Electrical Question

A question about 25mm pvc round conduit.

Is there any reason why two flat twin and earth 1.5mm and one 3 core and earth strapper cables cannot be run in 25mm pvc round conduit?.

2 Answers

Best Answer

Where the cabling of an installation is to be installed in conduit, the conduit system must be designed and installed not only to accommodate the required cables but also to enable them to be easily pulled in once the conduit has been assembled.

A cable being installed in conduit could be subjected to excessive pulling force if it jams or if there is too much friction between the cable and the conduit. Such excessive force may damage the cable insulation, or stretch the conductor, thereby reducing its cross-sectional area and leading to ‘hot spots’, or cause one or more strands of the conductor to fracture, resulting in intermittent or permanent discontinuity.
Regulation 522.8.1 of BS 7671 requires that a wiring system is selected and erected to avoid during installation, use or maintenance, damage to the sheath or insulation of cables and their terminations.

Provided care is taken when drawing in and its a relatively straight run with only one or two bends, then three cables in a 25mm conduit is fine.

This installation method would be classed as installation reference method A (if conduit was buried in the wall) or Method B (if conduit run on the surface)- see link below for more information or refere to tables in BS7671:2008


Answered 14th Feb 2013

Electrical Safety Services

Member since 17 Oct 2011

hi brian

if i can remember rightly you only use 40% of conduit or trunking to allow for heat and eddie currents, to prevent the cables over heating , so i think that amy be a bit tight . hope this helps regards jason .

Answered 14th Feb 2013

jeh electrical

Member since 9 Oct 2012

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