Immersion heater on 32A breaker
- Thread starter Rad1o
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You could, since the breaker is really only there to protect the cable, not what it's supplying. However, it follows that you would have to use cable much bigger than would be necessary with a 16A or 20A breaker - with a 32A breaker, the cable would have to be at least 4 mm² (maybe 6 mm², depending on how it was installed), whereas 1.5 mm² (maybe even 1.0 mm², given recent changes in regs) might be adequate with a 16A breaker.
Kind Regards, John
Only if it supplies no more than one double socket - hence, at worse, with the downstream protection of 2 x 13A fuses
See above - IF you consider that overload protection is necessary.
However, I accept that a good few people would say that an immersion heater is (very) unlikley to result in an overload, in which case overload protection might not be needed at all. Hence, 1.0 mm² (Method C) cable would then be acceptable with any MCB which provided adequate fault protection. I haven't done the sums, but I would suspect that a 32A MCB may well be OK, maybe even one of higher rating.
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3 meter limit and no branch and a BS1363 device.
You've been repeatedly told that the "3 metre limit" of 433.2.2 ONLY applies if there is not adequate fault protection - and I can't really see how the situation could be compliant if the fault protection were not adequate ...
Maybe for that reason, I've never heard of a suggestion that an unfused spur from a ring final can't be longer than 3m, have you?433.2.2 of BS7671 said:
... and, as for 'no branch', an unfused spur from a ring final obviously cannot have any 'branches', since it is only allowed to supply one thing.
Kind Regards, John
Can we rewind to the beginning.
You are basically creating a new circuit.
Firstly, this needs notifying to the local authority. If you are doing it your self, you need to raise a building notice before you start work (costs £££). When you have finished you'll need to fully test and certify the new circuit (do you have the necerssary calibrated test equipment? It easier and cheaper to use a registered electrician to do the work.
Assuming you are able to do this as a DIY project,
looking at the CU.
The STANDARD domestic radial circuit arrangements are
2.5mm twin and earth protected by a 20amp MCB or
4mm T&E protected by a 32A MCB
As you are a DIYer, I encourage you to stay within these guidelines. (If I found a 2.5mm radial on a 32A MCB during an inspection it would be an unsatisfactory conclusion).
Quite honestly, MCBs are so cheap, why risk putting a cable that has (when installed in ideal conditions) a maximum current-carrying capacity of 27amps on a breaker that is too big for the job? Use a 20, or 16amp MCB.
Your new circuit must be RCD-protected. are your spare MCB positions in an RCD-protected part of the CU?
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