Ladder and perforated cable tray are the two types of electrical trays and there are various sizes of cable trays available in the market. It is used to make cable laying and good support. Perforated tray is known as punching tray. Ladder tray is mostly used for underground cables.
Various types of tray fittings joint, bend, elbow, riser and reducer are used in the tray installation work. Instrument cables and control cables are should have to be lay in perforated tray. There are 50 mm, 100 mm, 150 mm, 300 mm, 450 mm, 600 mm,750 mm, 900 mm sizes of electrical cable trays.
Cable Tray Sizes and Cable Tray Types
There are two types of trays are used in the electrical construction. Ladder is mainly used to lay the power cables. 150 mm and 300 mm sizes of ladder is mostly used in the electrical construction. Height of the ladder tray is 125 mm.
Purpose of using – Cable support and laying.
- Ladder Tray
- Punching (or) Perforated
Interview tip: here you can read about electrical cable glands and its types and sizes.
Ladder tray is used to lay the power cables. 100 mm, 150 mm, 300 mm, 450 mm, 600 mm, 750 mm and 900 mm are the available sizes of ladder trays. Height of the tray is 125 mm.
Ladder cable tray sizes: 100 mm, 150 mm, 300 mm, 450 mm, 600 mm, 750 mm and 900 mm.
Constant height: 125 mm.
Purpose of use: Power cables.
Punching or perforated cable tray is used to lay of the control cables. 50 mm, 75 mm, 100 mm, 150 mm, 300 mm, 450 mm, 600 mm, 700 mm and 900 mm are the sizes of perforated tray.
Perforated cable tray sizes: 50 mm, 75 mm, 100 mm, 150 mm, 300 mm, 450 mm, 600 mm, 700 mm and 900 mm.
Constant height: 25 mm.
Purpose of use: Control cables.
Types of Tray Fittings
There are various types of fittings used in the manual tray installation. Sometimes companies does not provides fittings, that situation electricians used to cut a trays with using jigsaw machine.
Fittings: T-Joint, bend or elbows, crossover, inside riser, outside riser, reducer, coupler, joint plate, unistate, spring and nut bolts.
Tools requirement: Spanners, hammer, screwdriver, jigsaw for manual tray cutting.
Installation of Electrical Cable Tray
Trays for supporting cables are recommended for use in warehouses, industrial plants and equipment room, cable trenches, shafts in the building, etc. Steel cable trays, accessories and supports normally be hot dip galvanized or PVC coated and shall be either of the perforated type or ladder. The cable trays shall have adequate strength and rigidity to support the cables installed.
The tray shall be provided with upstands on both sides. All fittings, T-joints, elbows, couplers etc. shall be of substantial sections of the same quality as the trays. Cables shall be fastened securely by purpose made clips, cleats or saddles. Installed in outdoor locations, where in the cables are exposed to the sun shall be provided with sun shade covers secured to the trays adequate ventilation and as recommended by the manufacturers.
Types of Trunking
Cable trunking is a manufactured enclosure for the protection of cables.
Purpose of use: Where applicable, surface and underground(duct) areas.
Cable Trunking Sizes: 50 mm, 75 mm, 100 mm, 150 mm, 200 mm, 225 mm and 300 mm.
Types of Trunking Fittings: Bend, coupler, T-joint, endcap.
Types of Trunking
Adaptable trunking shall be used for power cables and data cables to run parallel in two different compartments with partition. Mini trunking is suitable for surface wiring work indoors where necessitated, either due to aesthetic or technical requirements such as case of extension of existing wiring.
PVC (to know full form) insulated or other insulated cables shall be used in this type of installation. Wherever data cables are used for information outlet, trunking shall be used.
This system using PVC trunking shall be adopted in residential building, or office building where there is a need of tidy wiring system. This type of trunking for distribution of voice data and power should be used for cable management and should accept data socket and power socket or other wiring accessory like switches, indicators etc.
Preferred size of PVC trunking should be 25 x 16 mm, 32 x 16 mm, 40 x 25 mm, 40 x 40 mm and for adaptable trunking it should be 100 x 34 mm or 100 x 50 mm or 160 x 50 mm or 200 x 50 mm.
Installation Method of Trunking
Metallic or Pvc trunking shall be fixed by means of suitable screws to approved type of asbestos or fibre fixing plugs, at intervals not exceeding 60 cm for all sizes for mini trunking. Incase of adaptable trunking, the screwing system shall be such that weight of the trunking and hold firmly on the wall or ceiling. On either side of joints, the distance of the fixing arrangement shall not exceed 15 cm from the point.
All trunking body shall be fixed directly on wall or ceiling as above. Trunking shall be used only on dry walls and ceiling, avoiding outside walls as far as possible and shall not be buried in the walls not fixed in proximity to gas, steam or water pipes.
Trunking shall be with pill off cover for protection against dust. Pill off cover shall be removed only on completion of painting of walls.
PVC Trunking (Casing & Capping)
The wire ways in straight runs should be in single piece as far as possible so as to avoid joints. Trunking shall be of 2 m or 3 m standard for the ease of installation. All joints shall be scarfed or cut diagonally in longitudinal section, and shall be smoothed down by fitting to make the joints a very close fit as far as possible and without burrs.
They shall be screwed at joints with with two or more screws as would be necessary. Joints arising out of the bends or diversion shall be done using standard accessories like internal angle, external angle elbows, T-joint and end caps. For the separation of data cables and power cables there shall be partition in both trunking and accessories. In-riser and out-riser shall have variable angle for alignment at the wall corners.
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