SECTION - 8212

8212-6SECTION - 8212

LOW VOLTAGE CABLE

1.0SCOPE OF WORK

The work under this section consists of supplying, installing, testing and commissioning of all material and services of Low Voltage cables and the accessories as specified herein or as shown on the Tender Drawings and in the Bill of Quantities.

The Contractor shall discuss the electrical layout with the Engineer and coordinate at site with other services for exact route, location and position of the electrical lines.

The LV cables with accessories shall also comply with the General Specifications for Electrical Works Section-8001 and with other relevant provisions of the Tender Document and latest WAPDA specifications.

2.0GENERAL

All single core PVC insulated cables for the following shall be of 600/1000 volt grade copper conductor cables;

-wiring of light circuits

-switch to point wiring

-light point to light point wiring

-wiring of circuits for 5 amps, 250 volt, 2&3 pin switch socket unit

-wiring between 5 amps, 250 volt, 2&3 pin switch socket units

-wiring of push buttons & Between Push Buttons

-wiring of light circuits controlled by push buttons

-wiring between light circuits controlled by push buttons

All single core PVC insulated power cables for the following shall be copper conductor and of 600/1000 volt grade:

-wiring of circuits for 15 amps, 250 volt, 3 pin switch socket unit

-wiring between 15 amps, 250 volt, 3 pin switch socket units

-wiring of circuits for 20 amps, 250 volt, 3 pin switch socket unit

All multicore unarmoured control cables shall be copper conductor and of 300/500 volt grade.

All multicore unarmoured power cables shall be copper conductor and of 600/1000 volt grade.

All multicore armoured power cables shall be copper conductor and of 600/1000 volt grade.

3.0APPLICABLE STANDARDS/CODES

The latest editions of the following standards and codes shall be applicable for the materials within the scope of this section:

BS 6004-PVC insulated cables (non-armoured) for electric power & lighting

BS 6346-PVC insulated cables for electricity supply

BS 6746-PVC insulation and sheath of electric cables

BS 6360-Conductors for insulated cables

IEC 228-Conductors for insulated cables

BS 6500-Insulated flexible cords

4.0MATERIAL

4.1General

The power, lighting and control cables shall be furnished and installed in accordance with the details shown on the drawings. The general guide lines and criteria for reference is given below:

4.1.1Phase Identification

All cables shall have phase identification colors on insulation of each core. The colour code for three phase circuits shall be;

-Red, Yellow and Blue for phase conductors.

-Black for neutral conductor.

-Green for earth conductor where PVC insulated cable is installed.

Single phase circuits shall have insulation of;

-red colour for phase/line

-black colour for neutral

-green colour for earth conductor.

All DC circuits shall have insulation of;

-Red colour for positive conductor

-black colour for negative conductor

-green colour for earth conductor.

4.1.2Cable Accessories

All accessories shall be provided for the complete cabling and wiring systems. These shall include but not limited to items such as saddles, clamps, fixing channels, connectors, cable joints (where necessary and as approved by the Engineer), clips, lugs, tapes, solder, identification tags, bushes, glands, etc.

5.0INSTALLATION

5.1Conduit Wiring

The wiring through conduit shall be started only after the conduit system is completely installed and all outlet boxes, junction boxes, etc., are fixed in position.

The wires shall be pulled in conduit with care, preferably without the use of any lubricant. Where necessary and after approval of Engineer, the cable manufacturer's recommended lubricant shall be used. Use of any kind of oil or soap will not be permitted. Where several wires are to be installed in the same conduit, they shall be pulled together alongwith the earth conductor. All wires of same circuit shall be run in one conduit.

The wires shall not be bent to a radius less than ten times the overall diameter of the wire, or more if otherwise recommended by the manufacturer.

The wiring shall be continuous between terminations and looping-in system shall be followed throughout. Any joint in wires shall not be allowed. The use of connectors shall only be allowed at locations where looping-in is rendered difficult. The consent of the Engineer shall be required for using connectors. The connector shall be of suitable rating having porcelain body, sunk-in screw terminals. The connector shall be wrapped with PVC insulation tape after its installation. A minimum of 150 mm extra length of cable/wire shall be provided at each termination to facilitate repairs in future.

5.2Cables on Surface

All cables for installation on surface of wall, column, ceiling, etc., shall be fixed to the surface by means of galvanized steel clips secured to a steel channel by means of suitable stud plate, nuts and washer. The distance between each cable clip to be such, so as to support the entire weight of the cable and that, distance between the cable and surface and also the vertical clearance between two adjacent cables at any point is 50mm minimum. Common mounting channels are to be furnished for cable along the same route. The Engineer before commencement of installation shall approve alternate cable fixing arrangement, which the Contractor can offer.

5.3Cables in flexible/rigid conduits on surface

All cables for on surface conduits shall be installed through the conduits without the use of lubricants. The flexible/rigid conduits shall be fixed to wall/ceiling surface by means of cable clamps using rawl plays and galvanized screws.

