply and also to allow for ease of maintenance on the installation network.
A certain arrangement may also be worked out with the electricity supply authority regarding the design of the distribution and provisions of separate individual meters (which are separately billed by the electricity supplier i.e. canteen operators and retail shop operators) at certain facilities on the large campus.
Copyright http://electricalinstallationblog.blogspot.com/ Schools electrical installation
Among the educational buildings, primary and secondary school buildings are the most common. Yet their numbers are still insufficient to cater for the high increase of enrollment throughout the country.
The construction of new school building by the education ministry has been increasing at a very high rate in the last few years. The design of the electrical system stresses more on the functionality and practicality of the system. The fundamental concept of the design is to ensure maximum safety and to keep maintenance requirements to the minimum. That also means that spare parts that will be needed for maintenance throughout the life of the installation should be easily obtainable locally and low-cost.
Other than the primary and secondary school building, the educational institution has the higher learning institutions such the universities technology institutes polytechnics, teachers training colleges and youth skills training centers.
These institutions have other criteria that set them apart from school building as educational buildings. In designing the electrical installations for these buildings, other that the factors of safety and functionality, special considerations should also be given to the factors of aesthetic values and the possibilities of future extension of the campuses or the building complexes.
Usually educational institutions like these consist of many separate large buildings like the administrative block, the staff quarters, the student hostel blocks, academic buildings, libraries, lecture theaters, halls and lecture halls. A few substations are usually required and they are usually located at large load centers throughout the campus.
These types of educational institutions usually have large campuses where many individual building are located far apart. As a consequence the electrical distribution system requires the use of higher distribution network. Proper switching arrangement between the various substations is usually designed for to ensure the continuity of supply and also to allow for ease of maintenance on the installation network.
A certain arrangement may also be worked out with the electricity supply authority regarding the design of the distribution and provisions of separate individual meters (which are separately billed by the electricity supplier i.e. canteen operators and retail shop operators) at certain facilities on the large campus.
Copyright http://electricalinstallationblog.blogspot.com/ Schools electrical installation
Light switches installation
The installation of light switches and other electrical parts need to take into consideration a number of factors. For light switches, the following requirements must be incorporated into the design drawings and the specifications.
1) The grouping of lighting luminaries into single control should be done in small groups or on individual luminaries. This should be arranged in such a way that unnecessary lights can be switched off while allowing sufficient luminaries to be operating efficiently to give the required level of light over the working space where the activities is ongoing. This is part of the overall effort to lower the operating cost and conserve energy.
2) Where group switching are implemented, clear identification should be provided near the switch to indicate the lighting area controlled by a particular switch. For example, if a switch controls a number of light fittings over the main entrance of a lobby, then a label indicating “MAIN ENTRANCE” should be provided at the switch.
3) Switches should be provided at accessible locations that are within the line of sight from under the light fitting controlled. Exceptions to this are usually enclosed staircases and corridors used by the general public. For these areas, the location of the switches is selected to prevent abuse or unintentional operation by members of the public. Control of lighting for these types of spaces should be done by someone who is in authority over the area concerned.
In many cases these switches are located inside locked electrical rooms. In more advanced designs, these lights are controlled by a timer or the building control system so the lights are automatically switched on and off without human intervention. A manual bypass switch is usually provided where automatic controls are implemented.
In those parts of the world where the climates are seasonal, some form of sensors (eg. daylight sensor) is also commonly utilized.
4) The grouping of the lights should be so arranged that they can be switched off parallel to the windows. This will allow the row of lights nearer to the window can be switched off when the effect of daylight from outside the building is already adequate for the activities in the room.
5) Further control in the levels of lighting should arranged by the use of alternate switching. For example, in a row switching arrangement, alternate luminaries in the same row should be grouped under the same switch. In this way it is possible to switch off half the lights (thereby reducing half of the energy consumption) while maintaining a reasonable uniformity at the same time.
This method can be taken further by arranging the grouping to give a three or four lighting levels. For example, the corridor lighting at hospitals can be arranged into three alternate switching groups. After 7 pm one of the three groups of lights will be switched off, reducing the energy consumption by all corridor lights throughout the hospital by one third. That is a significant amount of kWh for large hospitals.
After midnight, the second group of lights will be switched off, reducing the consumption by a further one-third. That means after midnight only 33 percent of the corridor lights will be “ON”, and these lights are one of three alternately throughout all the corridors.
Copyright http://electricalinstallationblog.blogspot.com/ Light switches installation
1) The grouping of lighting luminaries into single control should be done in small groups or on individual luminaries. This should be arranged in such a way that unnecessary lights can be switched off while allowing sufficient luminaries to be operating efficiently to give the required level of light over the working space where the activities is ongoing. This is part of the overall effort to lower the operating cost and conserve energy.
2) Where group switching are implemented, clear identification should be provided near the switch to indicate the lighting area controlled by a particular switch. For example, if a switch controls a number of light fittings over the main entrance of a lobby, then a label indicating “MAIN ENTRANCE” should be provided at the switch.
3) Switches should be provided at accessible locations that are within the line of sight from under the light fitting controlled. Exceptions to this are usually enclosed staircases and corridors used by the general public. For these areas, the location of the switches is selected to prevent abuse or unintentional operation by members of the public. Control of lighting for these types of spaces should be done by someone who is in authority over the area concerned.
In many cases these switches are located inside locked electrical rooms. In more advanced designs, these lights are controlled by a timer or the building control system so the lights are automatically switched on and off without human intervention. A manual bypass switch is usually provided where automatic controls are implemented.
In those parts of the world where the climates are seasonal, some form of sensors (eg. daylight sensor) is also commonly utilized.
4) The grouping of the lights should be so arranged that they can be switched off parallel to the windows. This will allow the row of lights nearer to the window can be switched off when the effect of daylight from outside the building is already adequate for the activities in the room.
