2.5mm on 32A MCB

[kingeri]

Just wondering what folks would do if you came across this on your travels. 4mm radial sockets circuit, on 32A MCB. Two branches from the CU, one supplying 6 double sockets, wired entirely in 4mm, so fine. The other branch consists of a 1m run of 4mm to a double socket, then around 5m in 2.5mm cable on to a second double socket.

The question is, who would be happy to leave this arrangement in place, and who would downgrade the breaker to 20A? I would say it's ok, as the 2.5mm can't be overloaded as it feeds only one double socket, just like an infused spur off a ring.

 

[Toneyz]

if you look at Fig 15B BYB it shows a 32a 4.0mm radial with a unfused spur to double socket via j.b. wired in 2.5 .I would rather like to see it in 4.mm or on own 20A prothctive device.

 

[westward10]

I will C2 it all day.

 

[kingeri]

I will C2 it all day.

Which reg is it contravening?

 

[westward10]

The cable is not suitably protected against overcurrent, this is how I see it.

 

[The Ghost]

In design terms cable must carry less than or equal to the protective device. i.e. 32a protecting a 17a ccc does not meet this criteria. Look up Ib In Iz and try not to make me do it please Dammit...433.1.1

 

[DPG]

In design terms cable must carry less than or equal to the protective device. i.e. 32a protecting a 17a ccc does not meet this criteria. Look up Ib In and try not to make me do it please

Look up non-fused spurs from an RFC. Haven't got the regs in front of me but would be interested to see what they say. Appendix 15. Daz

 

[westward10]

Which reg is it contravening?

How is the 4mm installed.

 

[FatAlan]

I thought Iz had to be greater than or equal to In otherwise the cable would fail before the protective device?

 

[The Ghost]

Appendix 15 shows one double socket is ok only. That is in 2.5, but I think if I came across that I would advise the client this is potentially hazardous, and in design terms fails on 433.1.1 although I could just about believe one double socket may not overload 6 sockets have a high potential to do so. Anyway if I was installing the circuit I would no way do it that way.

 

[The Ghost]

Yeh you are right thats what 433 etc. says I just worded it wrong my brain is a bit fried having just completed a couple of hundred pages of EICRs. @FatAlan

 

[DPG]

Appendix 15 shows one double socket is ok only. That is in 2.5, but I think if I came across that I would advise the client this is potentially hazardous, and in design terms fails on 433.1.1 although I could just about believe one double socket may not overload 6 sockets have a high potential to do so. Anyway if I was installing the circuit I would no way do it that way.

But the OP says it IS one double socket fed from the 2.5mm Daz

 

[7029 dave]

What do you mean what cable is the 4.0? It's bog standard 4mm+1.5mm cpc T&E. Length 1m. If someone adds another socket from the 2.5 in future, that's their look-out.

Yep, you could say the same, somebody could spur a spur off on RFC .

 

[The Ghost]

Yep just reread it and your right I think i'll hush up my mouth

 

[Wilko]

So - are we saying that a 5m spur in 2.5 protected by 32A mcb is ok?

 

[HandySparks]

So - are we saying that a 5m spur in 2.5 protected by 32A mcb is ok?

Yes, if there's only one accessory on the end of it.

Not something I'd install, but I wouldn't be rushing to change it either if found.