Shower tripping mcb

[JohnW2]

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.

Agreed, but my thinking was that I would have thought that, in practice, a fault impedance anything like 100Ω would be incredibly unusual - far more likely to be no more than 'an ohm or two' or, at the other end of the spectrum, tens or hundreds of kΩ. With the 'common' low-impedance N-CPC or N-E faults, almost any real-world load on the circuits' would probably be enough for 30mA to go through the fault, and hence for the RCD to operate.

Kind Regards, John

 

[JohnW2]

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.

Yes, that moves the goalposts a fair bit - and makes Bernard's suggestion more of a possibility.

You can try to do your own detective work with appliances, in an attempt to find suspects - or, as you say, it might be time to get some skilled assistance. The possibility of something being amiss in the shower is, in itself, such a potential hazard (el;ectricity, water and naked bodies is a bad combination) that it would probably justify, or even warrant, a chekout by an electrician. The trouble with 'intermittent' problems is, of course, that Sod's Law makes it very likely (some would say inevitable!!) that everything will seem fine when examined, inspected and tested by an electrician!

Kind Regards, John

 

[JohnW2]

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