5) Further control in the levels of lighting should arranged by the use of alternate switching. For example, in a row switching arrangement, alternate luminaries in the same row should be grouped under the same switch. In this way it is possible to switch off half the lights (thereby reducing half of the energy consumption) while maintaining a reasonable uniformity at the same time.
This method can be taken further by arranging the grouping to give a three or four lighting levels. For example, the corridor lighting at hospitals can be arranged into three alternate switching groups. After 7 pm one of the three groups of lights will be switched off, reducing the energy consumption by all corridor lights throughout the hospital by one third. That is a significant amount of kWh for large hospitals.
After midnight, the second group of lights will be switched off, reducing the consumption by a further one-third. That means after midnight only 33 percent of the corridor lights will be “ON”, and these lights are one of three alternately throughout all the corridors.
Copyright http://electricalinstallationblog.blogspot.com/ Light switches installation
Emergency lights installation
The installation of self contained emergency lights is a statutory requirement in most countries. They need to be provided at strategic places throughout the building in order to aid the evacuation of the building occupants out of the building in the event of failure o the mains supply.
The need for these emergency lighting is real even during daytime because some internal corridors inside the building are actually too dark without some form of lighting. The emergency lights are meant to provide the minimum illuminance needed for a safe and orderly movement of the people.
The self contained emergency light fittings are usually installed at all exit routes and at all places where uninterrupted lighting is required. In the second situation this lights serve the dual functions of a fire related equipment and a normal lighting (with much reduced lighting level).
The emergency light fittings are connected to the essential supply of the building electrical system. This way the rechargeable storage battery is charged even during normal power failure (i.e. when the standby electrical generator is running).
The exact quantity and the exact locations of these emergency light fittings are usually recommended by the Fire Department. In practice, a licensed architect is required by law to submit the building design plans to the Fire Department for approval before the building construction commences.
The architect would need to incorporate these lighting into their fire protection design schemes in order to obtain the Fire Department’s approval.
This layout is part of what is normally called the “static fire protection”. Those services like the wet risers, etc are called active fire protection and they will need to be submitted by licensed professional mechanical engineers to the Fire Department after the passive fire protection schemes (submitted by the architects) have been approved.
Prior to the submission by the architect, the electrical engineer’s input may be requested by the architect with respect to the quantities and locations of the emergency lights. However this task has become so routine that the engineer’s advice on this aspect is rarely necessary.
After the approval has been obtained, the approved layout of the emergency lighting is binding and it has become an input and a minimum design requirement for the electrical engineer. She can add more of the emergency light fittings into the design, but she cannot omit or change what has been approved in the submitted drawings.
That is basically the principle.
In addition to the self contained emergency lights that are required by the fire department, some of the general lighting luminaries are also connected to the essential supply that has been backed by the standby generator. This is sometimes done to supplement the lighting provided by the self contained emergency lights.
More often, however, this is done to provide some level of general lighting that can allow normal work to continue even in the event of normal power failure. Of course power failures caused by fire conditions demand a different course of actions immediately from all the building occupants.
There is one more lighting component that is closely related to the self contained emergency lights, that is the “EXIT” sign.
The Exit signs are also required by law similar to the emergency lights. They must be provided at all exit doors of all buildings and all floors, and at each location where the fire emergency exit routes change direction.
Similar to the emergency lights, these components are included in the proposed static fire protection submitted by the architects to the Fire Department.
An approved layout of this fire component will become a minimum design requirement to the electrical engineer. She can add more of the lighted Exit signs, but she cannot reduce them or change them.
Like the emergency lights also, the Exit signs are self-contained, battery operated. The difference between the two is that the Exit signs are always on.
See pictures of electrical installations by visiting this post, Free electric installation pictures.
Copyright http://electricalinstallationblog.blogspot.com/ Emergency lighting installation
The need for these emergency lighting is real even during daytime because some internal corridors inside the building are actually too dark without some form of lighting. The emergency lights are meant to provide the minimum illuminance needed for a safe and orderly movement of the people.
The self contained emergency light fittings are usually installed at all exit routes and at all places where uninterrupted lighting is required. In the second situation this lights serve the dual functions of a fire related equipment and a normal lighting (with much reduced lighting level).
The emergency light fittings are connected to the essential supply of the building electrical system. This way the rechargeable storage battery is charged even during normal power failure (i.e. when the standby electrical generator is running).
The exact quantity and the exact locations of these emergency light fittings are usually recommended by the Fire Department. In practice, a licensed architect is required by law to submit the building design plans to the Fire Department for approval before the building construction commences.
The architect would need to incorporate these lighting into their fire protection design schemes in order to obtain the Fire Department’s approval.
This layout is part of what is normally called the “static fire protection”. Those services like the wet risers, etc are called active fire protection and they will need to be submitted by licensed professional mechanical engineers to the Fire Department after the passive fire protection schemes (submitted by the architects) have been approved.
Prior to the submission by the architect, the electrical engineer’s input may be requested by the architect with respect to the quantities and locations of the emergency lights. However this task has become so routine that the engineer’s advice on this aspect is rarely necessary.
After the approval has been obtained, the approved layout of the emergency lighting is binding and it has become an input and a minimum design requirement for the electrical engineer. She can add more of the emergency light fittings into the design, but she cannot omit or change what has been approved in the submitted drawings.
That is basically the principle.
In addition to the self contained emergency lights that are required by the fire department, some of the general lighting luminaries are also connected to the essential supply that has been backed by the standby generator. This is sometimes done to supplement the lighting provided by the self contained emergency lights.
More often, however, this is done to provide some level of general lighting that can allow normal work to continue even in the event of normal power failure. Of course power failures caused by fire conditions demand a different course of actions immediately from all the building occupants.
There is one more lighting component that is closely related to the self contained emergency lights, that is the “EXIT” sign.
