Wiring Materials And Installation Methods in Electrical Construction Works





Electrical wiring needs expertise attention to every building projects. It directly related to the safety of human beings and utilities / equipments people handle. The scope of electrical wiring shall cover supply, installation, testing and commissioning of all conduits and accessories, wiring, switches, socket outlets, junction boxes / pull boxes, GI pull wires, ceiling roses making connections etc. Unless otherwise indicated wiring shall consist of PVC insulated copper conductor wires installed in heavy gauge steel galvanized conduits.

1. Conduits

1.1 Galvanized Steel Conduits and fitting

Electrical Metallic Tubing (EMT) for electrical wiring

 

  1. Conduit Type: In general interior and exterior wires ways shall be Electrical Metallic Tubing (EMT).  Conduits shall conform to all provision of Underwriters laboratories UL 797, American National Standard Institute c80-3, Federal Specification WWC-563A and National Electrical Code Article 384.  The conduit shall be straight, have a circular cross section sufficiently accurate to accept approved couplings and fittings.  Wall thickness shall be uniform through and welding of seams shall be continuous and thoroughly done.  The interior surface shall be free from injurious defects.
  2. Number of conductors in tubing: The numbers of conductors in a single tubing shall not exceed the percentage fill specified in the NEC.
  3. Coupling Connector, Bends: Coupling and connector used with tubing shall be made up tight.  Bends in the tubing shall be so made that the tubing will not be injured and that the internal diameter of the tubing will not be effectively reduced.

1.2 Rigid and Flexible PVC Conduit

Rigid PVC Conduit for electrical wiring installation

  1. Conduit Type: PVC conduit shall be of the grey / black, round, heavy gauge, polyvinyl chloride (PVC) conduit conforming BS 4607 Part I, 1970 with compatible galvanized boxes.  The conduits internal surface shall be smooth.  All flexible steel conduits shall conform to 4607. The PVC conduit and fittings such as bends lock units, reducers, coupler check nuts, bushes etc. shall conform to BS 4607. Unless otherwise specified minimum size of conduits shall be 20 mm diameter. The conduits shall be suitable to use in an ambient temperature of 60 degree centigrade and shall not be installed in areas that receive direct sun light.  Ready Made bends shall be used.
  2. Number of conductors in tubing: The number of conductors in a single tubing shall not exceed the percentage fill specified in the NEC code.
  3. Coupling Connector, Bends: Coupling and connector used with tubing shall be made up tight.  Bends in the tubing shall be so made that the tubing will not be injured and that the internal diameter of the tubing will not be effectively reduced.

2. Wires, Cables And Cords

1. Wires: Unless otherwise specified all wires shall be PVC insulated single core, stranded copper conductor conforming to BS 6004. All wires shall be colored as follows:

    1. Phase A of 1: Red Color of wire
    2. Phase B of 2: Yellow Color of wire
    3. Phase C of 3: Blue Color of wire
    4. Neutral: Black
    5. Ground: Yellow Green or Green (One color only to be used for the complete Installation).

The size of wires shall be as indicated in the drawings.

2. Telephone Cables: The telephone cable used for telephone socket outlet shall be twin pairs 22 AWG, PVC insulated copper conductor wires, UL approved. The telephone cables used as main feeder connecting the telephone junction boxes to main telephone junction boxes shall be multi-pairs type, as specified on drawings.

3. Flexible Cords: The cords to connect short extension to the luminaries, immersion heaters, equipment etc. shall be heat resisting PVC insulated to BS 6500 - 1969 with copper conductors.

3. Wiring Accessories

1. Unless otherwise specified all wiring accessories shall be Standard British type.  The exact type & model shall be as specified in the drawings, bill of quantities or herein in the specific.

2. Outlet, Pull box, Junction Boxes and Fittings.

Each outlet, junction or pull box shall be of proper type, class and construction to suit the specific conditions encountered.  Outlet pull box or junction boxes shall be conforming with IEE regulations and other applicable requirements that have been established by the various agencies, codes and authorities.

