And why not?
Many on here keep stating a 4mm² spur is suitable to take the full 32A load... What's the difference?
How about a parrallel fed 2x 2.5mm² for a 32A cooker circuit?
EDIT; Too slow.
Extending ring main and lighting in to new extension
- Thread starter If in doubt...
- Start date
Many on here keep stating a 4mm² spur is suitable to take the full 32A load... What's the difference?
How about a parrallel fed 2x 2.5mm² for a 32A cooker circuit?
EDIT; Too slow.
Sponsored Links
Too slow
You tell me - if you have never done it.
My answer would be there is no point.
Using cables that have a CCC less than the rating of the OPD is not necessary.
There are regulations governing cables in parallel.
There is no point doing it if not necessary.
I have most certainly loaded 2.5mm² ring circuits right up to the 32A limit at a single point. It's a very common occurance in public entertainment. In fact I'll go further and claim to have fully loaded 40A 2.5mm² ring circuits at a single point.
That wasn't relevant to the question, however 'no point' is not a reason not to do it.
I have known it in new build where first fix cocked up.
Again not relevant to the question, however it is in the regs as a suitable design.
There are and I have conformed to those regs on a fairly regular basis. The regs are very handy.
Is doesn't have to be necessary to be a good way of doing it.
Sponsored Links
Sory John I claimed that first.Too slow
Unless I missed it, I don't think your claim was there when I posted mine
Kind Regards, John
I'll make the same claim but I'll not fall out over it.Unless I missed it, I don't think your claim was there when I posted mine
Kind Regards, John
Ok. You win. I can't compete with that.
I know it's way outside of DIY/domestic etc but I've lost count of the times I've bunched multiple cables to get a temporary feed for stage lighting, heating, etc.
That's nothing to do with what was being discussed.
Do we any longer need a special category of circuit so we can use a 27A cable with a 32A OPD?
Actually, as you well know, the stipulation is a 20A cable but you mustn't use that one; instead use the next size up.
I do realise that it could hardly be banned because obviously it is safe - but is there really any point?
Or to put it another way if you really like rings, why is only the one configuration of ring circuit allowed?
Why not a 4mm² ring with 63A OPD?
Do we any longer need a special category of circuit so we can use a 27A cable with a 32A OPD?
Actually, as you well know, the stipulation is a 20A cable but you mustn't use that one; instead use the next size up.
I do realise that it could hardly be banned because obviously it is safe - but is there really any point?
Or to put it another way if you really like rings, why is only the one configuration of ring circuit allowed?
Why not a 4mm² ring with 63A OPD?
We clearly don't 'need' it - i.e. we could certainly manage without it.
Quite so- and I don't think anyone has ever come up with a reasonable theory as to why we "mustn't use it".,
Good question. There are probably some circuit layouts which enable a ring to be installed which uses a little less copper than would radials(s). In comparison with 20A radials, it will usually mean half as many OPDs. Then, as I wrote earlier, it does provide 'CPC redundancy'. However, as I also said, there are also downsides.
To be the same 'ratio' (OPD/CCC = 32/20) as with a 20A CCC cable, it would presumably have to be no greater than a 50A OPD [ 37 x (32/20) = 59.2 ] (or maybe lower if, as to mirror the situation with 2.5mm², a CCC <32A were allowed) but, yes, that would seem logically consistent.
Given that ring finals were (I presume) introduced primarily with domestic installations in mind, I would imagine that (certainly then, and probably still now), if it ever were considered, it could well have been decided that there would be little call for a 50A sockets circuit in a domestic installation?
Kind Regards, John
Edit: numerical errors corrected
Last edited:
Shouldn't you be using 37A - CCC of 4mm².
That still doesn't result in 63A, though.
I thought the criterion was 60% of the OPD rating.
32 x 0.6 = 19.2A
63 x 0.6 = 37.8A - albeit just over but I was just making the point.
There is also the fact that 2.5mm² rings could have a 40A MCB - 40 x 0.6 = 24A
Who says only one format is permitted, the regs list only one but that doesn't mean others are forbidden.
Biggest I've worked on was 120mm² 4C SWA on 300A fuses.
Actually we inherited them from the maritime environment.
My understanding is that the standard 32A ring with cable that has a current rating of at least 20 amps and a size of at least 2.5mm² (1.5mm²) is "deemed to" comply with the requirements for overcurrent protection.
I would assume that for any other ring you would have to justify the incomplete overcurrent protection some other way.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
