SECTION 7:WIRING AND DISTRIBUIION ARRANGEMENTS
SECTION 7
WIRING AND DISTRIBUIION ARRANGEMENTS
700 WIRES AND CABLES
700-1 Every cable for use as fixed wiring shall be selected from one of the following types:
- 600/1000 Volts multi-core PVC insulated and PVC sheathed armoured and unarmoured cables.
- 600/1000 Volts multi-core XLPE insulated PVC sheathed armoured and unarmoured cables.
- 450/750 Volts single core PVC insulated cables.
- 450/750 Volts single core PVC insulated and sheathed cables.
- 450/750 Volts Twin core and earth PVC insulated and sheathed cables.
- 600/1000 Volts single core PVC or XLPE insulated and non-magnetic armoured cables.
- 600/1000 Volts mineral insulated cables.
- 600/1000 Volts multicore silicone rubber insulated hard grade PVC sheath bonded to coated aluminium fort cable with fire resistance and fire retardant properties.
- Other cables subject to the approval of Electricity Distribution Directorate.
All cables shall have conductors of plain annealed copper. The PVC insulation employed shall be suitable for the site conditions.
700-2 The maximum permissible drop in voltage from the consumer’s terminal to any point in his installation shall not exceed 2.5 % of the nominal voltage when the conductors are carrying full load current (6 volts for 1 phase and 10 volts for 3 phase systems).
700-3 Sizes of single core and multi-core cables shall be such that current carried by them shall not exceed those shown in the appropriate tables in Section 12.
700-4 Cables shall not generally be connected in parallel except where for a particular loading, a single cable is insufficient and it is not practical to employ bus bar trunking. In such situations single core or multicore cables may be connected in parallel provided that the cables are of the same type, size and length to ensure proper division of the current.
700-5 Identification of wires and cables
- Single core, PVC insulated, non-armoured cables used for wiring shall be identified by the following colours
Phase : Red / Yellow / Blue
Neutral : Black
Earth : Green/Yellow
- The conductors of multi-core PVC insulated and nonarmoured cables shall be identified by the following colours
Two-core cable : Red, Black
Three-core cable : Red, Yellow, Blue or Red, Black, Green/Yellow
Four-core cable : Red, Yellow, Blue and Black
- All wires or conductor to the neutral of the supply shall have "BLACK" outer layer of insulation and shall not be used as phase conductor. Similarly, Green/Yellow coloured wires or conductors of cables shall be used as "EARTH" conductor only.
700-6 All Conductors and cables shall be adequately protected against any risk of mechanical damage to which they may be liable in normal conditions of service.
700-7 Cables shall not be run in a life shaft unless they form a part of the lift installation. Cables of lift installations other than travelling cables in such a shaft shall be protected from mechanical damage and shall be armoured or mineral insulated cables or enclosed in metal conduits.
700-8 The different cables specified in Clause 700.1 shall be installed in the manner indicated below:
- Multi-core PVC or XLPE insulated armouredd and, PVC sheathed cables may be directly buried in the ground, laid in trenches and trays or drawn through ducts. The maximum current carried by any cable will depend upon the worst conditions of installation.
- Multi-core PVC or XLPE insulated, non-armoured and PVC sheathed cables may be installed in cable trays and in trenches or fixed to the walls by cleats. These cables shall only be installed at locations where they will not be damaged.
- Single core PVC insulated cables shall only be run in conduits or in trunking.
- Twin core and earth PVC insulated and PVC sheathed cables may be run on wooden battens fixed to the walls or may be installed within metallic partitions provided always that they are not liable to damage.
- Mineral insulated cables may be installed at locations where flame-proof installations are necessary or at locations of high temperature and elsewhere as required.
NOTE: The ends of mineral insulated metal sheathed cables shall be protected from moisture by being suitably sealed and the installation shall be thoroughly dry before the sealing material is applied. Such sealing material and any material used to insulate the conductors where they emerge from the insulation, shall have adequate insulating and moisture-proofing properties, and shall retain these properties throughout the range of temperatures to which the cables is subject in service.
- Multi-core silicone rubber insulated PVC sheath bonded to coated aluminium foil cable with fire resistant and retardant properties may be employed where flame proof installations are necessary, or at locations of high temperature or for emergency and fire alarms circuits and elsewhere as required.
- Single core PVC or XLPE insulated and non-armoured cables may be installed in cable trays, trenches and ducts or fitted to the walls by cleats. At all locations they shall be protected from damage.
- Single core PVC or XLPE insulated and non-magnetic armoured cables may be installed in cable trays, trenches and ducts or fitted to the walls by cleats. At all locations they shall be protected from mechanical damage.
