zoning ring mains

[Delinquent]

I need to start planning the electrics for our extension but wondered if there are any regulations I should be aware of with regards to how you split a place into zones for separate ring mains.

Can I zone by rooms? So say have bed 1, bed 2, lounge, kitchen and hallways on ring 1 (the existing house as currently wired on a single ring), then bed 3, bed 4, dining and utility (the extension!) on ring 2? Really would rather not have to rip up all the flooring of the existing part of the house to split it any other way, I think it'd prove very expensive (when the wife posts the divorce papers...)

 

[BS3036]

No problem. In fact that's a good way to do it so that each ring can be on a different RCD. And the same with lighting, but the other way round. So (if you're using just 2 RCDs), a fault won't take out all the lights.

 

[ericmark]

Yes you can zone by rooms and when load is reduced due to using more circuits one may consider radials instead of rings although kitchen and utility rooms may still need rings due to load with washing machine kettles etc.
My sisters house is split side to side with two ring mains which gives more even load and less cable so the earth loop impedance reading are better.
My house has original ring then a second ring was fitted in alongside first.
But the problem can arise where detailed plans are not made as we tend to expect an up-stairs down-stairs split and if we are hunting for a fault it would be easy to isolate the wrong supply.
I have seen electricians tell owner their wiring is faulty when they could not verify a ring not realising it was a radial circuit and a 4mm radial split with extra sockets in 2.5mm added again where the electrician has assumed it was a ring. Yes we should not make those mistakes but they do happen.
My son yesterday was telling me about a list of faults he found on a test and most were due to the electrician jumping to conclusions rather than testing properly before he did work.
So if you depart from standard it is very important to document exactly what you have done.
That house holder was luck my son identified the problems and the electricians are no longer working for firm and it will be all corrected but we are all human and we will make mistakes.
We are seeing now the problems where part re-wires have been done and the lighting circuits have been split up and down stairs but the fact that two wire strappers on the stairs lighting was used has been missed resulting in borrowed neutrals which has been missed for years until the consumer units are changed and lighting circuits are put on different RCD supplies.
So do be very careful if you wire anything non standard even if it does comply with all regulations.
Eric

 

[Delinquent]

Thanks,

I was concerned about the ability to recognise the different rings, I think I'll make up a proper location plan and stick beside the consumer unit if I do go down the side by side rings route. I'd have preferred by-floor-zones just for neatness but just realised that would also involve ripping out a 1 year old bathroom that almost bankrupt me the first time...

My main concern though is Mr BCO being happy with my install. He's a top bloke and been ever so helpful but readily admits that wiring isn't his strong point. I've got to find the forms to submit to prove competence to fit it etc yet so didn't want to make a stupid mistake by submitting a plan that didn't meet current regs

I certainly know what you mean about electricians that haven't done the relevant tests before adapting a circuit - the existing place was professionally rewired some years before we bought it, then some additions made at a later date by a different pro... it was very interesting seeing how it had been done to say the least!