Outlet, pull and junction boxes in general, be as follows:

2.1 Outlets for light points, convenient socket outlets, power outlets, switch boxes, pull / junction boxes shall be code gauge 46 mm deep galvanized steel, and shall be of shapes and size to suit their respective locations and installations and shall be provided with covers to suit their function and installation.

2.2 Outlet boxes shall be equipped with fixtures or straps where required.  All outlet boxes shall be provided with brass ground terminals.

2.3 All junction boxes/pull boxes shall have suitable covers.

2.4 Surface mounted outlet and junction boxes in the outdoor locations shall be of cast iron metal with threaded hubs.

2.5 The surface mounted indoor boxes shall be sheet steel painted purpose made for surface installation.

3. Lighting switches

For internal use shall be of the grid assembly pattern with rocker operated switch units suitable for operation with inductive loads.  Switches shall be either, one way, two way or intermediate as indicated in the drawings and shall be rated 20 Amps.

Switch plates shall be champagne, charcoal or satin chrome cover finish, MK make Accent type for all offices area.

Switch plates shall be Matt chrome cover finish, MK make ALBANY range for all services area, including toilets, kitchen, guard room, pump room, electric room etc. and metal clad cover finish shall be used in the factory, storage area, finished product, etc. where Electrical Metal Tube (EMT) pipes are used, as shown and described on drawings.

For internal surface installation switches shall be provided with matching steel box and shall be with metal clad finish.

External outdoor switches shall be covered with weather proof flap.  EGA tube make.

Pull cord switches shall be of white molded plastic suitable for surface mounted and shall be supplied with matching patterns.  These shall be manufactured by MK Co. Ltd. (England) or approved equivalent.

4. Convenient Socket Outlets

For flush indoor installation shall be 13 A, 3 pin switched socket outlet with indicator and manufactured to British Standard.  Finishing to be Matt chrome cover finish, MK make ALBANY range for all services area, including toilets, kitchen, guard room, pump room, electric room etc. and metal clad cover finish shall be used in the factory, storage, finished product, etc. where Electrical Metal Tube (EMT) pipes are used, as shown and described on drawings.

5. Telephone Outlets

Telephone outlets shall be suitable for surface or flush installation with American standard socket outlet.  The finish of the switch plates shall be Matt chrome cover finish, MK make ALBANY range for all services area, including toilets, kitchen, guard room, pump room, electric room etc. and metal clad cover finish shall be used in the factory, storage area, finished product, etc. where Electrical Metal Tube (EMT) pipes are used, as shown and described on drawings.

6. Spur Units

Spur units shall be 20A or 45A, DP switch type with pilot lamp. For flush installation shall be switched and fitted with neon indicator and cord outlet on the front plate.  Finish to be as specified elsewhere.

7. DP switch Outlet

The DP switch outlet shall be suitable for flush or surface type of installation.  The capacity as indicated on the drawings.  The finish shall be Matt chrome cover finish, Mk make ALBANY range for all services area, including toilets, kitchen, guard room, pump room, electric room etc. and metal clad cover finish shall be used in the factory, storage area, finished products, etc. where Electrical metal Tube (EMT) pipes are used, as shown and described on drawings.

8. Connector Outlets

Connector outlets shall comprise flush overlapping plates of white molded plastic suitable for attachment to standard recessed steel boxes.  These shall be fitted in three terminals a clamping device for outgoing flexible cable.

4. Wiring Installation

The wiring installation shall be in conformity with IEE regulation and/or approved equivalent standard.

Unless otherwise specified all wiring shall be in rigid PVC conduit embedded in wall, or ceiling or concealed in the false ceiling.

The size of conduits shall be selected in accordance with the IEE regulations and the minimum size of the conduit shall be 20 mm dia unless otherwise indicated or approved.

Factory made conduit bends shall be used where required.  Conduits shall be kept at minimum of 100 mm from the pipes of other non-electrical services.

