MCB tripping

[Greasybone]

I've recently been having trouble with my immersion hot water system, we have three switches, one serves the pump into the hot water tank, the other two serve the heating elements (one on the top and one on the side of the tank).

The circuit breaker for the hot water system started tripping off several weeks ago but only very occasionally. Now it's tripping more frequently. I tried changing the switches for new and I changed the thermostats in the immersion elements (as they're fairly easy to do).

I noticed last night that the circuit breaker tripped off even when all the switches were turned off. I even disconnected the wiring from the immersion elements and the same thing happens. So I've established that the fault doesn't lie with the elements, is this likely to be a wiring issue - perhaps a faulty earth?

 

[EFLImpudence]

Is it an RCCB. RCBO or MCB that is tripping?

 

[Greasybone]

It's an MCB

 

[EFLImpudence]

In that case it must be caused by an overload or a short circuit.

Overload is unlikely if switched off and disconnected - is there anything else on the circuit?

Short circuit is a live wire touching the neutral or CPC(earth wire) or something else which is earthed.

So - it would seem to be a 'wring fault'.

It has been known for cables to get worn under a floorboard and trip when stood on.

When you say 'pump into the hot water tank', does this include a central heating system?

 

[Greasybone]

Hi,

The pump into the hot water tank only serves the immersion heater. But interestingly enough the heating system does share the same circuit.

It's a 'warm air heating system' which was installed when the flat was built in 1970. My girlfriend owns this flat and when she first moved in four years ago she said the heating system used to trip the MCB so she hasn't used it (or investigated the fault). The heating system is never switched on and she uses electric radiators instead.

 

[PrenticeBoyofDerry]

So are you now trying to use the heating system again and the fault (which has not been resolved) is still tripping the MCB or is this an unrelated fault on a different circuit.
If the former, I would be investigating the pump.