Shower Pump tripping RCD

HI All,

Re-fitted bathroom december 2007 and fitted a salamander CT50 pump for the shower.

Last summer had new consumer unit fitted as the old one was wired fuses.

A month or so ago, whilst taking a shower the RCD tripped all the sockets, the shower is not on this circuit. It has continued to do this intermittently, i.e. not every time we take a shower, however it only happens when we take a shower.

I've had the elecrician out a couple of times, did some test and replaced the RCD, however he did say he didn't think this was the problem.

Shower tripped again after a couple of days, came back out and fitted a new RCD thing with its own neutral, this wouldn't even go in.

Checked the wiring to the shower pump which was fine but did find some crushed / nicked cables in the spur in the airing cupboard (which the pump is run from) and replaced these and tidied everything up.

A day later and it's happened again.

Now, it doesn't trip as soon as the shower is turned on or when it's turned off, it does it sometime in the middle.

Do you think this is a fault with the pump?

Please remember this is guess work but the more current that is used the higher the voltage differential between neutral and earth and there for the more likely a neutral / earth fault will trip the system.

I would guess the fault may have nothing to do with shower except that it is drawing current and so allowing the fault to trip the RCD.

Fault finding with anything which has a timed sequence is a problem. Washing Machines, Fridge/freezers especially if they have auto de-frost, Tumble dryers, Dish washers all include timers and may only trip an RCD at a certain point in the cycle. Even central heating can cause hard to find problems where the temperature has to be above or below a critical figure before the fault shows itself.

With the shower you are using it will cause the heating to also switch on and any fault with domestic water heating could show itself when the shower is used especially where a neutral / earth fault and with just domestic water there is not enough current draw to trip the system.

It is unlikely that as the house holder you will find the fault although turning items like domestic water off while using the shower (for test only of course not suggesting you take cold showers) may help pin point where the fault is. But it is really a job for electrician and if he can't pin point then only option is to replace the RCD and MCB's with Isolator and RCBO's. Meters able to monitor earth leakage are available but expensive and I have not got one which may mean you need an electrician who does have monitoring equipment.

As well as investigating earth leakage, consider the possibility of a water one.

The symptoms you describe could be perfectly explained by water getting into a socket or light switch somewhere - i.e. it takes a bit of time for a small leak to get there, it may not get there depending on who is in the shower, how fierce they have it, where they point it etc (assuming it's not a fixed head).

Don't give up on the other stuff, but OOI try running the shower, if you can, with the shower head removed and water going directly into the drain, i.e. not against the walls at all.

Thanks for the replies.

The water only comes on at specific times so I doubt it could be this. Have checked for leaks an there are none.

The shower pump is on a feed that is only shared by the emmersion heater, but thats not used.

I bet it is a leak

mdj1 said:

The water only comes on at specific times so I doubt it could be this.

Click to expand...

Surely the water comes on at the exact time the shower is used?

And at a varying time after the shower starts to flow, something causes an RCD trip.

Has the RCD ever tripped when the shower is not being used or has not been used for a few hours?

Of course the tank fills up when we use the shower, but thats gravity fed, the water only heats up twice a day.

The RCD has never tripped other than when the shower is running.

I very much doubt that it's a leak outside the pump as everything is dry and the tiles / bottom of the bath we're double sealed.

I have actually replaced the pump this evening as Salamanders come with a 2 year warantee.

Had a shower with the new pump and all was ok, but only time will tell.

Will keep you updated.

I plump for the pump!

Sorry - did you say you like pumping plumpers?

Yes, but that's not important right now (to quote "Airplane!")...