2.5mm ring main and Celotex Insulation

[Roger Perkin]

I am building a garden office and currently have 25mm Celotex in the walls. I am running the ring main around and then want to add some more Celotex.

My question is how much of an air gap do I need to leave for the ring main?

 

[davesparks]

I thought it had to be a ring. It was only another 4m of cable to run it back no big deal - but just need to find out if I can bury the cable in the celotex or if I need to leave air around it?

Which regulation did you get that from?
That is up to you as the designer of the installation to decide, the insulation around the cable will affect the size of cable you use but you will need to do the calculation to work out how much bigger the cable will need to be.

 

[telectrix]

personally i'd run 2 radials. 1 for the heater ona a FCU, and 1 for the sockets. each off a 16A MCB.

 

[Madocks]

personally i'd run 2 radials. 1 for the heater ona a FCU, and 1 for the sockets. each off a 16A MCB.

what about lights?

 

[telectrix]

what about lights?

OP has not mentioned a lighting circuit. i assume that is a separate issue.

 

[Ian1981]

what about lights?

Depending on what the total load is then a 6amp mcb using 1.0mm twin should be fine.
The lowest ccc for 1.0mm is 8amps using table 4D5 depending on other correction factors