Power Shower - RCD Tripping

[speed12]

Hi All,

I am looking for some advice with an issue that we currently have.

We originally had a Mira Power shower when we moved into the house, the shower is connteced to the mains via an RCD spur on the landing. No isolation switch was present. Anyway about 6 months ago the RCD started to trip, sometimes during a shower and sometimes when the shower was not in use.

Recently its been so bad that I bought a new Mira Power shower (same footprint, same connections etc). I fitted it yesterday and replaced all existing wiring with 2.5mm2 cable (the manual said at least 1.5mm2 was needed). I put in a new wire to a ceiling mounted isolation switch too as this was missing on the original shower.

Checked all connections, checked for leaks all ok. Wired up RCD last night and flicked the power back on. Everyting worked fine. However I woke up this morning and found the RCD had tripped during the night despite the shower being isolated.

Had a shower this morning no problem, Just checked and again the RCD has tripped during the day (again the shower is isolated).

So my thoughts are now turning to the RCD itself being faulty? its tripped so many times this past 6 months that perhaps its now past its best? I coudl check all wiring again but I only did tht yesterday and am pretty sure its all ok.

The only think I have not done in accordance with the Mira instructions is to fit a double pole isolator with 3A fuse. I could not find an isolator with a 3A fuse whereever I looked! so am relying on the fuse in the RCD doing its job.

Anyone got any advice before I call in an Electrician to do some resistance testing?

Thanks

 

[Taylortwocities]

Your RCD spur is your isolator! That is where the 3A fuse should go.

No idea re what is causing the tripping. It could be anything, it could be the RCD spur that is faulty……(is it a Powerbreaker make BTW?)

I'm afraid you need someone with the correct test equipment to check wiring and the RCD's operation.

 

[speed12]

Thanks

I'm aware that the rcd is an isolator however I was merely following instructions which suggested a desperate ceiling mounted isolator, I see no harm in having this as an additional means of isolating the shower.

I've just ordered a replacement RCD. The existing one is a timeguard. I've bought the same model and its got a 5 year warranty. I figured for £25 I may as well try fitting a new one, then everything in the shower circuit is new.

If that doesn't work then I will admit defeat and get a sparky in. I'm thinking of having a new consumer unit fitted anyway.

 

[ericmark]

Not quite sure what you have but will try with a few pointers.

1) A fused connection unit (FCU) which is an isolator can take 1, 2, 3, 5, 7, 10 or 13 amp fuses they are all same size so it should be simple to swap a 13 for a 3 amp.

2) A RCD has no overload built in. You can get a RCBO which is a RCD and MCB combined and also a RCD FCU with is a fuse and RCD combined but a standard RCD has no overload.

3) Not all switches are isolators often the neutral is not switched and a neutral earth fault can cause a RCD to trip.

4) If the RCD supplies more than one item often an earth - neutral fault on one item can cause the RCD to trip when another item is used.

So what does the RCD supply?

 

[ericmark]

From your reply it would seem you are using a RCD FCU and there are two different types.

A passive RCD will remain on even if there is a power cut. But in some odd situations the volt drop can mean these will not operate as intended under fault conditions.

The active RCD however trips when every there is a power cut so fails save.

If you have an active type and there are even brown outs over night it could trip even with no fault.

 

[JohnW2]

I've just ordered a replacement RCD. The existing one is a timeguard. I've bought the same model and its got a 5 year warranty. I figured for £25 I may as well try fitting a new one, then everything in the shower circuit is new.

From what you've told us, I think it quite likely that a new RCD may solve the problem - if it doesn't, as you say, it will be time to summon an electrician!

Kind Regards, John