Separate conduits and runways shall be used for:

1.    Lighting system.

2.    Power outlets.

3.    Emergency light.

4.    Telephone system.

5.    Fire alarm system.

6.    Sound / public address system.

7.    Television system.

8.    Computer system.

Wiring for short extensions to outlets in hung ceiling or to equipment, motors etc. shall be installed in flexible conduits.  Otherwise rigid conduits shall be used.

Conduits run on surfaces shall be supported on galvanized / PVC saddles which in turn are properly screwed to the wall or ceiling.  Saddles shall be at intervals of not more than 60 cm.  Fixing screws shall be with round cheese head or and rustproof materials.  Exposed conduits shall be neatly run parallel or at right angles to the wall of the building.  Pull boxes must be provided at the right angles and at a distance of not exceeding 20 meter length.

Conduits embedded into the walls shall be fixed by means of staples at not more than 60 cm intervals.  Chase in the wall shall be neatly made and refilled after laying the conduit and brought to the finish of the wall.

Conduits buried in concrete structure shall be put in position and securely fastened to the reinforcement and got approved by the consultant before the concrete is poured.  Proper care shall be taken to ensure that the conduits and boxes are neither dislocated nor choked at the time of pouring the concrete.

Suitable fish wires shall be drawn in all conduits before they are embedded.

Inspection boxes shall be provided for periodical inspection to facilitate draw and removal of cables.  Such inspection boxes shall be flush with the wall in the case of recessed conduits.

Inspection boxes shall be spaced at not more than 12 meters apart or two 90 degree solid bends or equal.

Use of PVC conduits in places where ambient temperature is 60 degree c or above is prohibited.  PVC conduits shall not be used in outdoor system.  Conduits shall be free from sharp edges and burrs and grease or oil shall not be used for the purpose of pulling the wire.  The entire system of conduits must be completely installed and rendered electrically continuous before the conductors are pulled in.

All PVC conduits shall be jointed with plain PVC couples using approved PVC jointing materials as recommended by the manufacturer.  All joints shall be water tight.  Junction between conduit and adaptable boxes, back outlet boxes, switch outlet boxes and the like must be provided with entry spouts and smooth PVC bushes.

A ground wire of not less than 2.5 sq. mm copper shall be run inside each conduit.  The wire shall be insulated and color coded.

5.  Branch Circuit wiring

All final branch circuits for lighting and appliances, shall be single conductor cables run inside conduits.

Branch circuit conductor sizes shall be as shown in the schedule of quantities and drawing and conforming the requirements of the IEE regulations.

Home runs indicated in the drawings for the final branch circuits shall be kept in a separate conduit upto the panel board via switches wherever called for.  No other wiring shall be bunched in the same conduit.

Flexible cords for connection to appliances, fans and pendants shall be 250/440V grade, three or four cores, with tinned stranded copper wires, insulated, twisted and sheathed with strengthening cord.  Color of sheath shall be subject to the architect approval.

For each lot of wires the contractor shall supply a certificate issued by the manufacturer stating its origin, date of manufacture, constitution and standard to which it complies and the test certificates.

Looping system of wiring shall be used.  Wires shall not be jointed.  Where joints are unavoidable, these shall be made through approved mechanical connector.

6. Control Switches

Control switches shall be connected in the phase conductors only and shall be ‘ON’ when knob is down.  Switches shall be fixed in galvanized steel boxes.  Chromium plated screws shall be used.

220 V (230 V) power supply wiring shall be distinctly separate form any other different voltage system and lighting wiring.

Though the circuit wiring is indicated on the drawing, contractor shall check and be responsible for the connection.

Each circuit phase wire from the distribution boards should be followed with a separate neutral wire of the same size as the circuit wire.

Each light point and outlet shall be identified with their circuit number and panel board number with a label pasted on them.

7. Testing of Electrical Wiring System

The entire installation shall be tested in accordance with IEE regulations for:

1.    Insulation resistance.

2.    Earth continuity.

3.    Polarity of single pole switches.

A test certificate shall be submitted in standard performa as directed by the Supervising engineer.

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