The Exit signs are also required by law similar to the emergency lights. They must be provided at all exit doors of all buildings and all floors, and at each location where the fire emergency exit routes change direction.
Similar to the emergency lights, these components are included in the proposed static fire protection submitted by the architects to the Fire Department.
An approved layout of this fire component will become a minimum design requirement to the electrical engineer. She can add more of the lighted Exit signs, but she cannot reduce them or change them.
Like the emergency lights also, the Exit signs are self-contained, battery operated. The difference between the two is that the Exit signs are always on.
See pictures of electrical installations by visiting this post, Free electric installation pictures.
Copyright http://electricalinstallationblog.blogspot.com/ Emergency lighting installation
Thursday, December 17, 2009
Electrical MCCB installation
This section lays out the major performance requirements for the MCCB (moulded-case electrical circuit breakers) installation inside switchboards.
All moulded-case circuit breakers shall comply with IEC 60947-2.
All electrical MCCB shall be of moulded insulating material of good mechanical strength and non-tracking properties. The tripping mechanisms shall be calibrated in compliance with IEC standards at the factory and the breaker shall be sealed to prevent tampering.
The MCCB shall be so designed that when on tripped condition, the circuit breaker cannot be switched on unless it has been reset by switching it to the OFF position first. The operating condition (i.e. ON, OFF or TRIP) of the circuit breaker shall be clearly indicated. The construction and operation of the MCCB installation shall be such that if a fault occurs, all the poles of the breaker shall operate simultaneously to isolate and clear the fault efficiently and safely without any possible risk to the operator or to the installation.
Each MCCB shall incorporate a ‘trip-free’ mechanism to ensure the breaker cannot be held closed under fault conditions. The operating mechanism of the circuit breaker shall be hermetically sealed at the factory and all metallic parts associated with the operating mechanism shall be treated against rust and corrosion.
Bolt-in type solid neutral links shall be provided and fitted in the same compartment together with the phase poles.
Means shall be provided to padlock the MCCB in the ‘OFF’ position. Mechanical ‘ON/ OFF’ indicator operating in conjunction with the rotary type operating handle of the circuit breaker must be provided.
MCCBs supplying loads from switchboards connected to the emergency power system shall be provided with facilities for remote operation (OPEN and CLOSE) and auxiliary contacts for remote indication.
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All moulded-case circuit breakers shall comply with IEC 60947-2.
All electrical MCCB shall be of moulded insulating material of good mechanical strength and non-tracking properties. The tripping mechanisms shall be calibrated in compliance with IEC standards at the factory and the breaker shall be sealed to prevent tampering.
The MCCB shall be so designed that when on tripped condition, the circuit breaker cannot be switched on unless it has been reset by switching it to the OFF position first. The operating condition (i.e. ON, OFF or TRIP) of the circuit breaker shall be clearly indicated. The construction and operation of the MCCB installation shall be such that if a fault occurs, all the poles of the breaker shall operate simultaneously to isolate and clear the fault efficiently and safely without any possible risk to the operator or to the installation.
Each MCCB shall incorporate a ‘trip-free’ mechanism to ensure the breaker cannot be held closed under fault conditions. The operating mechanism of the circuit breaker shall be hermetically sealed at the factory and all metallic parts associated with the operating mechanism shall be treated against rust and corrosion.
Bolt-in type solid neutral links shall be provided and fitted in the same compartment together with the phase poles.
Means shall be provided to padlock the MCCB in the ‘OFF’ position. Mechanical ‘ON/ OFF’ indicator operating in conjunction with the rotary type operating handle of the circuit breaker must be provided.
MCCBs supplying loads from switchboards connected to the emergency power system shall be provided with facilities for remote operation (OPEN and CLOSE) and auxiliary contacts for remote indication.
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Electrical DB wiring
Following is a sample specifications for the wiring of an electrical DB. Refer the section on Electrical DB installation for specification details on the construction of distribution boards.
Photo 1 - Internal wiring of an electrical DB
Terminals for external conductors All conductor terminals shall be suitable for copper conductors.
All cable termination assemblies shall have facilities for entry of cables from both the top and the bottom of the distribution boards. Cable entries, cable clamping, earthing facilities and supporting devices that are provided shall be suitable for the type, size and number of the incoming cables.
The identification ferrules Both ends of each wiring conductor shall be provided with identification ferrules. The ferrules shall be made of an insulating material of a type not affected by oil or damp. The characters shall be suitably marked in black. (See photo here: Wiring identification ferrules)
The ferrules shall be of the continuous ring type. A slide-on type will not be acceptable. The markings shall be in accordance with the relevant manufacturer’s drawings.
The wiring cables The minimum allowable cross-sectional area of control cables shall be 1.0 mm.sq. Wiring cables with a cross-sectional area of 1.5 mm.sq or larger shall always be stranded. The secondary circuits of current transformers with a 5 A rating shall not be less than 2.5 mm.sq. Color-coding of all wiring shall be in accordance with IEC 60446. The color of earth wiring cables shall be green with yellow stripes.
Wiring between two terminals shall be continuous. Joints or interconnections at locations other than at terminals are not acceptable. All wiring cables shall be terminated at both ends at a connection terminal. As a minimum requirement, use shall be made of rail-mounted terminals (TS 32 rail assembly) of high-grade Melamine.
When different voltage levels are employed in a single DB enclosure, partitions shall be installed between the terminals of different voltages.
The wiring The wiring ends of stranded conductors which have to be connected into bus type of terminal contacts shall be provided with compression-type pre-insulated wire pins with insulation support.
When cable lugs are used, they shall be of a compression type. To accommodate and support the wiring cables, covered plastic trunking, channels, insulated tubes or plastic strips shall be used. Wiring cables shall never be mounted directly to a metal part of a distribution boards.