705 FLEXIBLE CORDS AND CABLES
705-1 No size smaller than 16/0.2mm (0.5 mm² shall be used. Size of flexible cords and cables shall be such that the current normally carried by them shall not exceed the values shown in the appropriate table in Section 14.
705-2 Where apparatus requires to be earthed, flexible with earth core shall be used.
705-3 Flexible cords and cables shall be so connected to plugs or ceiling roses, etc., that the Brown or Black sheathed conductor is connected to the phase, the Blue sheathed conductor to the neutral and the Green/Yellow conductor to the earth.
705-4 Flexible cables and cords shall be so connected to portable or fixed apparatus, standard lamps, etc., that the green/yellow conductor is connected to the frame of the apparatus and any single pole switches are so connected that they break the phase conductor to the apparatus.
705-5 In all situations where flexible cables and cords are exposed to the risk of mechanical damage, they shall as a minimum be of a type sheathed with rubber or PVC and where necessary shall also be armoured.
705-6 Where flexible cables and cords are normally exposed to the risk of damage due to high temperatures, they shall be insulated with silicone rubber or other approved insulating materials.
705-7 Connections of flexible cords and cables to terminals of apparatus and accessories shall be made in a similar manner to those of cables.
705-8 The current carrying capacities of flexible cables and cords and the maximum weight that they may carry shall not exceed the values given in the appropriate table in Section 14.
705-9 All flexible cables and cords shall have the following identifications:
- Two core : Brown………………..Phase
Blue………………..…Neutral
- Three core : Brown or Black………Phase
B
Blue………………….Neutral
Green/'Yellow……..…Earth
- Four or Five core : Brown………………..Phase
Blue………………….Neutral
Green/Yellow…..…….Earth
705-10 Flexible cables and cords shall be used only for the following purposes
- As pendants
- As wiring of fixtures
- As connection of portable lamps or apparatus
- As lift travelling cables.
NOTE: In other special situation flexible cable may be employed after the prior approval of the EDD.
710 JOINTS, CONNECTIONS AND TERMINATIONS
710-1 Joints shall be avoided in conductors of all sizes wherever possible, and in final circuits feeding two or more lights, switches, sockets and/or other accessories, the loop-in system of wiring shall be employed.
710-2 Where joints are essential, they shall be housed in purpose made boxes and/or otherwise readily accessible for inspection throughout the life of the installation. Under no circumstances shall joints be drawn into conduits or positioned in the thickness of walls, ceiling or floor, etc., or behind plaster, tile or panel finishes etc.
710-3 Joints in cable conductors shall be mechanically and electrically sound and shall be made by soldering, brazing, welding or mechanical clamps or be of the compression type. All mechanical clamps and compression type sockets shall securely retain all the wires of the conductors.
710-4 Every joint in a cable shall be provided with insulation not less effective than that of the cable cores and shall be protected against moisture and against mechanical damage. Soldering fluxes which remain acidic or corrosive at the completion of the soldering operation shall not be used.
710-5 Joints in earth continuity conductors, earth leads, etc., shall be made in a similar manner to those in current carrying conductors.
710-6 Joints in flexible cables and cords shall not be permitted.
710-7 All terminations of cable conductors shall be mechanically and electrically sound and every termination shall be made by means of a terminal, soldering socket or compression type of socket. The termination arrangement shall contain and anchor all the wires of the conductor and shall not impose any serious mechanical strain on the terminal or socket.
710-8 At all terminations of cables, the insulation shall be neatly stripped without nicking the strands of the conductor. The conductor shall be tightly twisted and doubled backed (where space is available in the terminal) before being clamped with pinching screws. Where two or more sables are looped into the same terminal, their conductors shall be tightly twisted together before being inserted into the terminal. In no case shall bare conductor be allowed to project beyond any insulated shrouding or mounting of a live terminal.
710-9 At all terminations of wires and cables, sweating sockets or cable lugs shall be used unless adequate pinching screw terminals or clamps are provided and their use approved by the Engineer. In all such cases, the cable ends shall be tinned solid. Such lugs and sockets shall be connected in a manner that they are and with remain both mechanically and electrically sound and efficient. Only acid-free soldering fluxes shall be used. Any insulation and/or protective covering on the cables damaged by heat of the soldering shall be replaced by suitable and approved insulating sleeves.
715 BUNCHING AND SEGREGATION OF CONDUCTORS
715-1 Where conductors or bunches of conductors are protected by metallic sheathing, installed in metallic conduits trunking or ducts, the conductors of an phases and neutral, associated with any one circuit, shall be included in the same sheath, conduit, trunking or duct.
