Definici´ on del problema

SECTION 8

CONDUITS/TRUNKING/CABLE TRAYS LADDER, FITTINGS AND CABLE MANAGEMENT SYSTEM

INDEX

1.0 CONDUITS AND ACCESSORIES 2.0 FLEXIBLE CONDUITS

3.0 CONDUIT INSTALLATION 4.0 GENERAL WIRING TRUNKING 5.0 CABLE TRAYS/CABLE LADDERS

6.0 DADO TRUNKING / SKIRTING TRUNKING 7.0 SERVICE OUTLET BOXES

8.0 WIRE BASKETS

1.0 CONDUITS AND ACCESSORIES

All conduits embedded in concrete, plaster and screed unless otherwise specified shall be extra heavy wall black PVC and shall conform to BS 4607. All exposed conduits shall be heavy gauge, welded, screwed and galvanized steel in accordance with BS 4508.

PVC Conduits shall be black of the extra heavy wall with 1.8mm minimum thickness for 20mm dia conduit.

Steel conduits shall be of the heavy gauge galvanized steel, welded and screwed type zinc coated, hot dipped galvanized both inside and outside.

All set, fixing and wood screws used throughout the installation shall be brass.

Accessories mounting box shall be provided with brass earth terminal and shall be supplied with adjustable steel grids.

Conduit boxes for steel conduit systems shall be malleable iron with screwed spout outlets, blind cover fixing holes, galvanized and water proof with external lugs where required.

Each steel conduit thread shall be given a coat of aluminium paint upon completion of conduit installation.

All circular PVC boxes where used to support lighting fittings shall be provided with steel insert clips.

The sizes of the conduits for all wiring shall be in accordance to IEE regulations and DEWA Standards and shall be such that a cable can be withdrawn and another drawn in without disturbing the remainder. However, the size of the conduit shall not be less than 20mm where used for lighting and power circuits and 25mm for telephone / data wiring.

2.0 FLEXIBLE GI CONDUITS

PVC sheathed and watertight Flexible metal conduits, shall be provided between the conduit system and electrical motors or other apparatus subject to vibration. They shall be complete with brass double female adaptors and will be soldered to either end of all flexible conduits and connected to solid conduit entries using smooth bore male brass bushes.

Earth continuity through flexible conduits shall be provided by a separate earth continuity conductor, sized in accordance with BS Standards. The brass adaptor specified above shall be drilled so that the earth wire can be brought out at each end. The earth wire shall be soldered at each end to the brass adaptors or alternatively connected to a substantial earth terminal.

3.0 CONDUIT INSTALLATION

All joints in PVC conduits, other than screwed joints, shall be cemented with a waterproof adhesive. This adhesive shall be as recommended by the conduit manufacturer.

Screwed connections between steel conduits and accessories shall be screwed up tight, where coupled by a socket the conduit ends shall butt together; running joints shall be provided with back nuts which shall be screwed up tight.

PVC conduits shall be saddled at a minimum of 1 metre intervals. All saddles, tubes and boxes must be in perfect alignment to avoid any appearance of warping when the

installation is complete. Saddles should not be so tight as to prevent expansion of the

All ceiling boxes concealed in ceiling slabs or voids above false ceilings shall finish flush with the underside of the ceiling and all necessary extension or break joint rings shall be provided and fitted.

Steel conduits which finish at boxes or other equipment without smooth bore spouts shall be fitted with smooth bore bushes, the inside diameter of which shall be equal to the bore of the conduit. The junction shall be made by means of a male to female threaded socket bearing on the outside of the box and into which shall be screwed from the inside of the box a hexagon smooth bore male bush.

Plain or inspection elbows, or tees, will not be permitted and the number and position of boxes and sizes of conduits shall be arranged to permit the cable being drawn-in easily after all conduits have been erected. Stock bends below 38 mm diameter will not be allowed; all such bends shall be formed out of the conduit at Site to suit the local conditions. Sets and bends shall be made without indentation and the bore shall remain full and free throughout.

Conduits shall not be run closer than 0.15m to any steam or hot water pipes and shall be run underneath such pipes rather than over them. The conduits shall not be run closer than 0.05m to any telephone, bell or other signalling circuit.

No wiring or drawn-in wires, cables or wires of any description are to be drawn into the conduits until the section of the conduit system involved is complete.

