Posted by MRB

All secondary wiring shall be of not less than 1.5 sq. mm. section insulated with PVC and shall be fixed securely without strain by cleats of the compression type. All screws, locknuts, washers, bolts etc. shall be of copper alloy type.
Indicating lamps shall be long life coloured type. All indicating lamps shall be adequately ventilated and easily be replaced from the front of the panel without the use of extractors.
Instruments, meters, relays, protective fuses etc. located on the front of the switchboard shall be so positioned that as far as possible, each instrument, meter, relay, protective fuse etc. is adjacent to the unit which it is associated.All relays shall be of heavy duty type, unaffected by external vibration and capable of operation in any position. All instruments, meters, relays, equipment etc. shall be fully tropicalised.
One number approved anti-condensation heater shall be installed for every two sections at the switchboards. Each heater shall be complete with automatic thermostat control, ON-OFF switch and indicating lamp.
Engraved labels with white lettering on a black background shall be fastened or riveted on the front panels of each switchgear and item of equipment. The wording shall be approved by the S.O.’s Representative. Engraved name plate showing the relevant earth fault setting, overcurrent setting, currenttransformer ratio, fuse rating, name of the circuit to which it is connected, etc. shall be fixed to switchgear panels to which it refers.

All distribution boards and Consumer units shall be installed at locations indicated in the Drawings or as directed by the S.O.’s Representative. They shall comply with IEC 60439-3 and unless otherwise specified, shall be surface mounted metalclad type with hinged cover, rust-proof and finished with epoxy dry-powder and oven baked enamel grey. Knockouts or other approved form of cable entries and suitable brass earthing bolt and nut shall be provided.

The distribution board/consumer unit shall be equipped with HRC fuses or miniature circuit breakers (mcb) of rating as specified in the Drawings. HRC fuses shall comply with relevant parts of IEC 60269. Mcb shall have rupturing capacity not less than that indicated on Drawings and/or Bill of Quantities and shall comply with IEC 60898.
The metal surfaces adjacent to any live part and all spaces between phases shall be protected by insulation barriers. The busbars shall be hard drawn high conductivity copper. The current capacity of the busbars shall not be less than the sum of the maximum current ratings of all out-going circuits plus 20% spare capacity. The neutral and earth connection for each circuit shall be individually connected to the neutral and earth bar respectively. The sequence of termination of the neutral and earth wires shall correspond to that of phase circuit.
For consumer units, the switch shall be of double pole, air-break, toggle type provided with a handle having clear indication of ‘ON-OFF’ positions. The switch shall comply with IEC 60947-3 and have fully shrouded incoming cable terminals. The contacts shall be of long switching life type.Where surge protection device is specified, the device and its associated equipment shall be housed in separate compartment immediately after where the incoming switchgear is connected. Engraved labels with white lettering on a black background shall be fitted externally on the front cover of the distribution board/consumer unit describing its usage and with a suitable designation for identification.
Each distribution board/consumer unit shall be provided with a table stating details of each circuit. The details shall include fuse rating/mcb rating, cable size, number and type of loads etc. The description of each circuit printed thereon shall include the corresponding circuit number in the as installed schematic diagram. The table shall be printed on durable materials in such a manner as to be permanently legible protected by an acrylic docket and properly displayed on the inside cover of the distribution board/consumer unit.
All switchgears shall have voltage and frequency rating suitable for the power system to which they are connected. The current rating shall not be less than that specified in the Drawings and/or Bill of Quantities. They shall conform to the latest IEC Standards.


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