715-2 Where conductors pass through the metallic case of any switch, fuse, distribution board or other apparatus, or through any structural steel of any building, etc., an phase conductors and the neutral associated with any circuit shall pass through the same hole or aperture.
715-3 The dividing of the conductors of any circuit in such a manner that they induce magnetic fluxes or electrical currents in their sheathing or adjacent or surrounding metal of any sort shall not be permitted.
715-4 Where 230 volt loads are fed from a three phase and neutral distribution board no multi-gang switch or socket outlet box shag contain the wiring fed from more than one phase.
715-5 Not more than three lighting circuits or two socket circuits shall be bunched in the same conduit.
715-6 Where circuits are bunched proceeding from the distribution board and have separated they shall not be brought back again into any common conduit.
715-7 Circuits fed from distinct sources of supply different distribution boards or through separate isolators shall not be bunched in one conduit.
720 RIGID METALLIC CONDUITS
720-1 The use of rigid metallic conduits shall be permitted for general electrical installation provided that it is from heavy gauge steel and hot-dip galvanized inside and outside. Black enamelled steel conduits shall not be used for electrical installation. All metallic conduits shall be screwed typed.
720-2 The metallic conduit and its accessories shall form a continuous metallic sheath of adequate strength surrounding the cables throughout the length of the conduit.
720-3 Metallic conduits shall not be run under floor tiles of buildings.
720-4 The bores of all conduits shall be smooth and free from projections and/or edges which may injure the wires or prevent them being drawn in. The internal edges of the end of all lengths of conduit shall be reduced or chamferred before assembling into position.
720-5 All runs of conduit shall be assembled complete with all necessary accessories and the whole firmly attached to the structure of the building before any wires are drawn in. All wires shall be drawn through the covers of inspection and other fittings installed for the purpose.
720-6 All threads, vice marks, tool marks and breaks in the protective coating on metallic conduit and conduit fittings shall be painted with a steel preserving paint immediately after erect ion.
720-7 No run of conduit shall exceed 10 metres between adjacent draw-in points, nor shall contain more than two right angle bends, set or other deviation from the straight line.
720-8 Inspection couplings or long through draw-in boxes shall be used where necessary in straight runs of conduits for drawn-in purposes and shall be placed so that cables can be inspected and if necessary withdrawn throughout the life of installation.
720-9 Where conduit and/or conduit fittings are attached to switches, distribution boards, boxes or other equipment, smooth bore male brass bushes and flanged couplings shall be used.
720-10 Circular or hexagonal heavy locknuts shall be used at all positions where running joints are required and great care shall be taken to see that they seat firmly and evenly into mating faces of couplings or other adjacent accessories.
720-11 Where exposed to water, rain or weather, all covers shall be arranged or fitted with machined joints and/or fitted with durable gaskets such that water cannot get inside
720-12 All runs of conduits shall be truly vertical or horizontal except where the architectural features of the building demand otherwise.
720-13 Except where provision is made for fastening a box or other conduit fitting directly to the structure of the buildings and such fastening is made, conduit shall be saddled to the structure of the building within 15 cms. of each terminal box, angle box, bend or other conduit fitting and at intervals not greater than 1.5 m. Couplings and through type drawing boxes shall be counted as part of a straight run of conduit.
720-14 All boxes, bends and other accessories shall be of the same material as the conduit and shall have the same protective coatings. Grey cast iron boxes etc. may be used with metallic conduit, but shall be finished in the same manner as the conduit to which they are directly attached.
720-15 The number of single core PVC insulated non-sheathed cables run in metallic conduit shall be such as to permit easy drawing of the cables. The actual number of cables drawn into any conduit shall not be greater than the number given in the appropriate table in Section 14. Where different sizes of cables are drawn into a conduit, the number and sizes of cables installed shall be selected in accordance with the method detailed in Section 14.
720-16 Metallic conduits system must be provided with a separate insulated earth wire and the conduit itself may not be considered as the earthing system. All joints shall be made mechanically and electrically continuous.
720-17 The minimum size of metallic conduit that may be used in electrical installations shall be 16 mm diameter. Other sizes of conduits shall be limited to the following diameters 20 mm, 25 mm, 32 nun, 38 mm and 50 mm.
725 RIGID NON-METALLIC CONDUITS
725-1 Rigid non-metallic conduits may be employed in general electrical installations provided it is made from polyvinyl chloride or equivalent material that bas been certified as suitable for use at ambient temperatures upto 55°C. Additionally the material shall not soften or suffer any structural degradation at a temperature of 85°C, shall be non-hygroscopic, and self-extinguishing type.
NOTE: Rigid non-metallic conduits shall not be used at locations where they will be subjected to mechanical damage.