A separate conduit and wiring system is to be provided for each installation i.e. lighting general purpose sockets, power, telephone, etc.

Drawn-in boxes must be provided to give access to all conduit for the drawing-in or out of any cable after the installation is completed and should not be spaced more than 9m on straight runs. On runs with not more than two right angle bends the spacing between draw-in boxes shall not exceed 7m.

Not more than two right angle bends shall be installed between boxes. Conduits shall not be laid to falls, but the Contractor shall exercise care to ensure that no pockets are formed within the conduit system in which water can collect. Drainage holes shall not be provided.

In floors which are in direct contact with the earth or under which unheated foundation voids are situated, conduits shall not be laid to form traps in which moisture can collect.

Where it is impossible to arrange for drainage to a lower level such floors shall be avoided altogether and the conduit shall be run in the floor above with drops to socket outlets and other low level points.

Embedded conduits shall be fixed in position by crumpets or such other means of fixing as shall be necessary to ensure that they remain rigidly in structure or finishes.

Where steel conduits enter sheet steel wiring trunking, iron clad gear or junction or similar boxes, the junction shall be made by means of a flanged coupling with lead washer bearing on the outside of the box and into which shall be screwed from the inside of the box a hexagon smooth bore brass male bush of heavy pattern.

Where PVC conduits connects to any sheet steel wiring trunking, steel clad switchgear and the like, these shall be connected to the PVC conduit system with female thread to plain push-in adaptors with a male bush or with male thread to plain push-in adaptors with locking ring as may be required.

Steel conduits which do not finish at boxes with smooth radiused inside spouts shall be fitted with smooth bore bushes, the inside diameter of which shall be equal to the bore of the conduit.

Where conduits cross a building expansion joint due allowance shall be made in the design of the run with an approved expansion joint.

All screwed joints for conduits and fittings erected in the open air, damp situations and plant room shall be made water-tight by the application of a suitable metallic paint and conduit boxes being fitted with rubber gasket. Separate earth continuity conductors will be installed within the normal circuit wiring.

The conduit system shall be such that 'cross-overs' are reduced to a minimum and runs shall be located to avoid holes in the floor slabs required for other services.

Particular care shall be taken to ensure that no grout or other foreign materials enters the conduit system through joints, or through surface openings. Screw holes in boxes must be kept entirely free and clean. After screeding, compressed air is to be blown through the conduit system to ensure that it is clean and a steel draw wire of adequate size to be pulled through to ascertain that no obstruction is adhering to the inside of the conduits.

Draw wires shall be left in all conduit runs for other services not included in the contract.

4.0 GENERAL WIRING TRUNKING

Cable trunking, ducting and fittings should comply with BS 4678 Standards. All cable trunking accessories such as bends, tees, cable retainer, cable separators, reducer and support shall be supplied from the manufacturers standard product range. Site fabricated accessories shall not be acceptable.

Cable trunking shall be of sheet steel fabrication, galvanized to with heavy protection both inside and outside. The access plate of the trunking shall be removable in easily-handled sections over the entire length of straight runs. Overlapping collar sections or other similar approved linking arrangement shall be provided at the junction of the various sections of the trunking.

All fixings shall be so arranged that there are no projecting screw threads or similar points within the trunking which may cause damage to the cables. The section of the trunking shall not be so changed at deviations from the straight as to decrease the cross- sectional area.

Positive continuity links shall be supplied and fixed at all trunking section interconnection points.

Cable trunking shall not be installed to expose to other mechanical stress except the loads associated in carrying cables.

Spacing of supports for cable trunking shall be as recommended by the standards, supports shall be positioned within 300 mm of each bend or fittings.

A calculation for the space factor shall be forwarded for approval and the trunking shall be sized accordingly.

5.0 CABLE TRAYS/CABLE LADDERS

Cable tray and cable ladder shall be produced to BS 729 and shall be hot dip galvanized.

Prefabricated mild steel cable trays shall be constructed of steel and finished hot dipped galvanized. All trays supporting power cables shall be folded edge heavy duty tray with return flange and those supporting fire alarm and telephone cables shall be medium duty.