The space factor for channels shall never be less than 30 percent. Where supporting of a wiring cable is not feasible, the cable shall be as short as possible.
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Photo 1 - Internal wiring of an electrical DB
Terminals for external conductors All conductor terminals shall be suitable for copper conductors.
All cable termination assemblies shall have facilities for entry of cables from both the top and the bottom of the distribution boards. Cable entries, cable clamping, earthing facilities and supporting devices that are provided shall be suitable for the type, size and number of the incoming cables.
The identification ferrules Both ends of each wiring conductor shall be provided with identification ferrules. The ferrules shall be made of an insulating material of a type not affected by oil or damp. The characters shall be suitably marked in black. (See photo here: Wiring identification ferrules)
The ferrules shall be of the continuous ring type. A slide-on type will not be acceptable. The markings shall be in accordance with the relevant manufacturer’s drawings.
The wiring cables The minimum allowable cross-sectional area of control cables shall be 1.0 mm.sq. Wiring cables with a cross-sectional area of 1.5 mm.sq or larger shall always be stranded. The secondary circuits of current transformers with a 5 A rating shall not be less than 2.5 mm.sq. Color-coding of all wiring shall be in accordance with IEC 60446. The color of earth wiring cables shall be green with yellow stripes.
Wiring between two terminals shall be continuous. Joints or interconnections at locations other than at terminals are not acceptable. All wiring cables shall be terminated at both ends at a connection terminal. As a minimum requirement, use shall be made of rail-mounted terminals (TS 32 rail assembly) of high-grade Melamine.
When different voltage levels are employed in a single DB enclosure, partitions shall be installed between the terminals of different voltages.
The wiring The wiring ends of stranded conductors which have to be connected into bus type of terminal contacts shall be provided with compression-type pre-insulated wire pins with insulation support.
When cable lugs are used, they shall be of a compression type. To accommodate and support the wiring cables, covered plastic trunking, channels, insulated tubes or plastic strips shall be used. Wiring cables shall never be mounted directly to a metal part of a distribution boards.
The space factor for channels shall never be less than 30 percent. Where supporting of a wiring cable is not feasible, the cable shall be as short as possible.
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Temporary electrical switchboards
All electrical switchboards used on temporary electrical installations or building construction sites should be of substantial construction. Where they are installed in outdoor locations, the switchboards should be so constructed that safe operation is not impaired by the weather. This weatherproof criteria usually means an IP rating of not less than IP 65. When the doors are opened, the degree of protection to all live parts should be no less than IP 20.
The method used for installation must have provisions so the cables and flexible extension cords coming in and out of the boards can be properly supported.
The temporary switchboards should also be provided with a door and locking facility that comply to the requirements of the electricity supply authority. Door should be designed and attached in a manner that will not damage any flexible cords connected to the board, and should protect the switches from mechanical damage. The door should be provided with a sign stating ‘KEEP CLOSED’ – ‘LEADS THROUGH BOTTOM’.
The switchboard should have an insulated slot in the bottom for the passage of leads.
The temporary switchboard should be attached to a permanent wall or other suitable portable structure, which has been designed for the purpose. Pole or post-mounted switchboards should be fixed by means of coach screws or bolted.
If the switchboard is used to supply other sub-boards downstream, every sub-board should be provided with a clearly labeled main isolating switch.
Temporary lighting outlets should be in a separate section on the switchboard and they should be clearly identified as lighting circuits. To protect from electric shock, the supply to the temporary lighting section should be provided with 100 mA residual current device (RCD), while the supply to the temporary socket outlets section should be protected by an RCD or earth leakage circuit breaker (ELCB) of sensitivity not more than 30 mA.
If too many tools are connected at the same that results in frequent tripping of the shock protection device, then the supply should splitted into multiple sections or multiple distribution boards, with each section or DB protected by a 30 mA RCD. This will prevent the shock protection device from being defeated by workers whose works have been most inconvenienced by the frequent tripping.
The electrical contractor or nominated persons should ensure that all power circuits are isolated or made accessible so as to eliminate the risk of fire, electric shock or other injury to persons after completion of the daily work.
All temporary supply mains should be protected by a circuit breaker or H.R.C. fuses.
A clearance of at least 1200 mm should be maintained in front of all switchboards and if the switchboard is located in a room, a clearance of 700 mm minimum should be provided around the other three sides. If the switchboard is also provided with rear access, then the rear of the switchboard must also have a 1200 mm clearance minimum.
Temporary switchboard should be so located that the maximum lengths of the flexible cords do not cause excessive voltage drops and impairs the normal operation of electrical equipment and portable electric tools.
The switchboard should be properly earthed and the color-coding of the protective conductors shall be done in accordance with IEC 60646.
A main earth bar should be provided inside the switchboard and it shall be connected to the temporary electrical grounding using appropriate size earthing conductor. The cross-section of the conductor shall be sufficient to carry the rated short-time withstand current of the switchgear.
All metal parts of the switchboard cubicle, and the metal parts of the components that are mounted on the switchboard including door, relays, instruments, etc shall be earthed through branch connections to the earth bar.
Frames of the draw-out circuit breakers (if they are used) shall be connected to the earth bar through a substantial plug type contact.
All temporary electrical equipment and switchgears including the switchboards should be inspected and labeled regularly by a licensed competent person before their first use and every three months thereafter.
The details of the inspection should be recorded in a logbook for inspection purposes. The details recorded in the logbook should include but not limited to the following:
a) Date of the inspection.
b) Identification no of the equipment or switchboard inspected.
c) License number of the inspecting competent person.
d) Any repair required because of the inspection.
Inspection label or sticker should be attached to the inspected switchboard showing the date of the most recent inspection. This label should carry the verification signature of the endorsing competent person.
Repair works that are required by the inspection should be carried out without delay. If the required repairs are related to safe use of the temporary switchboard, they must be properly carried out before the board is put to further use.
