Shower fault - Motor running without water when all MCB/RCD's off?

Supertoucher

Hi all,

Earlier this week we were woken up to the noise of our shower (power) coming on in the early hours of the morning. The noise was the sound of the motor but strangely no water was coming out. The shower was already obviously turned off at the button when the fault happened and the motor continued to run to the point it started to exhibit a electrical burning smell. I turned off the MCB labelled for the shower (although there is also an electric shower upstairs so it might not be the same one) and the motor still continued to run. I then proceeded to turn off every MCB and RCD in the consumer unit and the shower motor was STILL running. Only when did I turn off the main switch for the whole house did the motor cease to run.

Since then an electrician isolated the shower and is due to come back next week but was only in quickly due to other duties.

It has given me concerns about the safety of the wiring in the house which is private built dwelling (I.e. not an house in a collective estate built in 2000). We are the second owners. In my mind, the MCB/RCD if not being tripped by a clear fault (at least in terms of operation), surely one should have been able to turn off/isolate the shower?

It has however, left me wondering in the interim how this could happen, both in terms of the shower motor coming on, on it's own, when the switch was off, with no water coming out and also, why no MCB/RCD turned it off and only the main switch did? Could anyone please explain it, if little else to satisfy my curiosity?

Thanks in advance.

meercat

Have you 2 electric showers

perhaps there’s a priority switch fitted somewhere (in your attic)and there’s a contactor gone faulty

you shouldn’t get a burning smell from anywhere so this needs to be investigated asap

Supertoucher

Thanks for your response. We do have two showers, however one is an electric shower (Triton T90SI) and this one (faulty) is a power shower (Triton AS2000XT). I may be mistaken but I thought priority units were for only if you had two electric showers due to the potential simultaneous current draw. I thought power showers had a much less current draw because they don't heat the water?

Lenar3556

https://www.boards.ie/discussion/comment/121115654#Comment_121115654

Your understanding is correct.

The middle of the night start up is probably down to a faulty switch within the shower. The water flow is controlled separately by a mechanical valve, hence the motor running but no flow. The burning smell was possibly caused by the pump been driven against a dead head / no flow.

An MCB or RCD wouldn’t be expected to trip in the case of the above, it’s just that fault is outside their capacity.

Tripping all MCB’s and the thing keeps going could be more serious and it needs to be investigated by your electrical contractor.

kirk.

Sounds like shower isolator was left on and power shower developed a fault

After that you didn't locate the correct tripswitch or didn't turn it off

You're correct u don't need priority units for those 2

Sleeper12

The AS2000XT is now obsolete. Couldn't be certain without being there to test it out myself but most likely a faulty pcb board in the shower. Not sure if this part is still available. If not then the triton novel SR silent running thermostatic power shower is the replacement for the as2000xt

Supertoucher

https://www.boards.ie/discussion/comment/121116157#Comment_121116157

Thanks but i'm 100% certain I turned every MCB/RCD off. As the MCB labelled shower didnt turn it off, I went through them 1 by 1 from most relevant to least and only did the main switch as it was the only one left.

https://www.boards.ie/discussion/comment/121116404#Comment_121116404

Yep the AS2000XT was on our list to replace anyway due to the noise. No doubt the shower developed a fault but the main puzzle is how the motor continued to be powered despite turning all MCB/RCD's off.

Supertoucher

https://www.boards.ie/discussion/comment/121116148#Comment_121116148

Thanks for your post, that certainly makes sense regarding the valve etc and the motor. Much appreciated!

Sleeper12

It can't run without 230V going to it. If wired correctly it will be on its own trip switch or on the immersion. It shouldn't be on the socket or light circuit. I would suggest getting a REC to make sure that It is wired correctly before replacing the shower

kirk.

Ya he'll need to establish why he couldn't switch off at the board

A sub board somewhere else would explain it

meercat

thank for the additional information

a sub board may be likely (although this should have a dedicated mcb and not be connected to your main switch)

otherwise it’s incorrectly wired

you need to get it checked (and perhaps the whole installation) by a rec.

kirk.

https://www.boards.ie/discussion/comment/121117056#Comment_121117056

Sub-board would be connected through "main switch"

Probably something else anyhow

meercat

https://www.boards.ie/discussion/comment/121117340#Comment_121117340

It shouldn’t be connected directly to the main switch ,it should have separate protection for the cable feeding the sub board

kirk.

https://www.boards.ie/discussion/comment/121120109#Comment_121120109

Have u now i thought u were saying the main switch wouldn't turn it off

Edit: 😁 forgot switching everything except the main switch would likely have cut power to a sub board