Yes, you've told us that story before. I can't remember, did the B16 trip?
Kind Regards, John
B-curve vs C-curve
- Thread starter SimonH2
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Kind Regards, John
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Yes it did, bulb went short circuit, in theory there should be a fuse in the bulb, as most B22d bulb holders rated at 2A, however Ikea cheap rubbish did not have fuse in the CFL so it welded lamp to holder. An expensive cheap bulb.
That's what I thought I remembered.
That being the case, is it not very likely that the outcome (welding of the bulb to the socket) would have been exactly the same had the circuit been protected by a B6? The current would have been exactly the same in both cases and, although a B6 might have tripped slightly quicker than a B16 (hence slightly less energy dissipated), I rather doubt that the difference would have been enough to stop the welding happening.
Kind Regards, John
They must all be on good TN-C-S supplies.
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... or maybe even TT, in which case the only relevant loop impedance would be the same as it would be with TN-C-S
Are they ever good enough to allow C breakers on circuits with 400ms disconnection times?
Although TN-S earth's are 'only' meant/required to be <0.8Ω presumably there is no reason why they can't be much lower than that. As with TN-C-S earths, Ze can presumably be very low if one is very close to a transformer.
Yes, My Ze at home on a TN-S earth is 0.23Ω, which is good enough to allow for a C32 on the submain to the garage, in the hopes of providing discrimination with the B20s at the far end.
Yes, as I said, some people must be in that position, or even better. Are you fairly close to the transformer/
That might be wishful thinking even in relation to fault currents, let alone overload ones!
Kind Regards, John
I have a C32 MCB feeding the garage, which has it's own CU, containing B32 RCBO for sockets, B6 RCBO for lights and C32 RCBO for a Ceeform socket. I have an adapter in situ with a single 13amp socket on the end for this Ceeform.
The reason was that in previous places when various people (including me) have hooked up small site transformers, the MCB / RCBO has tripped, repeatedly.
The reason was that in previous places when various people (including me) have hooked up small site transformers, the MCB / RCBO has tripped, repeatedly.
Is the C32 in the house RCD-protected? If so, why the RCBOs (rather than just MCBs) in the garage? In fact, why even have B32 and C32 MCBs in the garage, given the up-front C32?
That's fair enough. As I said, if there is a good reason for having a C-curve device (and, of course, assuming that the Zs will support that), then that's very reasonable/necessary. What I was questioning was Simon's apparent suggestion that one should perhaps install C-curve ones 'just because one could' (i.e. Zs-wise), even when they were not really necessary. For reasons I discussed, I wouldn't personally regard that as very desirable.
Kind Regards, John
No, in the house it is not RCD protected (Full RCBO board bar this breaker), but runs down to the crawl space inside trunking, then lays loose on the ground until it gets to the garage, and is then trunked back into the garage CU.
The garage is all RCBO. I preferred that in the case of me using a spinning tool and a fault developing within the garage, hopefully either of the socket circuits would trip and leave the lights running. The idea of being in the dark with a spinning router or circular saw in my hands scares me.
Fair enough.
Fair enough, again. As you will realise, if the whole supply had been RCD-protected, there would have been little point in RCBOs in the garage and, indeed, not even any real point in having 32A MCBs in the garage (only the B6 really needed).
Extending those thoughts, I suppose you could have had an RCD instead of the two 32A RCBOs in the garage (and run both sockets circuits from that RCD), with just a B6 RCBO for the lights, but you would not have saved much, other than a few quid!
Kind Regards, John
About 20 or so terraced houses away.
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