Cable Conduit, Trunking & Routing

To conceal cable conduit trunking into a solid wall you need to follow some basic steps. Firstly you must make a channel in the wall ensuring that it is 6mm wider and 3mm deeper than the conduit you are using. Then cut the conduit to the required length and feed your cable through. This can now be fixed within the channelling using any self-adhesive backing, conduit clips or nails before plastering the wall for a clean neat finish.

Determining cable conduit size

To calculate the conduit size you require, you must first multiply the cross-sectional area of each cable by the appropriate factor, the total factor for each of your cables must not exceed the capacity factor recommended for each conduit diameter.

Conduit Diameter (mm)            Capacity Factor

·         16mm                                           290

·         20mm                                           460

·         25mm                                           800

·         32mm                                           1400

How many cables fit into conduit and trunking?

The recommended maximum fill percentage of a conduit containing just 1 wire is 53%, for 2 wires, the maximum percentage is 31% and if the conduit contains 3 or wires, the maximum percentage is 40%. The size of the conduit you require can all be checked by calculating the cross-sectional area of the wires that will be contained within the conduit.

When incorporating bends within the conduit, it is recommended that 15% is subtracted from the maximum cross-sectional area being used. You should also avoid using 2 or more 90° bends in a single section of conduit.

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