Ventilated trunking

Greg: · Jul 2, 2012

I'm working out a plan a house rewire where the supply comes into the garage. The trouble is that I dont want to just clip cables to the wall, the garage is not plastered so that eliminates the possibility of sinking the cables below the wall surface and placing the cables in conduit or trunking would change the reference method to B. Then, as far as appendix 4 is concerned, the necessary spec of a lot of the wiring would be raised.
All that would be needed is less than a metre of trunking to take the cables vertically up to the ground floor ceiling.
Perhaps I'm being pedantic but I'm wondering what's the problem with the trunking?
All it would take would be for the top (and perhaps the bottom) of the trunking to allow ventilation. Presuming that the trunking gave sufficient internal space for the circulation of air, I'm sure that the wiring it contained would be kept cooler than wiring buried in plaster.
At the end of the trunking entering the void between the floors the trunking could be simply left open. Alternately some sort of lid with an rating of IP--X would give protection and still permit ventilation.
Or am i missing something?

Rockingit · Jul 2, 2012

Without knowing a bit more it's hard to give a precise answer, but I'd have thought that using a larger size steel conduit would work perfectly well. The issue with heat is in the grouping of the cables, so in a short length of cold steel in a garage, with room to move, shouldn't be an issue. Remember to earth it!

telectrix · Jul 2, 2012

i think you are over thinking this one. a slong as the trunking is big enough to allow air space around the cables, don't worry. alternatively, could you use a piece of tray?

HandySparks · Jul 2, 2012

Just as an example, here's a job I was involved with at a club I belong to (not primarily designed by me). Not domestic, not really "industrial" either, but in a workshop. Maybe we overthought it, but wanted to play it safe. Mechanical protection of the cables and full ventilation. Some cables are run close to their limit (distribution to other board with 50A of panel heaters, for example). The mesh is stainless steel. Not too expensive from a local steel stockholder.