Sheet steel thickness for cable trays shall be as indicated hereunder for the different sizes and types:

- Heavy Duty : 100mm to 300mm 1.5mm 450mm to 600mm 2.0mm

Cable trays, bends and junctions shall be provided as necessary and shall be similar type and finish. The trays shall be of adequate widths to support the necessary cables. They shall be adequately supported throughout the length or run at intervals not exceeding 1200 mm. All cables shall be fixed to the cable tray utilising cable ties. Ventilated covers shall be provided for all cable trays exposed to direct sunlight.

Cable ladder shall be produced of 2mm hot dipped galvanized mild steel.

Only 40% of the cable tray and the cable ladder space shall be occupied. Cable tray size calculations shall be forwarded for approval and the tray size shall be increased, if required, to meet the above without any extra cost.

6.0 SKIRTING / DADO TRUNKING

The trunking shall be provided as per the requirements of BS 4678 partly and BS 4662. The uPVC trunking shall be either installed skirting level or DADO level as shown on drawings.

The system shall comply with all relevant requirements of 16^th edition of wiring regulations and structured cabling Standards.

All corridors, extension corridors, covers, and cable dividers shall be extruded. Corners, corner covers, stop ends cover seals and accessory boxes must be formed by injection moulding.

It is the responsibility of the contractor to provide a proper arrangement and installation of the system to engineers requirements and all necessary interconnecting junction boxes, risers, joints etc to be provided.

The trunking cover shall be uPVC to incorporate all outlets.

Sizes of Trunking shall be as shown on drawings with two / three compartments, for power and voice / data.

Sockets shall be from the same manufacturer of trunking flush with the cover. Voice data outlets shall be supplied under structured cabling contract. Back box and face plate shall be provided by the skirting system vendor.

Backboxes shall be provided as required for conduit drops.

Refer detailed specifications in Medical Services Installation (Part A – Section 10) for service panels / bed head units.

7.0 SERVICE OUTLET BOX

Service outlet boxes shall be two-compartment type of the size 300x 300 x75-90mm and shall be constructed from high-pressure Zinc Alloy die casting base frame pillars.

This shall be fixed on to heavy gauge galvanized steel base plate for support by support frame. Other materials adequate in strength and performance shall be used and these shall be protected against corrosion. The boxes shall be constructed with provisions for ducting or conduit access on all four sides. Unwanted entries shall be blanked off with detachable side blanks.

Covers for service outlet boxes shall be made of high pressure Zinc Alloy die casting with 12mm recess to receive ceramic tiles or carpet tiles. They shall be lifted by suction cups as and when required giving access at all times to the power, telephone and ELV outlets. Counter sunk screws shall secure the covers of service boxes. All exposed portions of the boxes shall be epoxy coated in grey color.

All boxes shall have extra wide gaskets in order to minimize water seepage. Gaskets shall be made of material that is durable in order to withstand loads.

All boxes shall be adjustable in height to take account of difference in floor thickness.

Cables emerging from service boxes shall be protected against damage by means of nylon cable exit grommets or equivalent and approved material and shall be reversible to close position when not in use.

Circuit protective conductors shall be provided between the covers and the boxes.

The boxes shall be adequate in strength to take in a ceramic tile, and withstand loads normally seen in airports and pubic locations.

8.0 STEEL WIRE BASKETS

Baskets shall be constructed from 5mm steel wires. The spacing between longitudinal wires shall be 50mm and between transverse wires 100mm. The steel wires shall be welded at all joints. Transverse wires shall be “T“ welded to top edge longitudinal wires in such a way so as to minimise fraying of the cables when being laid.

The steel wire baskets shall be Electro-Zinc galvanized and corrosion resistant.

Wire baskets shall be minimum 50mm high and, 150mm / 200mm / 300mm / 400mm / wide as may be specified elsewhere or as shown in layout drawings.

INSTALLATION

Steel wire baskets shall be installed as shown in layout drawings as per manufacturer’s instructions. Installation shall be carried out only after obtaining approval of

representative samples of baskets & accessories from the Engineer.

Purpose made accessories such as couplers, brackets & supports, fittings, dividers &

covers as may be specified else where, only shall be used for the installation of wire baskets. All accessories shall be so constructed so as to permit easy and quick assembly and installation.

Equipotential earth bonding shall be carried out as per manufacturer‘s recommendations.

SECTION 9