There is also a more detailed article on temporary electrical installation at this post, Temporary Electrical Installations.
Copyright http://electricalinstallationblog.blogspot.com/ Temporary electrical switchboard
The method used for installation must have provisions so the cables and flexible extension cords coming in and out of the boards can be properly supported.
The temporary switchboards should also be provided with a door and locking facility that comply to the requirements of the electricity supply authority. Door should be designed and attached in a manner that will not damage any flexible cords connected to the board, and should protect the switches from mechanical damage. The door should be provided with a sign stating ‘KEEP CLOSED’ – ‘LEADS THROUGH BOTTOM’.
The switchboard should have an insulated slot in the bottom for the passage of leads.
The temporary switchboard should be attached to a permanent wall or other suitable portable structure, which has been designed for the purpose. Pole or post-mounted switchboards should be fixed by means of coach screws or bolted.
If the switchboard is used to supply other sub-boards downstream, every sub-board should be provided with a clearly labeled main isolating switch.
Temporary lighting outlets should be in a separate section on the switchboard and they should be clearly identified as lighting circuits. To protect from electric shock, the supply to the temporary lighting section should be provided with 100 mA residual current device (RCD), while the supply to the temporary socket outlets section should be protected by an RCD or earth leakage circuit breaker (ELCB) of sensitivity not more than 30 mA.
If too many tools are connected at the same that results in frequent tripping of the shock protection device, then the supply should splitted into multiple sections or multiple distribution boards, with each section or DB protected by a 30 mA RCD. This will prevent the shock protection device from being defeated by workers whose works have been most inconvenienced by the frequent tripping.
The electrical contractor or nominated persons should ensure that all power circuits are isolated or made accessible so as to eliminate the risk of fire, electric shock or other injury to persons after completion of the daily work.
All temporary supply mains should be protected by a circuit breaker or H.R.C. fuses.
A clearance of at least 1200 mm should be maintained in front of all switchboards and if the switchboard is located in a room, a clearance of 700 mm minimum should be provided around the other three sides. If the switchboard is also provided with rear access, then the rear of the switchboard must also have a 1200 mm clearance minimum.
Temporary switchboard should be so located that the maximum lengths of the flexible cords do not cause excessive voltage drops and impairs the normal operation of electrical equipment and portable electric tools.
The switchboard should be properly earthed and the color-coding of the protective conductors shall be done in accordance with IEC 60646.
A main earth bar should be provided inside the switchboard and it shall be connected to the temporary electrical grounding using appropriate size earthing conductor. The cross-section of the conductor shall be sufficient to carry the rated short-time withstand current of the switchgear.
All metal parts of the switchboard cubicle, and the metal parts of the components that are mounted on the switchboard including door, relays, instruments, etc shall be earthed through branch connections to the earth bar.
Frames of the draw-out circuit breakers (if they are used) shall be connected to the earth bar through a substantial plug type contact.
All temporary electrical equipment and switchgears including the switchboards should be inspected and labeled regularly by a licensed competent person before their first use and every three months thereafter.
The details of the inspection should be recorded in a logbook for inspection purposes. The details recorded in the logbook should include but not limited to the following:
a) Date of the inspection.
b) Identification no of the equipment or switchboard inspected.
c) License number of the inspecting competent person.
d) Any repair required because of the inspection.
Inspection label or sticker should be attached to the inspected switchboard showing the date of the most recent inspection. This label should carry the verification signature of the endorsing competent person.
Repair works that are required by the inspection should be carried out without delay. If the required repairs are related to safe use of the temporary switchboard, they must be properly carried out before the board is put to further use.
There is also a more detailed article on temporary electrical installation at this post, Temporary Electrical Installations.
Copyright http://electricalinstallationblog.blogspot.com/ Temporary electrical switchboard
Wednesday, December 16, 2009
Switchboard electrical earthing
Following is a picture showing the earthing busbar of a main switchboard. Below the picture is a simple performance specifications for the grounding of the switchboard.
The are also two more posts on switchboard installation check and switchboard electrical tests. The latter is a general list of tests and inspections that are usually required of a major switchboard such as main switchboards and large subswitchboards.
Photo 1 - Earthing busbar of a main switchboard (MSB)
The earthing of an electrical switchboard shall be in accordance with BS 7430, and the color coding of protective conductors shall be in accordance with IEC 60646.
Switchboard earthing busbar
The switchboard earthing busbar shall be installed internally along the full length of the switchboard. The material of the busbar shall be the same as the material of the phase busbars. (See more photos: Switchboard earthing busbar.)
Equipment earth bar
Where the substation consists of 11 kV switchgears, transformers and LV switchboards, earthing copper tape shall be installed continuously along the full length of the substation.
It shall be connected to the main system earth bar at both ends using appropriate size earthing bolts with nuts and spring washers.
The earthing copper tape shall be made of hard-drawn high conductivity copper.
The cross-section of the earth bar shall be sufficient to carry the rated short-time withstand current of the switchgear for the allowable temperature rise and the time specified.
Internal branch earth connections
The branch earth connections made from the switchboard earthing busbar to the individual switchboard components shall consist of adequately sized copper strips, or green/ yellow striped PVC sheathed stranded copper conductor.
The termination lugs shall be of the compression type.
Earthing of metal parts
All metal parts of a switchboard where live components (such as relays, instruments, indicating lights etc) are mounted shall be earthed through branch connections to the switchboard earthing busbar.
Doors of the switchboard shall also be similarly earthed.
Frames of the draw-out circuit breakers shall be connected to the earthing busbar through a substantial plug type earthing contact.
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The are also two more posts on switchboard installation check and switchboard electrical tests. The latter is a general list of tests and inspections that are usually required of a major switchboard such as main switchboards and large subswitchboards.
