Ring main mcb

[iamlee2002]

Hi all have done some work upstairs in house put new wiring up there for the sockets. Used 2.5mm t&e for the ring, however some of the cables run through 100mm insulation and some through 50mm insulation acoustic type. What size mcb should I use? I have done some digging about some days 32a be fine some say 25a is more logical? Thanks in advance

 

[Taylortwocities]

If you have run 2.5mm² T&E through insulation then Its not the MCB you need to consider. You may need to replace the wiring with a larger CSA cable. 4mm² maybe.

What did your cable calculations say when you applied Ci and/or the reference method?

 

[iamlee2002]

The old radial circuit was on a 20 and ran through longer lengths of the insulation not much of the cable is in insulation only where it runs up to the socket 450mm each socket that's on top of the 50mm insulation not behind it.

 

[ban-all-sheds]

The old circuit is irrelevant - you have done away with it, and it may not have been correctly sized in the first place.

What did your cable calculations say when you applied Ci and/or the reference method?

 

[iamlee2002]

Re ran the route last night to avoid insulation required more cable but now thanks for advice all

 

[ban-all-sheds]

You did make sure you complied with the regulations for where concealed cables may run?

 

[iamlee2002]

Yes