725-2 The inside and out side surfaces of non-metallic conduits shall be smooth and fresh from burrs and similar defects. The interior and ends of conduit fittings shall have no sharp edges and corners, shall be smooth and well rounded to permit easy drawing in of cable and prevent any damages to cable insulation.
725-3 The entries of non-metallic conduit fittings shall be so designed that are liable water tight joint can be made between the conduit and fittings. Vinyl cement shall be used to make all joints. A vinyl solvent shall be used for permanent joints and a cement of the type that shall continue to remain in a sticky condition shall be used for expansion couplers.
725-4 Rigid non-metallic conduits shall be so constructed that it will be possible to bend the conduit easily with the aid of bending spring and all conduits and conduit fittings shall be of the unthreaded type.
725-5 The minimum size of rigid non-metallic conduit used for general electrical installation shall be 16 mm diameter. Other sizes of rigid non-metallic conduits shall be of the following diameters
20mm, 25mm, 32mm, 38mm and 50mm
725-6 The number of single core PVC insulated non-sheathed cables run in one conduit shall be such that it permits easy drawing of the cables. The actual number of cables drawn into any conduit shall not be greater than the number given in the appropriate table in Section 14. Where different sizes of cables are drawn into a conduit, the number and sizes of cables installed shall be selected in accordance with the method detailed in Section 14.
NOTE: Where a number of cables are bunched in one conduit, the current carrying capacity of the cables shall be reduced by using the stipulated grouping factor. For full details, refer to section 14.
725-7 A separate insulated earth wire shall be drawn into all rigid non-metallic conduits.
725-8 Rigid non-metallic conduits shall be installed generally in accordance with the requirements set out for metallic conduits. Additionally the method of supporting rigid non-metallic conduit shall allow for the longitudinal expansion and contraction of the conduits.
725-9 Where a lighting fittings is suspended from a non-metallic conduit box, care shall be taken to ensure that the temperature of the box does not exceed the permitted safe temperature of the material and is fitted with screwed metal insert clips. The mass suspended from the box shall not exceed 2 kgs.
730 CABLE TRAYS
730-1 Cable trays may be employed in warehouses and other industrial buildings for supporting cables. In residential and commercial buildings cable trays may be employed in mechanical equipment and plant rooms. Where service floors or similar facilities are available cable trays may be employed at other locations in commercial and residential buildings also.
730-2 Cable tray system shall comprise of a unit or assembly of units or sections, and associated fittings, made of metal or other non-combustible materials forming a rigid structural system. Cable tray systems include ladders, troughs, channels and solid bottom trays.
730-3 Multi-core armoured or non-armoured cables may be supported by cable trays. Single core insulated and sheathed cables may also be installed in cable trays.
730-4 Cable trays shall not be used in lift shafts or at locations where they will be subjected to severe physical damage.
730-5 Cable trays shall have adequate strength and rigidity to provide satisfactory support for the cables contained within it. All sharp edges, burrs and projections shall be removed and the tray shall be finished smooth to prevent injury to cables.
730-6 Metallic cable trays shall be adequately protected against corrosion by galvanishing or shall be made of corrosion resistant material.
730-7 Non-metallic cable trays shall be made from polyvinyl-chloride or equivalent and shall be fully suitable for continuous service in the climatic conditions of Bahrain.
Note: PVC used in cable trays shall comply with the requirements of Clause 725.
730-8 All cable trays shall be equipped with sides of adequate dimensions. All fittings bends, tees, employed shall be completed before the installation of cables.
730-9 Cable trays shall be installed as complete system with bends and other accessories. Each run of cable tray shall be completed before the installation of cables.
730-10 Adequate supports shall be provided to prevent stress on cables where they enter or leave the tray. Where cable trays extend transversely through partitions and walls additional protection in the form of non-combustible covers shall be used.
730-11 Sufficient space shall be provided and maintained around cable trays to permit adequate access for installing and maintaining the cables.
730-12 The number of multi-core cables that may, be installed in a ventilated or solid bottom cable tray shall not be greater than the number given in the appropriate table in Section 14.
Note: Where a number of cables are installed in a cable tray the current carrying capacity of the cables shall be reduced by using the stipulated grouping factor. For full details, refer to Section 14.
730-13 Metallic cable trays shall not be used as an earth continuity conductor.
735 CABLE TRUNKING
735-1 Cable trunking may be employed for housing single core cables at special location where it is difficult to install conduits. They may be of metallic or non-metallic construction. Non-metallic cable trunking shall be constructed from non-combustible insulating material like polyvinyl-chloride which shall be fully suitable for use in the climatic conditions and shall comply with the requirements of Clause 725. Metallic cable trunking shall be adequately protected against corrosion by galvanising or shall be made of corrosion resistant material or stove enamelled. All cable trunking shall be provided with removable covers.