Photo 1 - Earthing busbar of a main switchboard (MSB)
The earthing of an electrical switchboard shall be in accordance with BS 7430, and the color coding of protective conductors shall be in accordance with IEC 60646.
Switchboard earthing busbar
The switchboard earthing busbar shall be installed internally along the full length of the switchboard. The material of the busbar shall be the same as the material of the phase busbars. (See more photos: Switchboard earthing busbar.)
Equipment earth bar
Where the substation consists of 11 kV switchgears, transformers and LV switchboards, earthing copper tape shall be installed continuously along the full length of the substation.
It shall be connected to the main system earth bar at both ends using appropriate size earthing bolts with nuts and spring washers.
The earthing copper tape shall be made of hard-drawn high conductivity copper.
The cross-section of the earth bar shall be sufficient to carry the rated short-time withstand current of the switchgear for the allowable temperature rise and the time specified.
Internal branch earth connections
The branch earth connections made from the switchboard earthing busbar to the individual switchboard components shall consist of adequately sized copper strips, or green/ yellow striped PVC sheathed stranded copper conductor.
The termination lugs shall be of the compression type.
Earthing of metal parts
All metal parts of a switchboard where live components (such as relays, instruments, indicating lights etc) are mounted shall be earthed through branch connections to the switchboard earthing busbar.
Doors of the switchboard shall also be similarly earthed.
Frames of the draw-out circuit breakers shall be connected to the earthing busbar through a substantial plug type earthing contact.
Note: This anchor post, Free electric installation pictures , may contain a summary of the materials you are looking for. It can be faster than clicking through each post title at the Blog Archive. I started it long ago but never actually got around to finish it.
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Switchboard electrical tests
The following electrical tests must be carried to all switchboards, sub-switchboards, main distribution boards and motor starter panels.
A. Full type tests
1) Full type tests shall be carried out in accordance with IEC 60439-1, IEC 60947-1, and IEC 60947-6-1. Certificates issued by approved independent testing laboratories shall be submitted to the Employer’s Representative.
The type tests shall include the following:
a) Verification of temperature-rise limits
b) Verification of the dielectric properties
c) Verification of the short-circuit withstand strength
d) Verification of the effectiveness of the prospective circuit
e) Verification of the clearances and creepage distances
f) Verification of mechanical operations
g) Verification of the degree of protection
B. Routine tests
Before the product leaves the works, the manufacturer shall carry out the relevant routine tests in accordance with IEC 60439-1 on the total assembly, and the IEC 60947-1 and IEC 60947-6-1 parts thereof when delivered with time intervals, and the results shall be recorded in a test report.
C. Special tests
Carry out the special tests recommended in IEC 1641 Guide for Testing Under Conditions of Arcing Due to Internal Fault, the result shall be recorded in a test report.
D. Acceptance Tests at Manufacturer’s Work
a) Acceptance tests shall be carried out on the completely assembled switchboards and motor starter panels. Transportable units can be wired together for the purpose of the tests instead of completing the busbar joints.
b) The tests and checks shall include, but not limited to, the following.
c) All the switchboards and motor starter panels shall be visually inspected for technical execution and conformity with the latest issue of approved drawings and the latest issue of the relevant standards. Spot checks shall be made to verify the following:
1) Dimensions
2) The degree of protection of enclosures
3) The degree of protection within compartments
4) The effectiveness and reliability of safety shutters, partitions and shrouds
5) The effectiveness and reliability of operating mechanisms, locks and interlock systems
6) The insulation of the busbar system
7) The creepage distances and clearances
8) The proper mounting of components
9) The internal wiring and cabling system
10) The correct wiring of main and auxiliary circuits
11) The suitability of clamping, earthing and terminating arrangements
12) The correct labeling of functional units
13) The completeness of the data on the nameplate
14) The availability of the earthing system throughout the switchgears
15) The interchangeability of electrically identical components
d) Dielectric tests shall be carried out in accordance with IEC 60439-1. The test voltage shall be at least:
1) For main circuits, 2500 Vac for 1 minute.
2) For control and auxiliary circuits, 2 x Un + 1000 Vac, with a minimum of 1500 Vac for 1 second.
e) Testing of the mechanical and electrical operation of a number of functional units on random basis, including their control and protective devices.
f) CT polarity, magnetization, ratio and burden measurements
g) Secondary injection tests
h) Primary injection tests
i) Painting and finishing tests:
1) Measurement of paint thickness.
2) Humidity (cyclic condensation) tests to BS 3900 Pt. F2. Painted panel shall withstand 1000 hours under test with no blistering of film and corrosion of base metal.
3) Adhesion test to ASTM D3359-02. Test tape shall not expose more than one 3 mm.sq of bare metal or underlying coating.
4) Impact resistance test to BS 3900 Pt. E7. Paint shall not chip off.
j) The manufacturer test shall be verified and witnessed by the Employer’s Representative or his representatives.
E. Site Tests
At the completion of the installation at site, each switchboard and motor starter panels shall be field tested by a representative of the manufacturer. A report recording each item of the tests shall be certified by the manufacturer and submitted to the Employer’s Representative.
a) Visual inspection
1) Correctness of location and mounting
2) Labeling, nameplates and markings.
3) Verification of torque for all nuts and bolts on busway.
4) Observation of cable bracing, both incoming and outgoing, certifying that it is in accordance with the manufacturer’s recommendations.
5) Safety shutters, partitions and shrouds.
6) Functional units, operating mechanisms, locks and interlock systems.
7) Mounting of components.
8) Internal wiring and cabling system.
9) Clamping, earthing and terminating arrangement.
10) Earthing system.
b) Dielectric tests shall be carried out in accordance with IEC 60439-1. The test voltages shall be at least:
1) For main circuits, 2500 Vac for 1 minute.
