Electric shower trips the MCB

NickNickleby

Greetings,

In my usual kiss-up fashion, I'll start by saying I always come here for great advice and I've always been steered in the right direction, so thanks for that. And so to the current (pun intended) problem....

Son recently moved into 2nd hand house. Appears to have had some major work done around 2011, which included installation of Consumer Unit with MCBs to replace original wire fuses.

there's an electric shower fitted, datestamp 2017. It is on (I think) a 32A MCB.

When using the shower for any prolonged length of time, say > 15 minutes, the MCB trips. Nothing else affected. No RCB (or ELCB or whatever is being installed these days). When the unfortunate user dries of sufficently and goes down to the Consumer Unit , seeing the MCB tripped they flick it back on, return to the shower and can continue for another while - I have not determined if it will trip eventually after they get back in. They now expect the MCB to trip every time they get into the shower, but sometimes it doesn't.

So, some investigation suggests that limescale may have corroded the casing of the actual heater element, causing a short. Is it likely that such a condition could occur, whereby the short doesn't happen immediately power is applied? If we assume such a thing is likely, then I'll tell him to just get the whole shower replaced.

What about alternative problems? Could this be a dodgy MCB? It seems like a strange question, because I've had MCBs for yonks and never had a problem. I would hate to see him getting the shower replaced only for the problem to reoccur.

I'm popping over later to take the lid off the shower (with all the proper precautions of course) just to see if water is getting in anywhere. After that, assuming it all looks ok, we'll toss a coin to see if its: 1. Replace the shower, 2. Check the MCB and wiring to the shower (by a proper electrician).

as usual, comments welcome. If anyone thinks that tossing the coin should more than likely result in replacing the shower, based on experience, that's where we'll go - its my own preference.

Thanks in advance

John.G

If a 9kw shower then current draw is 39A so the 32A MCB will probably trip after ~ 15 minutes or so at 1.2 times its rated current.

Would suggest replacing with a 40A (B40) MCB.

I have a 40A RCBO on my 9kw shower. (Combined RCD&MCB as its fed directly).

If you do remove the shower cover, its power rating should be stamped on the heating can, also look at the voltage rating.

NickNickleby

Excellent advice JohnG thank you very much. I will go back and look at the rating of the shower (was already over there and saw no burning or water inside the shower casing).

So, get a lower rated shower, or increase the rating of the MCB.

Right, no point in replacing a likely fine shower. I'll tell son to get an electrician in.

Thanks again!

kirk.

As above Sounds like overload