I would strongly advise against somebody who doesn't know the difference between an RCD and an MCB taking the cover off the CU, I also doubt there is anything wrong with the wiring inside the CU, and if it is, that's a job for a spark anyway
Shower tripping mcb
- Thread starter GiganticDays
- Start date
I would strongly advise against somebody who doesn't know the difference between an RCD and an MCB taking the cover off the CU, I also doubt there is anything wrong with the wiring inside the CU, and if it is, that's a job for a spark anyway
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Scoby_Beasley
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Stranger Danger is real mind you!
You have sent me a PM but I can't reply as we're not "friends". Looks like you'll need to allow messages from people who aren't friends to get a reply.
Stranger Danger is real mind you!
It's in "message settings"
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Doh! It would be wouldn't it!!
Dufoss!!!
Dufoss!!!
Could you expand on that, i.e. what a Live-Neutral imbalance is, in the context of a loose connection, how it gets created and where the balance of the current goes, and how/why?
OK I had a shower tonight and all was fine. Mrs GiganticDays had one (longer and probably hotter than mine) and it tripped twice.
Bugger!
Think I need someone to check it out.
Bugger!
Think I need someone to check it out.
"If there is a difference between the electrical flow in on the live line and out on the neutral line something is wrong; the electricity is (presumably) flowing out of the circuit somewhere, but where?"
Loose connection increasing resistance through, well, being loose, becoming corroded (coated). Folks always tighten the live, but only tighten the neutral. Mostly loose neutrals in c.u's etc. cause the burning out/start the fires, unless of course the rcd/mcb gear is faulty to start with.
There's no "presumably" about it, even in red
Electrical current cannot disappear. If there is a difference between the L and N current, then the difference must have gone somewhere - hence BAS's question..All quite true - but, again, irrelevant to the creation of L-N current imbalances. If the neutral connection(s) are loose and 'high resistance', L and N currents will still be identical (maybe measurably a little lower than without the loose connection), unless there is some leakage 'to somehere else' from somewhere in the circuit - hence, again, BAS's question.
Kind Regards, John
There's no "presumably" about it, even in red
All quite true - but, again, irrelevant to the creation of L-N current imbalances. If the neutral connection(s) are loose and 'high resistance', L and N currents will still be identical (maybe measurably a little lower than without the loose connection), unless there is some leakage 'to somehere else' from somewhere in the circuit - hence, again, BAS's question.
Kind Regards, John
Yea, talking out me Harris. I blame the beer.
It may not be a fault in the shower circuit, it may be Neutral to CPC ( or ground ) fault on another circuit that is diverting current from the neutral bar and away from the RCD's sense coil.
Whilst, as we've often discussed, that is a phenomenon which does occur, I would have thought it unlikely to be the explanation in the OP's case. If there were an even vaguely low-impedance N-CPC or N-E fault on one of the circuits served by the RCD, then one would expect the RCD to trip if there were any appreciable current in any of the circuits served by that RCD - but the OP reports tripping only in relation to shower use.
The only situation in which I could think of this being the explanation would be if there were a high-impedance N-CPC or N-E fault in one of the other circuits, such that leakage via that path was only adequate to trip the RCD if one of the circuits had a very high load - and the shower might be the only load large enough to do that. In any event, an IR test of all circuits served by the RCD would answer the question easily.
However, 'common things are common', so if trips occur consistently in association with shower use, then I think that the first suspect has got to be the shower (or possibly shower circuit).
Kind Regards, John
If the fault impedance is say 100 ohms and the impedance of the neutral conductor through the RCD (*) is 1 ohm then the load current has to be 100 times the 30 mAmp RCD trip current. In this case a load current of 3 amps will result in a trip. (3.03 to be precise )
In reality the impedance through the RCD is often less than 0.1 ohm requiring a load current in excess of 30 amps before the RCD will trip.
(*) from neutral bar to the point where CPC joins neutral at the cut out
In reality the impedance through the RCD is often less than 0.1 ohm requiring a load current in excess of 30 amps before the RCD will trip.
(*) from neutral bar to the point where CPC joins neutral at the cut out
There's been a development in that we experienced a trip without the shower being in use today.
Best get a spark in I guess.
Best get a spark in I guess.
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Try unplugging all appliances. Switch off those that don't have a plug, like boiler, immersion, cooker etcetera.
Then see how long you go without a trip.
Obviously, if you need the appliances, plug them in / switch them on and use them. When you've finished, unplug or switch them off again.
Then see how long you go without a trip.
Obviously, if you need the appliances, plug them in / switch them on and use them. When you've finished, unplug or switch them off again.
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