735-2 Cable trunking shall generally be run exposed and the trunking shall be completely erected before drawing in the cables. Where adequate means of access is readily available throughout its length, cable trunking may be concealed.
735-3 Every entry to trunking shall be so placed as to prevent the ingress of water and all deadends shall be closed. Only unbroken lengths of trunking shall be employed for crossing positions and walls.
735-4 Where a common cable trunking is employed for housing both power and communication circuits, or for housing circuits operating at different voltages, the trunking shall be provided with separate compartments for the different types of circuits.
735-5 Cable trunking shall be manufactured from substantial sections to provide adequate strength and rigidity. AR sharp edges, burrs and other projections shall be removed and the trunking finished smooth to prevent injury to cables.
735-6 All bends, tees and other accessories of cable trunking shall be substantial sections and of the same quality as the trunking itself.
Note: Where a number of cables are bunched in trunking the current carrying capacity of the cables shall be reduced by using the stipulated grouping factor. For full details, refer to Section 14.
735-7 Cable trunking shall be securely supported every metre, when run exposed.
735-8 The number of single core cables that may be housed in a trunking shall be such that a space factor of 45 percent is not exceed or shall be selected in accordance with the method detailed in Section 14.
735-9 Metallic trunking shall be provided with a separate insulated earth wire. The trunking itself may not be considered as the earthing system. All joints shall be made mechanically and electrically continuous. The different sections of the trunking shall be bonded by copper links.
735-10 Non-metallic trunking shall be provided with an insulated earth wire for each circuit.
740 FLEXIBLE CONDUITS
740-1 Flexible conduits may be employed for connecting electric motors and other equipment subject to adjustment of position and vibration to the fixed wiring and at similar positions.
740-2 Flexible conduits may be of the metallic or non-metallic type. Flexible conduits shall not be used as the sole means of providing earth continuity and in both type of flexible conduit separate earth continuity conductor of appropriate size shall be provided.
740-3 In damp and wet locations all flexible conduits shall be of the type that prevent the ingress of water and moisture.
740-4 Flexible conduits shall be run exposed and shall be so positioned that they are not susceptible to mechanical damage. Where necessary flexible conduits shall be adequately supported.
745 BUS BAR TRUNKING
745-1 Busbar trunking may be employed as horizontal feeders from mains switch board to submain switch boards and as risers to the different floor distribution boards. The bus bars shall be totally enclosed in metallic housing of substantial construction and of adequate strength to withstand the electro-mechanical forces that may be induced by the prospective short circuit current.
745-2 All bus bar trunking shall be so designed and arranged that they are free to expand and contract without detriment to themselves or to adjacent parts of the installation. All dead ends of bus bar trunking shall be closed. Fire barriers shall be provided at each floor level.
745-3 All bus bar trunking shall be surface mounted and so installed that they are inaccessible to unauthorised persons. They shall be securely supported and only unbroken lengths shall be permitted at floor crossings. Bus bar trunking shall not be installed in lift shafts.
745-4 No branch connections shall be permitted except through tap off units. Tap off units shall incorporate the required excess current protective devices.
Note: Clause 5O7 allows omission of excess current protection if floor distribution board is in the same room.
745-5 All bus bars employed in bus bar trunking shall be of high conductivity copper supported on adequately rated and sized insulators.
750 FINAL CIRCUITS
750-1 Each final circuit shall be connected to a separate way of a distribution board, a consumer service unit or a splitter switch.
750-2 The wiring of each final circuit shall be electrically separate from that of every other final circuit and each circuit shall be provide with its own separate neutral.
EXCEPTION: In ware-houses, factories, workshops, hangars and other larger areas where it is desirable to connect adjacent lights to different phase of the supply, it is permissible to employ a three phase and neutral circuit comprising of 4-wires as a final circuit provided the circuit is controlled by at triple pole breaker in the distribution board.
750-3 Final circuit having a rating exceeding l5/16 amperes shall not supply more than one point.
EXCEPTION:
- 13 ampere socket outlets connected to a radial or a ring circuit as per Clause750.10 and 750.11.
- Two or more 30/32 ampere socket outlets feeding portable x-ray or welding equipment etc., may be connected to one final circuit and protected by a maximum 30/32 ampere fuse or circuit breaker provided it is ascertained that the maximum load on the circuit will not exceed 30/32 ampere and the circuit wiring is rated as minimum for this current.
- Two or more 60/63 ampere socket outlets feeding portable x-ray or welding equipment, etc., may be connected to one final circuit and protected by a maximum 60/63 ampere fuse or circuit breaker provided it is confirmed that the maximum demand on the circuit will not exceed 60/63 amperes and the circuit wiring is rated as minimum for this rating.