5.4Underground Cable

The cables to be installed directly underground shall be laid in trench in single ties. The depth of cable under ground, shall be three feet minimum, measured from the top of the largest cable to the general ground level. The burial depth may be increased as required due to site conditions or when crossing other service pipes and roads. Burial depth less than three feet and more than five feet shall require Engineer's approval.

When cables cross road, paved area, other services or other cables, they shall be laid in protective pipes of required size. Cables entering the buildings shall also be laid in protective pipes. The protective pipe ends, after installation of cables shall be plugged water tight by means of bituminised resin or equivalent method as approved by the Engineer. A minimum clearance of ten inches vertically and 20 inches horizontally shall be maintained between cables and other services.

Cable identification tags of corrosion resistant material shall be tied to cables with bronze wire at a maximum of 65 feet interval along the cable length for identification of cable and circuit. Above ground cable markers of 8 SWG (4 mm) sheet steel and 200 mm2 shall be erected at 100 feet intervals along the straight trench, and at each bend and joint box for indication of presence of underground cable. For more than three feet wide trenches, cable markers shall be provided at both edges of the trench. The cable marker shall be finished in gray heavy enamel paint over two base coats of anti-rust red oxide paint, with the necessary instructions indicated in approved colours.

The Contractor shall furnish samples of cable marker for approval of Engineer before installation. The marker shall be welded to an angle iron fixed to the ground on a cement concrete base or as directed by the Engineer. The earth continuity conductor shall be laid in the trench with the cables. The Contractor shall submit to the Engineer for approval, schedule of cable markers showing location of marker and instructions on each.

The cable trench shall be excavated as per route and location shown on the drawing. Before laying of cables in the trench, the bed of the trench shall be leveled and filled with a four inch thick layer of fine sand (1/32 inch diameter maximum particles size). The sand layer shall be leveled and the cables placed thereon, the cables shall be covered with a layer of fine sand Four inch thick measured above the top of the largest cable.

The cable protective bricks placed above the top of sand cover shall be of Class - C cement concrete, minimum Two inch thick and 12 inches x 12 inches square or as approved by the Engineer. The bricks shall be placed over the sand layer end to end to cover the entire length and breadth of the cable trench, after the concrete bricks are placed, the remainder of the trench shall be backfilled with earth in layer 16 inches thick. Each layer shall be thoroughly tamped and compacted.

Sufficient slack shall be left in cables for which purpose the cut lengths of cables shall also about 3% more in the measured lengths between terminations. At underground joint box, ample slack shall be left to prevent straining of cable joints due to settlement of the cable trench.

The cut lengths of cables wherever stated are only as a guide. The Contractor shall measure actual lengths between terminations of each circuit and if the discrepancy between measured lengths at site and where given on the drawing differ by more than +10% the Contactor shall report to Engineer and act as directed. Cables, whether installed underground, or in cement concrete trenches, shall not be bent to a radius less than that recommended by the cable manufacturers.

6.0MEASUREMENT AND PAYMENT

6.1General

The Contractor's bid amount against each Bill of Quantities item as given below shall include supply, installation, testing, commissioning and completion for all work specified herein and/or as shown on the Tender Drawing related to the item.

6.2Light Circuit Wiring

6.2.1Measurement

Measurement shall be made for the total number of light circuit wiring from LV distribution board/LV switchboard to point/switch including wiring between switches on same circuit, acceptably carried out by the Contractor as a complete unit.

6.2.2Payment

Payment shall be made for the total numbers of units measured, as provided above, at the Contract unit price each. The payment shall constitute full compensation for supplying, installing, connection, testing, commissioning and completion of the circuit wiring from the LV switchboard/LV distribution board to point/switch including wiring between switches on same circuit complete with conduit, wire/cable, earth continuity conductor, accessories, etc.

6.3Light/Fan Point/Point to Point Wiring

6.3.1Measurement

Measurement shall be made for each light point, wiring between the light point and switch, point to point, acceptably carried out by the Contractor as a complete unit.

6.3.2 Payment

Payment shall be made for the total numbers of units measured, as provided above, at the Contract unit price each. The payment shall constitute full compensation for supplying, installing, connecting, testing, commissioning and completion of the wiring between light point to switch and point to point including required size of cable, conduit, earth continuity conductor, flexible cable, ceiling rose, accessories, etc.

6.4Wiring of Lights Directly Controlled from Distribution Board/Local MCBs/Wiring of Push Buttons

6.4.1Measurement

Measurement shall be made for wiring of each light point directly controlled from distribution board or local MCBs type switch and wiring of push buttons acceptably carried out by the Contractor as a complete unit. 6.4.2Payment

Payment shall be made for the total numbers of units measured, as provided above, at the contract unit price each. The payment shall constitute full compensation for supplying, installing, testing and commissioning of wiring of light points directly controlled from distribution boards or local MCB type switches and wiring of push buttons including required size of wire, conduit, earth continuity conductor, flexible cable, ceiling rose, accessories, etc.

