Selection and Sizing of Cable Tray

In the Electrical wiring of building, a Cable tray System is used to support insulated electrical cables like distribution cables, control cables and communication cables.

Types of Cable Tray

1. Ladder Type

2. Perforated Type

Ladder Type Cable Tray :

    Ladder Type Cable trays are used in the area where the trays have large span, more number of cables and highly heat production in cables. 

1. For larger span, using of perforated type cable tray will cost higher compared with ladder type.

2. More number of lager size cables with more current, produce heat in the cables. So ladder type tray is used to dissipate the heat more effectively due to free air flow.

LADDER TYPE CABLE TRAY

Perforated Type Cable Tray :

    Ladder Type Cable trays are used in the area where the trays have smaller span, and low heat production in cables. 

1. For smaller span, fabrication of ladder type cable tray is difficult. perforated Type Cable trays are easy to fold, no need for fabrication.

2. Perforated Type Cables are very useful in case of control cable routing and low capacity cable distribution.

PERFORATED TYPE CABLE TRAY

Standard size of the Cable Tray :

WIDTH (in mm)

50, 75, 100, 150, 200, 300, 400, 450, 600, 750, 800, 900

DEPTH (in mm)

20, 50, 75, 100, 150, 200

LENGTH - 2500 mm

Calculation of Cable Tray Size :

Example : Sizing of Cable Tray having cables of 3Rx3.5Cx400 Sq.mm Al.Ar Cable, 2Rx3.5Cx120 Sq.mm Al.AR Cable, 1Rx3.5Cx70 Sq.mm Al.Ar Cable.

By using the above chart, we can know the overall diameter of the cable. This is the cable manufacturer chart. value given in the chart may vary slightly for all other manufacturer.

Sizing :

From the Above Chart - Overall all diameter of 400 Sq.mm Cable is 70mm

Overall diameter of 120 Sq.mm Cable is 41mm

Overall diameter of 70 Sq.mm Cable is 34mm

         1. 3R x 400 = 3*70

                             = 210 mm

          2. 2R x 120 = 2*41

                             = 82 mm

          2. 3R x 70  = 1*34

                             = 34 mm

Total of all overall diameter of the cable = 210 + 82 + 34

                                                                = 326

Add Extra 40 % for Future Purpose        = 326 + (40% of 326)

                                                                = 326 + 130

                                                                = 456

Look up the standard size of the cable tray, pick the cable tray which is higher to the 456. We can select 600mm Cable tray for this cables.

To choose the depth of the cable, we have to lookup for higher rating cable. In this, High Diameter cable 400 Sq.mm which is 70mm Diameter. So we can choose depth of the cable tray to 100mm.

We have to leave the space between the Cables of about 25% of its size .

Sized Cable Tray - 600 x 100 mm Cable Tray. We can choose perforated or Ladder Type as per our requirement.