- A cooker control unit incorporating a socket outlet or a lighting track system in which individual luminaries are suitably protected against excess current.
750-4 No cable with a conductor smaller than 1.5 mm² shall be used as a final circuit.
750-5 A l.5 mm² cable may be employed as a final circuit for supplying lighting points and protected by a fuse or circuit breaker of 10 amps rating providing the circuit loading is limited to 2000 VA.
Note: Circuits for discharge lamps including fluorescent lamps shall be designed to carry total steady current viz, that of the lamp and any associated control gear and also their harmonic current. Where more exact information is not available, the demand in voltamperes may be taken for the purpose of this regulation as the rated lamp watts multiplied by no less than 1.8. This multiplier is based on the assumption that the circuit is corrected to a power factor of 0.85 lagging as required per Clause 313 and also takes into account control gear losses and harmonic current.
750-6 Cables with conductor of 2.5 mm² or greater may also be employed for supplying points where large distances or high wattage fittings are involved.
750-7 Two socket outlets of 13 amps rating may be connected to a single phase and neutral circuit wired with 2.5 mm² cable, protected by a fuse or circuit breaker of rating not exceeding 15/16 amps.
750-8 One socket outlets of 15/16 amps rating may be connected to a single phase and neutral circuit wired with 2.5 mm² cable, protected by a fuse or circuit breaker of rating not exceeding 15/16 amps.
750-9 Six socket outlets of 13 amps rating may be connected to a single phase and neutral circuit wired with 2.5 mm² cable, protected by a fuse or circuit breaker of rating not exceeding 15/16 amps, serving one room only of less than 50 sq. metres floor area which is not a kitchen, provided that no fixed water heater or window air conditioning unit shall be connected to any of those points.
750-10 Six socket outlets of 13 amps, rating may be connected to a single phase and neutral circuit wired with 4 mm² cable, protected by a circuit breaker of rating not exceeding 25 amps, provided that the total connected load of the circuit does not exceed 5 KVA.
750-11 Ten socket outlets of 13 amps rating may be connected to a single phase and neutral ring circuit subject to the following provisions.
- The circuit shall consist of a ring of 2.5 mm² cable looped from one socket to the next throughout the circuit and from the last socket back to the distribution board. Except in the case of the sockets connected on a spur as indicated in a sub-clause 5, not more than two conductors shall be connected into one terminal of any socket. No joints shall be permited in any box housing a socket.
- The circuit shall be protected by a fuse or circuit breaker of rating not exceeding 30/32 Amps.
- Ring circuit shall not be used where there is any likelihood of the total connected load of the circuit exceeding 7 KVA.
- In special situations not more than two sockets may be connected as spur from the ring.
- A diagram illustrating the ring circuit appear as an appendix to this Regulations.
750-12 All wire sizes indicated in sub-clause 750.4 to 750.11 inclusive, relate to PVC insulated cables run as single circuits viz., without assuming any grouping factor. Where mineral insulated cables or cables with other insulating materials are employed for final circuits, the wire sizes stipulated in the above sub-clauses may be appropriately reduced and wire sizes having the same current rating as those specified for PVC insulated cables may be employed.
750-13 Where two, socket outlets are housed in one common box, this will be considered as one outlet only for purposes of interpreting sub-clauses 750.7 to 750.11 both inclusive.
750-14 All single phase socket outlets in any one room shall normally be connected to the same phase of the supply. In larger rooms and other areas, socket outlets connected to any one phase are grouped together and no two socket outlets connected to different phases of the supply are less than 2 metres apart.
EXCEPTION: Where an under-floor ducting system is employed the minimum distance between any two outlets to different phases of the supply may be further reduced to 1.2 metres.
750-15 Fixed window type air conditioning units, and other fixed equipment like water heaters, shall be connected to the circuit only by means of a switch, fuse or circuit breaker.
750-16 A shaver outlet provided with a double wound isolating transformer may be connected to a lighting circuit.
750-17 For all other final circuits the size of cable employed shall be suitable for the load connected and no diversity shall be allowed . Section 14 provides a detailed method of selecting circuit sizes and the excess current protective device to be employed, which shall be adhered to for all circuits.
755 WIRING ACCESSORIES - LOCAL SWITCHES
755-1 All local switches shall be of adequate capacity. For outdoor use switches shall be water-tight and metal-clad, Switches not designed to break an inductive load of its full rated capacity if used to control discharge lighting circuits shall have a current rating of not less than twice the total steady current which it is required to carry.
