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1. Conduit Wiring and Installation Methods

Conduit wiring is a system of wiring using tubes (pipes) either steel or PVC, to provide good mechanical protection for its conductors drawn inside the tubes. It also gives high degree of protection from fire hazards to its conductors. Conduit pipes will be installed on the surface of walls or roofs by means of saddles or hooks or concealed inside the wall or roof or floor.

Modern building construction adopts conduit wiring (PVC conduit or GI conduit both in various mechanical strength depending on site requirement and project specification) and found mainly in two types: 1) Surface or Open type conduit installation, and 2) Recessed or Concealed type conduit installation.

Steel Conduits and Fittings are made out of heavy / medium / light gauge steel. It uses different technologies for manufacturing these tubes depending its thickness and surface treatments.

Galvanized Rigid Steel Conduit is recognized as the safest and most protective form of electrical raceway. It is important that steel conduit provides excellent physical / mechanical protection for wiring, and also acts as a ground shield, reducing EMI (electro-magnetic interference due to field emission) and minimizing any effect of external RFI (radio frequency interference). It is also act as an equipment ground conductor in a circuit, thereby reducing wiring requirements and simplifying installation. Steel Conduit can be installed indoors and outdoors, in dry locations or wet locations, exposed or concealed, in all atmospheric conditions and in hazardous locations.

Galvanized Electrical Metallic Tubing (EMT) is similar to rigid steel conduit but is much lighter, weighing approximately 40 percent as much as rigid steel conduit of the same nominal size. EMT can be used for both exposed or concealed work provided, where during installation or afterwards, it is not subjected to severe physical damage. Use of EMT is restricted to systems not exceeding 600 volts and to non-hazardous locations except (Class II Division 2 NEC Section 502-4 (b). Galvanized Steel EMT installed in concrete on grade or above generally requires no supplementary corrosion protection. However, when installed in concrete below grade level and in contact with soil or cinders supplementary corrosion protection consisting of a protective coating of bitumastic or asphalt base paint or plastic is generally applied. According to NEC Section 348-1, EMT run in or under permanently moist cinder fill must be encased in at least two inches of cinder free concrete unless the conduit is at least 18 inches below the fill.

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:

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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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