1. All cables, busbars trunkings and wiring accessories shall be obtained from approved manufactures and shall be manufactured and tested to the relevant British Standard Specifications and the requirements of the Local Testing Authority.
Multicore cables and busbars trunkings shall have colour identifications to distinguish between different phases, neutral and earth conductors.
Cables shall be delivered to site in unbroken coils with the original wrapping intact. Cables with kinks or abrasions shall be replaced at no extra cost.
Unless otherwise specified, conductors shall be copper with 98% minimum conductivity. They shall be stranded plain annealed type to BS 6360 where used for cables and hard drawn type to BS 159 where used for busbar trunkings.
Unless otherwise specified all cables shall be PVC sheated and electrical accessories made of high impact PVC materials where used in corrosive environments.
2. PVC and PVC/PVC cables shall be selected in accordance with the followings:-
i) Where used as final sub-circuits for lighting and power and with conductor sizes not exeeding 25 mm2, they shall be of 440 volt/250 volt insulation grade to BS 6004.
ii) Where used as mains circuits or where conductor sizes exceed 25 mm2, they shall be 600 volt/1000 volt insulation grade to BS 6346.
iii) They shall have insulation suitable for 70 Degree C conductor temperature and comply to BS 6746.
3. PVC Armoured cables shall be selected in accordance with the following:-
i) They shall be of 600 volt/1000 volt grade to BS 6346 and suitable for 70 degree C conductor temperature with insulation complying to BS 6746.
ii) Unless otherwise specified, the armouring shall be constructed of single layer of galvanised steel wires complying with BS 1442.
iii) They shall be multi-core type
4. Paper insulated cables shall be selected in accordance with the following:-
i) They shall be of 600 volt/1000 volt grade to BS 6480 : Part 1 and suitable for 80 degree C. conductor temperature.
ii) Unless otherwise specified, they shall be of lead sheath double steel tape armoured (PILCDSTA) type.
iii) Single core cables shall be of non-magnetic armouring type with lead alloy sheath.
iv) They shall be mass impregnated with non draining insulationg compounds (M.I.N.D.).
v) They shall have the manufacturer names, year of manufacture and voltage rating printed on the tape immediately under the metal sheath.
vi) Where used as underground cables, they shall have served with compound layers of fibrous material and bitumen. Where used indoors and exposed, they shall be finished with extruded PVC oversheath.
5. Mineral insulated cables shall be selected in accordance with the following:-
i) Unless otherwise specified, they shall be of copper sheath to BS 6207 : Part 1.
ii) Where used in final sub-circuit for lighting and power with conductor size of 100 mm2 and less, they shall be of 440 volt insulation grade.
iii) Where used as mains circuits or where conductor sizes exceed 100 mm2, they shall be of 660 volt insulation grade.
iv) Silicon rubber sleeve insulation shall be used to replace copper sheath stripped off near the terminations. Where terminations exceed 150 degree C, varnished glass fibre sleeve insulation shall be used to replaced the "stripped off" copper sheath.
v ) Terminations, unless otherwise specified shall be rated for 105 degree C.
6. XLPE armoured cables shall be selected in accordance with the following:-
i) They shall be of 600 Volt/1000 Volt grade to BS 5467 and suitable for 90 degree C conductor temperature.
ii) Insulated cores shall be cabled with suitable fillers in round shape and a binder tape shall be applied helically over the cable cores.
iii) Separation sheath shall be black PVC compound complying with ST2 and IEC 502.
iv) Armour shall consist of a single layer of galvanised steel wires (type SWA) for multicore cables and hard drawn Aluminium wires (AWA) of single core cables.
v) Outer sheath shall be black PVC compound complying with ST2 of IEC 502.
vi) ELECTRIC CABLE voltage rating and name of manufacturer shall be embosed on the outersheath.
7. Fire resistant cables shall be selected in accordance with the following :
i) They shall be of 300 Volt/500 Volt grade to BS 6387 and suitable for 75 degree C conductor temperature.
ii) They shall have fire resistant characteristic to IEC 331 which are established by special mica fire proof tape applied over the conductor.
iii) Special fire retardant polyethylene is used for sheathing material of the cable. They shall have flame retardants characteristics to IEC 332-1.
iv) They shall have features such as non-toxis gas (non-halagon gas) and low smoke generation at fire to IEC 754-1.
v) Terminations, unless otherwise specified shall be rated for 105 degree C.
8. Busbar trunkings shall be selected in accordance with the following :-
i) They shall be of low resistance, totally enclosed, non-ventilated interchargeable feeder to plug-in type having current density not exceeding 1500 Amp. per 1000 mm2 and comply fully with BS 159.
ii) Unless otherwise specified, they shall withstand a minimum breaking capacity of 31 MVA at 415V, 50 Hz for a duration of 3.0 Second.
iii) Phase and neutral busbars shall have the same cross-sectional area. They shall carry continuous rated current with temperature rise not exceed 55 degree C. The impedance characteristic shall be such that the line to line voltage drop at rated current for any power factor will not exceed 0.115 volt per meter for feeder duct or 0.145 volt per meter for plug in duct.
iv) The trunking channels and removable cover plates shall be constructed to 14 gauge and 16 gauge galvanised mild steel sheet respectively and finished with two coats of approved paints.
v) They shall be supplied in sectional lengths to suit the installation. Proper expansion joints shall be provided at every 6 meter interval between the lengths. Continuous tinned-copper earthing strips of not less than 25% of cross-sectional area of phase conductor shall be provided between lenghts of busbar trunkings.
vi) Each section of the busbar trunking shall be removable without disturbing any section.
9. Wiring devices shall be selected in accordance with the following:-
i) They shall have voltage rating suitable for the supply characteristics to which they are applied.
ii) They shall be manufactured from moulded track-resisting material to BS 1322 and shall be of the type and rating as specified and shown in the Drawings.
iii) Unless otherwise specified, lighting switches shall be 5 Amp. rating, flush mounting, rocker operated type single pole, 2-way switch and comply with BS3676. They shall be grid switch type for multigang and plate switch type for single gang.
iv) All switches rated at 20 Amp. and above shall be of the double pole type, flush mounted and rocker operated incorporating pilot lamp.
v) Unless otherwise specified, lighting socket outlets shall be 5 Amp. rating flush mounting, shuttered, round pin type rocker operated with single-pole micro break switch and complying with BS 546.
vi) Unless otherwise specified, power socket outlets shall be 13 Amp. rating, flush mounting, shuttered, rectangular pin type, rocker operated with single-pole micro break switch and complying with BS 1363.
vii) In the electrical and mechanical equipment rooms, all switches and socket outlets shall be of the metalclad type.
viii) Where exposed to weather, socket outlets shall incorporate locking rings and rubber gaskets in the weatherproof housing manufactured for the purpose and provided with screw-in cover. Switches shall be of the type fitted with a cork gland around the stem of the operating knob and by a cork gasket between the cover and the base.
ix) Ceiling roses shall comply with BS 67. They shall be either surface or semi-recess type with the base having a minimum of three knockouts for cable entires. The base shall incorporate clamp type terminals suitable for holding the phase, neutral, earth and loop-in cables in a distinct manner. The cover plates shall be of the screw-in type.
x) 15A switched soclet outlets and socket outlets shall be of round pin type and comply
