Turning hot wtaer tap on causes RCD to trip?

[rubble2]

Trying to do some long distance diagnosis for an elderly relative (to determine if we need an electrician or a plumber)

The syptoms are that when they turn on the bathroom hot water tap the RCD trips in the consumer unit (not every time).

I can only assume that it is some connection with an instantaneous water heater (combi boiler ?) but they say that they have a hot water storage tank.

Also, it never trips if the kitchen tap is turned on.

Any thoughts please?

 

[bernardgreen]

If they do have a hot water tank and there is nothing switched on as a result of hot water being drawn off then the fault is going to be obscure.

Is it definately within a few seconds of when the tap is turned on or at sometime after hot water has been used ?


One cause may be a cable trapped between a copper hot water pipe to the bath room tap and something solid such as a joist. When the pipe heats up it expands and the expansion increases the pressure on the cable. It is possible that the pipe has damaged the cable and when expanded touches a live conductor.

If there is any plastic pipe involved with the bath tap then another possibility us that the change of water in the "insulated" pipe changes the conductivity along the pipe for a earth leakage path to be created. This would require a fault to exist somewhere where pipe work was not properly bonded to the electrical "earth".

If it is sometime after then possibly there is a leak from the bath or waste pipe that is allowing water to reach a light fitting or other part of the electrical system.

First thing is an electrician to determine which live or neutral at the CU is causing the RCD to trip.

 

[rubble2]

Thanks,

As I understand it, if it is going to trip than it trips immediately. The property is a bungalow so bathroom on ground floor.

I will try and get some better/more detailed information about how and when it happens.

 

[Taylortwocities]

It could be a pump or a valve in teh heating system.
If this is faulty then it may trip the RCD when the valve/ pump etc operates.

Look firstly around all of the heating bits and pieces and look for water leaks/seepage. After that its a detective job, as outlined above.

 

[rubble2]

It could be a pump or a valve in teh heating system.
If this is faulty then it may trip the RCD when the valve/ pump etc operates.

Look firstly around all of the heating bits and pieces and look for water leaks/seepage. After that its a detective job, as outlined above.

First prize.

Ended up going over there and noticed a noise like a motor running when the tap was turned on, thought at first it was water hammer but traced the source back to the airing cupboard.

When I looked inside, buried under a pile of towels was a pump - it was mad hot. Took all the clothes away and let it cool down seems to be running ok now, just told them to make sure there was enough room for air to circulate around the pump. - fingers crossed

 

[stem]

I came across a similar situation where there was a leak from the bathroom waste pipe that dripped into a light fitting in the room below, not enough to be visible from downstairs, but enough to wet the terminals.

OK this is a bungalow, so there won't be a room below, but does the waste pass above any electrical fittings or appliances?

With the above incident, using the cold tap on the same sink would also cause the leak and the RCD to trip.