How to Find earth Break in ring main

[RF Lighting]

1.0mm cable is rated at 12a, would u put a lighting circuit on a 10a?

Yes

 

[sparkyspike]

Me too

 

[ELZ4742]

hang on a min here, did i not just say it was good practise? i didnt say it was wrong at all.

 

[ELZ4742]

1.0mm cable is rated at 12a, would u put a lighting circuit on a 10a?

Yes

really? thought that was wrong, fair enough. i admit defeat

 

[sparkyspike]

I take it your sparky must have disconnected the ring at the offending socket, otherwise both MCBs would feed the whole house, which you say isn't happening.

So if this is the case, he can tell you which is the last socket, n'est-ce pas?

 

[dingbat]

1.0mm cable is rated at 12a, would u put a lighting circuit on a 10a?

As I said, read Appendix 4... 1 sq mm T&E is rated at 16 Amps, ref method 1.

 

[ELZ4742]

1.0mm cable is rated at 12a, would u put a lighting circuit on a 10a?

As I said, read Appendix 4... 1 sq mm T&E is rated at 16 Amps, ref method 1.

then a question. why are houses generally on a 6 amp mcb?

 

[richardhill84]

I take it your sparky must have disconnected the ring at the offending socket, otherwise both MCBs would feed the whole house, which you say isn't happening.

So if this is the case, he can tell you which is the last socket, n'est-ce pas?

He never said that he'd disconnected the ring at a socket and i didn't see him do it, that's why i'm a bit confused. Maybe it was never a ring in the first place. I'll give him a ring once he sends me the completion certificate.

 

[dingbat]

[quote="ELZ4742]...then a question. why are houses generally on a 6 amp mcb?[/quote]

Because you don't choose the circuit breaker based on the cable, but based on the load, such that Ib <= In <= It. In a standard, three-bed house we usually have two lighting circuits and it is traditional to calculate at 100W per luminaire. So, upstairs, three beds plus bathroom, plus landing, plus loft = 600w. And 600/230 = 2.6 amps. Now, although some manufacturers do produce 3A MCBs the next one up is 6A... so that's what we tend to use.

Then we apply our correction factors, if any. And only then do we select a suitable cable... not the other way round. Like I said, Appendix 4...

 

[ELZ4742]

i see, thanks

 

[securespark]

To be fair to ELZ, the standard circuit arrangements in IEE's green book are 6A with 1.0mm² and 10A with 1.5mm².

 

[ELZ4742]

To be fair to ELZ, the standard circuit arrangements in IEE's green book are 6A with 1.0mm² and 10A with 1.5mm².

has this changed since yellow out of interest?

 

[securespark]

securespark: I don't want to leave it as is as just one radial is powering all sockets and it is only a 20Amp MCB. I could draw more than 20Amps if i have the lots of appliances on and trip it out.

Sorry. I thought he had correctly split the circuit into 2 radials, in which case this would be fine, given that my previous points are complied with.

You need to id the faulty leg and either:

replace it

or

disconnect it & make 2 x 20A radials.

 

[securespark]

To be fair to ELZ, the standard circuit arrangements in IEE's green book are 6A with 1.0mm² and 10A with 1.5mm².

has this changed since yellow out of interest?

Since yellow what?

I'm quoting from the IEE guide to the Building Regs.

 

[ELZ4742]

sorry, thought u were talking of the 16th ed elec regs having gone from green to yellow