Thursday, December 17, 2009

Electrical DB installation

The electrical DB (distribution boards) for high-rise office installations shall be non-ventilated, naturally cooled, metal enclosed type, flush fronted and suitable for front access and shall be built to comply with IEC 60439-1. All louvers shall be covered with wire mesh.

The distribution boards shall contain MCCB (moulded case circuit breakers), MCB (miniature circuit breakers), RCD (residual current devices) and busbars as indicated in the contract documents. The DB shall be suitable for wall mounting or floor mounting as appropriate.

All necessary fixing materials, mounting bolts, etc shall be provided for the type of mounting mentioned.

All operating devices shall be mounted for installation, cable termination and maintenance operation at the front of the panel.

All distribution panel located outside the riser and public area shall have key lock handle.

Enclosure and Degree of protection
The DB enclosures shall be fabricated from rolled steel angle sections and shall be self supporting when assembled, uniform in height and depth from front to back. Sheet steel used shall not be less than 2 mm thick, anti-rust coated steel plate.

The distribution board shall be rigidly constructed to be stand alone units without any possibility of sagging, deformation or warping.

The front covers of the DB shall be of hinged-door type. The front doors shall be provided with lockable push button type. The doors shall be arranged to seal onto the board frame by means of a non-perishable dust-proof material. The sealing material shall be synthetic rubber and not foam. Doors shall be effectively earthed to the fixed enclosure by braided straps. Cover bolts or nuts shall be retained in place when undone.

For all internal DB installation, the degree of protection for the DB enclosures as per IEC 60529 shall be at least IP 41. When the doors are opened, the degree of protection to all live parts shall be at least IP 20.

All the distribution panels shall have Form 1 construction in compliance with IEC 60439-1.

The incoming and outgoing cable entry on the distribution boards shall be protected with rubber material to prevent damage to the cables.

Selection of components
All components shall be standardized as far as practical and shall comply with relevant IEC publications.

Busbars for the DB shall be of plain hard-drawn, high-conductivity, electrolytic copper bars in accordance with BS EN 13601: 2002 and of adequate rectangular cross-section to carry continuously the specified current without overheating and shall be rigidly mounted on insulators so as to withstand any mechanical force to which they may be subjected under maximum fault condition.

The DB busbars shall be colored red, yellow, blue and black at appropriate points to distinguish the phases and neutral. No tapes shall be used.

Moulded case circuit breakers (MCCB)
Refer to the MCCB section for the details on MCCBs.

Type test certificates shall be produced for the MCCB selected from internationally recognized testing laboratories.

Miniature circuit breakers (MCB)
Refer to MCB section or details on MCBs.

Refer to Electrical DB Wiring section for details on the DB wiring.

Residual current devices
Residual current devices shall provided as indicated in the design drawings and construction drawings.

Refer to Protection, Metering and Control section for details.

Type test certificates shall be produced for the RCCB/ ELCB selected from an independent internationally recognized independent testing laboratories.

Finishing and painting
Refer Electrical DB paintwork section for details on finishing and painting of electrical DB.

Copyright Electrical DB installation

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