2) For control and auxiliary circuits, 2 x Un + 1000 Vac with a minimum of 1500V for 1 second.
c) Power frequency withstand voltage test.
d) CT polarity, magnetization, ratio and burden measurements.
e) Secondary injection test
f) Primary injection test
g) Functional / sequence test
i) Operation of each disconnecting means under load
ii) Operation of each automatic transfer switch
iii) Operation of all alarm devices
h) Mechanical operation test
i) Operation of each disconnecting means under load
ii) Operation of each auto transfer switch
iii) Operation of all interlocks
i) Calibration and setting of protection devices
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A. Full type tests
1) Full type tests shall be carried out in accordance with IEC 60439-1, IEC 60947-1, and IEC 60947-6-1. Certificates issued by approved independent testing laboratories shall be submitted to the Employer’s Representative.
The type tests shall include the following:
a) Verification of temperature-rise limits
b) Verification of the dielectric properties
c) Verification of the short-circuit withstand strength
d) Verification of the effectiveness of the prospective circuit
e) Verification of the clearances and creepage distances
f) Verification of mechanical operations
g) Verification of the degree of protection
B. Routine tests
Before the product leaves the works, the manufacturer shall carry out the relevant routine tests in accordance with IEC 60439-1 on the total assembly, and the IEC 60947-1 and IEC 60947-6-1 parts thereof when delivered with time intervals, and the results shall be recorded in a test report.
C. Special tests
Carry out the special tests recommended in IEC 1641 Guide for Testing Under Conditions of Arcing Due to Internal Fault, the result shall be recorded in a test report.
D. Acceptance Tests at Manufacturer’s Work
a) Acceptance tests shall be carried out on the completely assembled switchboards and motor starter panels. Transportable units can be wired together for the purpose of the tests instead of completing the busbar joints.
b) The tests and checks shall include, but not limited to, the following.
c) All the switchboards and motor starter panels shall be visually inspected for technical execution and conformity with the latest issue of approved drawings and the latest issue of the relevant standards. Spot checks shall be made to verify the following:
1) Dimensions
2) The degree of protection of enclosures
3) The degree of protection within compartments
4) The effectiveness and reliability of safety shutters, partitions and shrouds
5) The effectiveness and reliability of operating mechanisms, locks and interlock systems
6) The insulation of the busbar system
7) The creepage distances and clearances
8) The proper mounting of components
9) The internal wiring and cabling system
10) The correct wiring of main and auxiliary circuits
11) The suitability of clamping, earthing and terminating arrangements
12) The correct labeling of functional units
13) The completeness of the data on the nameplate
14) The availability of the earthing system throughout the switchgears
15) The interchangeability of electrically identical components
d) Dielectric tests shall be carried out in accordance with IEC 60439-1. The test voltage shall be at least:
1) For main circuits, 2500 Vac for 1 minute.
2) For control and auxiliary circuits, 2 x Un + 1000 Vac, with a minimum of 1500 Vac for 1 second.
e) Testing of the mechanical and electrical operation of a number of functional units on random basis, including their control and protective devices.
f) CT polarity, magnetization, ratio and burden measurements
g) Secondary injection tests
h) Primary injection tests
i) Painting and finishing tests:
1) Measurement of paint thickness.
2) Humidity (cyclic condensation) tests to BS 3900 Pt. F2. Painted panel shall withstand 1000 hours under test with no blistering of film and corrosion of base metal.
3) Adhesion test to ASTM D3359-02. Test tape shall not expose more than one 3 mm.sq of bare metal or underlying coating.
4) Impact resistance test to BS 3900 Pt. E7. Paint shall not chip off.
j) The manufacturer test shall be verified and witnessed by the Employer’s Representative or his representatives.
E. Site Tests
At the completion of the installation at site, each switchboard and motor starter panels shall be field tested by a representative of the manufacturer. A report recording each item of the tests shall be certified by the manufacturer and submitted to the Employer’s Representative.
a) Visual inspection
1) Correctness of location and mounting
2) Labeling, nameplates and markings.
3) Verification of torque for all nuts and bolts on busway.
4) Observation of cable bracing, both incoming and outgoing, certifying that it is in accordance with the manufacturer’s recommendations.
5) Safety shutters, partitions and shrouds.
6) Functional units, operating mechanisms, locks and interlock systems.
7) Mounting of components.
8) Internal wiring and cabling system.
9) Clamping, earthing and terminating arrangement.
10) Earthing system.
b) Dielectric tests shall be carried out in accordance with IEC 60439-1. The test voltages shall be at least:
1) For main circuits, 2500 Vac for 1 minute.
2) For control and auxiliary circuits, 2 x Un + 1000 Vac with a minimum of 1500V for 1 second.
c) Power frequency withstand voltage test.
d) CT polarity, magnetization, ratio and burden measurements.
e) Secondary injection test
f) Primary injection test
g) Functional / sequence test
i) Operation of each disconnecting means under load
ii) Operation of each automatic transfer switch
iii) Operation of all alarm devices
h) Mechanical operation test
i) Operation of each disconnecting means under load
ii) Operation of each auto transfer switch
iii) Operation of all interlocks
i) Calibration and setting of protection devices
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Electrical MCB installation
MCB installation (miniature circuit breakers) in the distribution boards shall comply with IEC 60898-1. They shall be incorporated with overcurrent protection. Their selection for use shall match their operating characteristics.
1. Type test certificates shall be produced for the MCB selected from international recognized testing laboratories.
2. Performance criteria
a) Breaking capacity
The rated short-circuit capacity, Icn, shall be higher or at least equal ot the maximum prospective short-circuit current at the points of installation as stated in the single-line drawings.
The rated service short-circuit capacity, Ics, of 6 kA and 10 kA breakers shall be 100 % Icn and 75 % Icn respectively.
b) Coordination
All MCB in the distribution boards shall be from the same manufacturer and total discrimination with the upstream breakers under over-current conditions shall be guaranteed. Details of the operating characteristics and the coordination with other protective devices shall be submitted to the Engineer for approval. The details shall include the manufacturer’s full current discrimination tables showing the over-current discrimination levels.
