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Immersion heater trips RCCB even when circuit is isolated.

Immersion heater trips RCCB even when circuit is isolated.


Old 11-16-12, 03:28 AM
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Question Immersion heater trips RCCB even when circuit is isolated.

My electrical knowledge is somewhat limited, perhaps someone could shed some light on the problem I'm having.

I've recently moved into a property where the state of the electrics are dubious at best. Basically, the landlord has one guy who does everything - gas, electrics, carpeting, decorating, etc and to be honest I wouldn't trust him to <insert your choice of simple task here>.

There's a combination of two problems which confuse me.

1) Electric trips off randomly, usually in the evening. RCCB on consumer unit switches off electric to whole property.
2) Switching on the immersion heater (switch downstairs, heater upstairs) trips the RCCB immediately.

If I turn of the trip switch for the immersion heater circuit to isolate the circuit then problem 1 doesn't seem to happen any more although it may still be a little soon to make that conclusion. Even with the trip switch for the immersion heater circuit turned off, problem 2 still happens.

Any tips, or an explanation on how what's happening is even possible would be much appreciated.
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Old 11-16-12, 04:12 AM
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Unfortunately........there probably is no easy fix.

Most likely it's a combination of mis-wiring and overloaded circuits.

Could be just at the limit.....then in the evening it reaches critical mass (cooking, washing etc.)

Not surprising though if the wallpaper guy has been dabbling with the electrics.

Also, how is it possible to turn the heater on when the "trip switch" is off?

Is the "trip switch" a double or single circuit breaker?.....is this in the UK?

Old 11-16-12, 04:19 AM
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Flicking the switch to turn on the immersion heater makes the RCCB switch off even though the trip switch (sorry, UK terminology, I believe you'd call it a single circuit breaker) for that circuit is turned off. That's what's confusing me, if that circuit is turned off at the consumer unit, how can flicking the immersion heaters switch do anything at all?

Also, forgot to mention. The random tripping started to occur before any appliances were even connected while we were still in the moving process so I doubt it's load related.

Last edited by kev51773; 11-16-12 at 04:35 AM.
Old 11-16-12, 07:13 AM
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Note: I have limited knowledge with Non-US wiring

An RCCB is the same as a GFCI device in the US. It constantly measures the imbalance between the two wires in a circuit. If the imbalance gets higher the set point, it trips. This has nothing to do with current, unless of course the circuit is overloaded in which case you would need to determine if it is a ground fault issue or an overload issue.

You have stated that it trips randomly so that would indicate that it could be a ground fault issue and not over-current issue. The best way to determine that is to use a clamp on meter to measure how much current is on the circuit.

If it truly is a ground fault issue, then you will need to find the source of the ground fault. I suspect the immersion heater is one.
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