Electric shower switching off trips RCD and the shower MCB as well as the ring main

[manic26]

Hi all, this is my first post I think although being a lurker for a while. I wonder if anyone has experience of something like this and a possible solution:

The electric shower when switched off trips the RCD. It will keep tripping until the ring main MCB is brought down. Which then cannot be switched back on (as it trips the RCD again and again) until after about an hour.

Looked inside the shower as well as the pull chord switch nothing dodgy, burnt out or loose cable everything looks in order. Now I cannot understand how is this ring main MCB playing up in conjunction with the shower circuit?

 

[Iggifer]

Is the ring final MCB next to the shower MCB?

 

[scousespark]

You need to get an electrician to check the circuits as an mcb tripping indicates a fault.
This is not something you can solve in thread here.

 

[manic26]

Is the ring final MCB next to the shower MCB?

Yes it’s right next to it and both are 32amps

 

[Iggifer]

And what kW rating is your shower?

 

[scousespark]

Seriously, you need an electrician who has the knowlefge and test equipment required to check your installation. It's far from normal for an RCD to operate and then be affected by a different circuit.

 

[flameport]

Now I cannot understand how is this ring main MCB playing up in conjunction with the shower circuit?

Shower MCB is overheating, probably because the shower uses more than 32A. The heat causes the ring MCB to trip as well. The RCD trip may be related or may be a separate fault.

At the very least, the shower circuit requires testing, both of the MCBs need to be replaced, the shower one with the correct value, although that also depends on the size of the cable and how it has been installed - if that is unsuitable for the larger MCB then it's rewire or replace the shower with a lower rated one.

 

[WhydidIstart]

It is probably as suggested above, however I'm wondering if it is heat, why the trip on switch off and not just after several minutes of use?

If your ring main had something (or things) 'leaky' that are sending several mA to earth, that may not be enough to trip the RCD. Your shower may have a fault where perhaps steam is getting in and causing the switch to leak several mA to earth. In combination with your ring main leakage this now causes the RCD to trip, however without this 'extra' leakage, it's not enough to trip the RCD?

I had a similar problem in a house with the old style large seperate RCD feeding the whole installation. I got spurious trips but couldn't find any particular device or circuit at fault.

A few mA from an inverter microwave, another few mA from an oven, another few from washing machines, another few from computer switch mode power supplies all added up to enough to sometimes trip the RCD. I now have all RCBOs (so individual RCD protection on each circuit) and no problems since.

If your shower is more than about 7kw that is a problem though as it's overloading your 32A MCB.

 

[ban-all-sheds]

The electric shower when switched off trips the RCD. It will keep tripping until the ring main MCB is brought down. Which then cannot be switched back on (as it trips the RCD again and again) until after about an hour.

Has it always done this?