755-2 Normally all local switches shall be mounted with the dolies between 1.0 m and 1.5 m above the finished floor level. Where several switches are mounted in two or more horizontal rows, the lowest row shall have dollies at least. 1.0 m above the finished floor level. Unless prevented by the swing of the door, all switches shall be mounted inside the room on the side of the door where the catch or lock is situated the nearest switches being approximately 15 cms. from the door frame. The switch nearest the door shall control one or more of the principal lights of the room. In large rooms where groups of switches are employed the switching arrangement shall be carried out in a symmetrical manner.
755-3 In kitchens and other situations excepting bath rooms, where water is regularly used, no switch shall be mounted within two metres of any tap, basin, sink or metal drainage board.
755-4 In bath rooms all switches shall be of the ceiling mounted cord operated type if located inside. Otherwise, switches shall be located in an accessible position outside the bath room and immediately adjacent to the door.
755-5 All one way switches both single and double pole shall be so mounted that the dolly is up when the switch is in the "OFF" position. All single pole switches shall be so connected that they control the phase lead to the light or other consuming device.
760 WIRING ACCESSORIES - SOCKER OUTLETS AND PLUGS
760-1 Socket outlets shall be of the 13 Amps, 3 pin type or 15/16 amps, 3 pin round pin type with shuttered line sockets. The earth contacts of each socket shall be effectively connected to the earth continuity conductor and the phase and neutral shall be connected to the correct sockets. When viewed from the front in its final mounted position, earth socket shall be at the top, the neutral socket shall be below to the left and the phase socket shall below to the right.
760-2 No socket outlets shall be mounted in any bath room except for shaver socket outlet.
760-3 No socket outlet shall be mounted within two metres of any tap sink, basin in any kitchen, clockroom, etc., without the special approval of the Engineer in each case. Except where otherwise specified, all socket outlets shall be mounted 30 cm above the floor or work bench where bench apparatus specified will be used. Socket outlets shall not be mounted at locations where they are liable to come into physical contact with fabrics or other material that may catch fire due to transmission of heat.
760-4 Socket outlets and plugs for use on more than one phase shall include a pin or other approved contact for the earth continuity connection which shall make contact before and break contact after all the phase connections and the neutral connections where such is fitted.
Where a pin for the neutral conductor is fitted it shall make contact not later than and break contact not earlier than all the pins for the phase conductors. The design of the socket and plug shall be such that the plug cannot be inserted in such a manner that the neutral and any phase conductors become wrongly connected to the supply.
760-5 All 3 phase socket outlets shall be combined with switch so interlocked with the plug that the plug cannot be withdrawn or inserted with the switch in the "ON" position.
765 WIRING ACCESSORIIES-JUNCTION BOXES AND FUSED SPUR BOXES
765-1 Junction boxes shall be complete with a terminal block suitable for connecting up to 10 mm 3 core copper conductor cables and an all-insulated moulded cover plate. The cover plate shall permit easy connection of outgoing cable.
765-2 Fused spur-box shall be unswitched type equipped with fuse base and carrier and 13 amps, fuse link fully shrouded to permit safe replacement of fuse. The terminal shall accommodate 3 core, 4 mm² copper conductor cables.
770 WIRING ACCESSORIES - LAMP HOLDERS
770-1 All lamp holders shall preferably be of the all-insulated pattern and if not separately and firmly attached to a bracket, conduit or block shall have a substantial cord grip with the flexible wire so connected that no pull due to the weight of the holder, lamp shade or fitting or pull on the flexible can be transmitted to the connections of the conductors to the terminals.
770-2 All batten, back-plate or thread mounted lamp holder shall be free from edges or other projections which might damage the wiring.
770-3 In bath room, kitchen and other places where water is regularly used, no lamp holder less than 2.5 metres from the floor shall be within 2 metres of any taps, bath, basin or sink, unless it and the lamp are totally enclosed in. a fitting of all insulated construction and the lamp-holder is of the heavy duty porcelain type. Such fitting shall not be of the type which is suspended by the flexible cord, but shall be permanently mounted on the wall or otherwise supported independently of the current carrying conductors.
770-4 All lamp-holders of the screw cap lamps shall be so connected that the contact formed by the screw cap is connected to the neutral conductor.
775 WIRING ACCESSORIES - CEILING ROSES
775-1 All flexible cords and cables not connected to the supply by plug and socket shall be connected by means of insulated ceiling roses. Where the flexible cord or cable contains an earth continuity conductor, the ceiling rose shall be of the three or four plate type with the following terminals
For three plate : Two + Earth (Phase, Neutral and Earth)
For four plate: Two + Loop-in + Earth (Phase, loop-in, neutral and Earth)
The terminals shall be clearly marked for identification by letters stamped or cast into material of which the ceiling rose is made.
