Carcassing/Cellotex/Wiring

[Draughtsman]

I'm aware of the rules re cables/sockets in render/plaster, but behind plasterboard/insulation/studwork?

I'm probably using 63mm carcassing with 50mm insulation boards so there will be a half inch at the back for cable clips. Are there any rules about where the socket cables can't go in this situation?

 

[chivers67]

As long as they are run in "Safe Zones" and you calculate for any derating factors where it runs or passes through the actual insulation it sounds like it should be ok

 

[ban-all-sheds]

As long as they are run in "Safe Zones" and you calculate for any derating factors where it runs behind or passes through the actual insulation it sounds like it should be ok

 

[Draughtsman]

Derating?

 

[Taylortwocities]

Derating?

The current carrying capacity for cables can change (usually reduce) depending on a number of factors. these include envinonment, installation method, and others.

So if you install a cable that is completely surrounded by insulation, you may need to put a much thicker cable in, or it may overheat and catch fire.
The same cable which is clipped to a wall, and is in contact with insulation on one side will have a reduced current carrying capacity, but will not be reduced as much as the cable in the other example, above.

So, calculations need to be done,taking the environmental effects into account.

It's all part of an electrician's training, and BS7671.

 

[ban-all-sheds]

http://www.batt.co.uk/upload/files/4d5.pdf

 

[Draughtsman]

So I just find the worst case option, like passing thru 50mm of Cellotex to access a few sockets, and use that size cable all round?

Would that be heavier gauge than that used under cable capping/render/plaster?

 

[Taylortwocities]

Yes(ish) and yes.
There are other factors.
Got instance: voltage drop (see last col in BAS’s table).
A particular cable may seem to be the right size for a particular installation method, but we also have to determine if there will be enough volts at the end of the circuit to boil the kettle or whatever the load is.