6.5Wiring of 5Amps, 250Volt Combined 2 & 3 pin Switched Socket Unit from LV switchboard/Distribution Board

6.5.1Measurement

Measurement shall be made for number of points for wiring of 5Amps, 250 Volt, combined 2 & 3 pin switched socket unit acceptably carried out by the Contractor as a complete unit.

6.5.2Payment

Payment shall be made for the total numbers of units measured, as provided above, at the contract unit price each. The payment shall constitute full compensation for supplying, installing, connecting, testing, commissioning and completion of wiring for 5 Amps 250 Volt, combined 2 & 3 pin switched socket unit from LV switchboard/ distribution board including specified size of single core PVC cables including conduit, ECC, PVC conduit, accessories etc. complete in all respects.

6.6Wiring between 5Amps, 250Volt Combined 2 & 3 pin Switched Socket Units

6.6.1Measurement

Measurement shall be made for number of points for wiring between 5Amps, 250 Volt, combined 2 & 3 pin switched socket unit acceptably carried out by the Contractor as a complete unit.

6.6.2Payment

Payment shall be made for the total numbers of units measured, as provided above, at the contract unit price each. The payment shall constitute full compensation for supplying, installing, connecting, testing, commissioning and completion of wiring between 5 Amps 250 Volts, combined 2 & 3 pin switched socket unit including specified size of single core PVC cables including conduit, ECC, PVC conduit, accessories etc. complete in all respects.

6.7Wiring of 15Amps, 250Volt 3 pin Switched Socket Unit from LV Switchboard/Distribution Board/Bus Bars

6.7.1Measurement

Measurement shall be made for number of points for wiring of 15Amps, 250 Volt, 3 pin switched socket unit acceptably carried out by the Contractor as a complete unit.

6.7.2Payment

Payment shall be made for the total numbers of units measured, as provided above, at the contract unit price each. The payment shall constitute full compensation for supplying, installing, connecting, testing, commissioning and completion of wiring for 15 Amps 250 Volt, 3 pin switched socket unit from LV switchboard/distribution board/Bus Bars including specified size of single core PVC cables including conduit, ECC, PVC conduit, accessories etc. complete in all respects.

6.8Wiring between 15Amps, 250Volt 3 pin Switched Socket Units

6.8.1Measurement

Measurement shall be made for number of points for wiring between 15 Amps, 250 Volt, 3 pin switched socket unit acceptably carried out by the Contractor as a complete unit.

6.8.2Payment

Payment shall be made for the total numbers of units measured, as provided above, at the contract unit price each. The payment shall constitute full compensation for supplying, installing, connecting, testing, commissioning and completion of wiring between 15 Amps 250 Volt, 3 pin switched socket units including specified size of single core PVC cables including conduit, ECC, PVC conduit, accessories etc. complete in all respects.

6.9Wiring of 20Amps, 250Volt 3 pin Switched Socket Unit from LV Switchboard/ Distribution Board

6.9.1Measurement

Measurement shall be made for number of points for wiring of 20 Amps, 250 Volt, 3 pin switched socket unit acceptably carried out by the Contractor as a complete unit.

6.9.2Payment

Payment shall be made for the total numbers of units measured, as provided above, at the contract unit price each. The payment shall constitute full compensation for supplying, installing, connecting, testing, commissioning and completion of wiring for 20 Amps 250 Volt, 3 pin switched socket unit from LV switchboard/ distribution board including specified size of single core PVC cables including conduit, ECC, PVC conduit, accessories etc. complete in all respects.

6.10LV Cables

6.10.1 Measurement

Measurement shall be made for the number of running feet for each size and type of LV cable acceptably supplied and installed by the Contractor.

6.10.2 Payment

Payment shall be made for the number of running feet of each size of cable measured, as provided above, at the Contract unit price each and shall constitute full compensation for supplying, installing, connecting, testing and commissioning of the LV cables including all accessories.

6.11Excavation of Cable Trench

6.11.1 Measurement

Measurement shall be made for the number of cubic feet for excavation of each size of cable trench acceptably carried out by the Contractor.

6.11.2 Payment

Payment shall be made for the number of cubic feet of excavation for each size of cable trench measured, as provided above, at the Contract unit price each and shall constitute full compensation for excavation of the LV cable trench in ordinary soil and slightly rocky site.

6.12Backfilling of Cable Trench

6.12.1 Measurement

Measurement shall be made for the number of cubic feet of backfilling for each size of cable trench acceptably carried out by the Contractor.

6.12.2 Payment

Payment shall be made for the numbers of cubic feet of backfilling for each size of cable trench measured, as provided above, at the Contract unit price each. The payment shall constitute full compensation for four-inch thick sand bed, four inch thick sand cover, cable protective tiles/bricks, backfilling of already excavated earth, watering, compaction, consolidating, etc. complete to the satisfaction of the Engineer