WIRING (SURFACE OR CONCEALED)
9.3 CONDUIT WIRING (SURFACE OR CONCEALED)
The cables used in conduit wiring shall, unless otherwise specified, be PVC insulated cable of 450/750 V grade to MS 136. The conductors shall be of stranded, plain annealed copper to MS 69 and MS 280. The insulation shall be suitable for continuous operation at a maximum cable temperature of 70 0C and comply with MS 138. Unless otherwise specified in the Drawings and/or Bill of Quantities, the conduits and conduit fittings shall be of galvanised steel. Cables above false ceiling shall be run in conduit or trunking as directed.
The conduit shall generally be run on the underside of the floor slab or suspended from the floor slabs by mild steel brackets or suspenders. The trunking shall be suspended from the floor slabs or mounted against the wall by mild steel brackets. The mild steel brackets shall be anti-rust treated, painted with a primer and finished in an orange enamel. The suspension structure shall be robust in constructions and adequately installed such that the conduit/trunking will not sag.
Conduit for lighting point shall be terminated in a junction box complete with die-cast cone-shaped metal cover so that downdrop to luminaire shall be carried out through flexible steel conduit up to the luminaire. Ceiling fan points shall be run in the similar way. Flexible conduit shall be used for termination to equipment, which are subjected to movement or vibration. However, the length of this flexible conduit shall not exceed 400 mm unless approved by the S.O.’s Representative.
For concealed conduit wiring, a spare conduit shall be provided from the distribution board to the ceiling space for future extension. The spare conduit shall be plugged at the ceiling end with removable plug. The number of cables drawn into the conduit or laid in trunking shall be such that the ratio of the sum of the overall cross-sectional areas of the cables (including insulation and any sheath) to the internal cross-sectional area of the conduit or trunking in which they are installed shall not exceed 40%.