Back-up protection is permitted when a current limiting circuit breaker is installed in the upstream. Details of this coordination shall be submitted to the Engineer for approval. The details shall include the manufacturer’s back-up protection tables showing the upstream/ downstream devices and the coordinated level of protection.
c) Installation
The electrical MCB shall be fully rated for uninterrupted continuous service based on an ambient temperature of 30 degree Centigrade.
The MCB shall be of 35 mm DIN symmetrical rail type and available in one, two, three and four pole version.
The MCB shall be suitable for mounting in any positions with no derating.
3. Construction
a) Trip characteristics
The trip characteristics of the MCB shall be Type B, C or D as indicated in the drawings.
b) Operating mechanism
The operating mechanism shall be of the quick-make, quick-break type with the speed of operation independent of the operator. In addition, the breaker mechanism shall mechanically trip free from the operating handle so as to prevent the contacts from being held closed against short circuit and other abnormal conditions.
The operating mechanism shall be designed to operate all poles simultaneously during opening, closing and trip conditions. The individual operating mechanism of each pole of a multi-pole MCB shall be directly linked within the MCB and not only by the operating handles alone.
All MCB shall be tested for isolating function as stipulated in IEC 60898. The isolation function shall guarantee that the breakers when in open position, should have isolation distance in accordance with the requirements necessary to satisfy the need for users safety.
Means of positive contact identification to mimic the exact position of the contacts shall be provided. The indication of the open and closed position of the main contacts shall preferably be provided by the position of the actuator. Color-coded bands and lettering on the actuator shall be incorporated to aid identification.
The operating handle shall be of the toggle type with facility for installation of padlock device.
All MCB shall have optional field installable accessories like shunt-trip coil, under-voltage release, ON/ OFF indications, alarm switch, etc. The installation shall be flexible such that to allow for fitting of accessories to either the left or right side of the MCB.
All MCB must be suitable for remote controlled ON/ OFF operation via an electrical motor operator.
c) Terminals
The MCB shall have double function terminals to allow for correct termination of busbars and cables. The top terminal shall be suitable for PIN busbar, the bottom terminals shall be suitable for both PIN and FORK busbars.
The cable terminals shall be equipped with safety guards to protect against misconnection. The safety guards shall function in a manner such that there is only one possibility of cable insertion into the MCB terminals. This will eliminate all possibilities of loose cable terminations due to wrong insertions.
Copyright http://electricalinstallationblog.blogspot.com/ Electrical MCB installation
1. Type test certificates shall be produced for the MCB selected from international recognized testing laboratories.
2. Performance criteria
a) Breaking capacity
The rated short-circuit capacity, Icn, shall be higher or at least equal ot the maximum prospective short-circuit current at the points of installation as stated in the single-line drawings.
The rated service short-circuit capacity, Ics, of 6 kA and 10 kA breakers shall be 100 % Icn and 75 % Icn respectively.
b) Coordination
All MCB in the distribution boards shall be from the same manufacturer and total discrimination with the upstream breakers under over-current conditions shall be guaranteed. Details of the operating characteristics and the coordination with other protective devices shall be submitted to the Engineer for approval. The details shall include the manufacturer’s full current discrimination tables showing the over-current discrimination levels.
Back-up protection is permitted when a current limiting circuit breaker is installed in the upstream. Details of this coordination shall be submitted to the Engineer for approval. The details shall include the manufacturer’s back-up protection tables showing the upstream/ downstream devices and the coordinated level of protection.
c) Installation
The electrical MCB shall be fully rated for uninterrupted continuous service based on an ambient temperature of 30 degree Centigrade.
The MCB shall be of 35 mm DIN symmetrical rail type and available in one, two, three and four pole version.
The MCB shall be suitable for mounting in any positions with no derating.
3. Construction
a) Trip characteristics
The trip characteristics of the MCB shall be Type B, C or D as indicated in the drawings.
b) Operating mechanism
The operating mechanism shall be of the quick-make, quick-break type with the speed of operation independent of the operator. In addition, the breaker mechanism shall mechanically trip free from the operating handle so as to prevent the contacts from being held closed against short circuit and other abnormal conditions.
The operating mechanism shall be designed to operate all poles simultaneously during opening, closing and trip conditions. The individual operating mechanism of each pole of a multi-pole MCB shall be directly linked within the MCB and not only by the operating handles alone.
All MCB shall be tested for isolating function as stipulated in IEC 60898. The isolation function shall guarantee that the breakers when in open position, should have isolation distance in accordance with the requirements necessary to satisfy the need for users safety.
Means of positive contact identification to mimic the exact position of the contacts shall be provided. The indication of the open and closed position of the main contacts shall preferably be provided by the position of the actuator. Color-coded bands and lettering on the actuator shall be incorporated to aid identification.
The operating handle shall be of the toggle type with facility for installation of padlock device.
All MCB shall have optional field installable accessories like shunt-trip coil, under-voltage release, ON/ OFF indications, alarm switch, etc. The installation shall be flexible such that to allow for fitting of accessories to either the left or right side of the MCB.
All MCB must be suitable for remote controlled ON/ OFF operation via an electrical motor operator.
c) Terminals
The MCB shall have double function terminals to allow for correct termination of busbars and cables. The top terminal shall be suitable for PIN busbar, the bottom terminals shall be suitable for both PIN and FORK busbars.
The cable terminals shall be equipped with safety guards to protect against misconnection. The safety guards shall function in a manner such that there is only one possibility of cable insertion into the MCB terminals. This will eliminate all possibilities of loose cable terminations due to wrong insertions.
Copyright http://electricalinstallationblog.blogspot.com/ Electrical MCB installation
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