775-2 Ceiling roses shall be securely fixed to the structure of the building and shall not hang on or strain any wires feeding them. Flexible shall be securely anchored so that no pull from them can be transmitted to the conductor connections.
775-3 Where flexible cables supplying water heaters or other fixed apparatus are too large to be connected by a ceiling rose, a suitable heavy duty junction box may be used instead. In all cases the flexible cable shall be so arranged and secured that any pull on the cable shall be transmitted directly to the structure of the box and not to any current carrying or earth continuity connections.
780 WIRING ACCESSORIES - MOUNTING BLOCKS & BOXES
780-1 Where conduits are run on the surface of walls of the building, all branch switches, sockets, ceiling roses, etc., shall be mounted on purpose made galvanized, P.V.C. or equivalent boxes specially designed for surface installation. All such boxes shall be securely fixed to the structure of the building in such a manner that they cannot rotate or rock throughout the life of the installation.
780-2 Where conduits are run buried in walls of the building, all branch switches, sockets, ceiling roses, etc., shall be housed in purpose made galvanised, PVC or equivalent boxes and all switch plates, socket plates and accessories shall be installed flush with the plaster.
785 SWITCHES AND ISOLATORS
785-1 All switches and isolators shall be of the load break type, of adequate size and robust construction. They shall be completely enclosed in a heavy gauge rust-proofed sheet steel or all insulated housing with the cover interlocked with the operating handle in such a manner that the cover cannot be opened whilst the switch is in the 'ON' position.
785-2 Double pole switches shall break phase and, neutral conductors simultaneously. Switches controlling more than one phase shall not break the neutral conductor but shall break all phases simultaneously
EXCEPTION: 4 pole c.o.e.l.c.b's used as isolators in distribution boards may break the neutral conductor also.
785-3 Where fuses are also incorporated within the same housing as the switch, the fuses shall be so connected that the fuses are not alive when the switch is in the ‘OFF’ position. No fuse shall be inserted in the neutral conductor.
785-4 No switch shall be mounted in such a position that it can be touched by any person at the same time as any water taps, basins, sinks, metal drainage boards etc. The minimum clearance from any of the above plumbing fitting shall be two metres. Switches shall not be installed in any room containing a bath or shower bath or shower unless they are of the cord operated ceiling type.
790 DISTRIBUTION BOARDS
790-1 Distribution boards shall be housed in purpose made heavy gauge, rust-proofed sheet steel housing. The distribution boards shall be so installed that its top does not exceed 185 cms from finished floor level. Alternatively they may be housed in non-metallic enclosures provided the material employed is fully suitable for use in the climatic conditions and has the required insulation level.
790-2 Distribution boards having fuses or circuit breakers in the phase lead only shall not be controlled by any other switch having a fuse or circuit breaker in the neutral lead.
790-3 Each distribution board shall have a circuit schedule pasted or otherwise permanently fixed inside the cover or adjacent to the board stating what each way controls and the size or rating of the fuse or circuit breakers to be used. All such schedules shall be in both Arabic and English.
790-4 Where multi-phase circuits are connected to a distribution board, the corresponding fuse or circuit breaker in each phase shall control the same circuit.
790-5 Each phase of every distribution board shall have an adequate busbar of high conductivity electrolytic copper to distribute the electricity to the various circuit fuses or circuit breaker. Such busbar shall be provided with an adequate terminal or clamp to take the incoming main conductor.
795 UNDERFLOOR DUCTS
795-1 The installation of underfloor ducts shall be permitted beneath the surface of concrete or other flooring material.
795-2 Under floor ducts shall not be installed at locations which are regularly washed or where they are subject to corrosive vapours. In hazardous locations under floor ducts shall not be employed.
795-3 Unless adequate protection against corrosion is provided, metal underfloor ducts, junction boxes and fittings shall not be installed in concrete. Metallic and non-metallic underfloor ducts shall be of substantial construction.
795-4 All underfloor ducts shall be laid in straight lines and junction boxes shall be installed at all changes in direction. All junction boxes shall be levelled to the floor. Dead ends of all ducts shall be closed.
795-5 Underfloor ducts shall be provided with tap off position for outlets at regular spacing.
795-6 Throughout the underfloor duct system joints in conductors shall not be employed.
795-7 The combined cross sectional area of all conductors installed within the duct shall not exceed 40 percent of the interior cross sectional area of the duct or the duct size shall be selected in accordance with the method detailed in Section 14.
795-8 Where underfloor ducts serve more than one service as telephones, intercoms, etc. in addition to socket outlets, multi-sectioned ducts shall be provided and each service shall be housed in a separate duct. Outlet boxes serving-different services and installed within the same box shall be provided with suitable separators.
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