Shower Nightmare Tripping RCBO - Replaceing With Thermostatic Running off Combi?


Postby Scottyboy99 » Sun Mar 29, 2015 7:03 pm

We recently had problems in our new house with frequent consumer unit tripping. Finding the culprit was a nightmare so we switched to an RCBO one to help find the offending circuit. Anyway all sorted but since then the electric shower trips the RCBO within seconds as it should do. It's because it's a 10.5 kW on a 16 amp breaker. God knows how it worked before as it was attached to a 16 amp MCB prior - it should of tripped but it always worked ! As I am sure the cable is not thick enough for the 10.5 shower and chasing walls out to fit 10mm is not something we can stomach I thought about replacing the shower with a thermostatic one run off the combi Boiler. Trouble is they are all 3 amp. I want to take advantage of the electrical feed that already exists. Am I asking for trouble getting the 3amp thermostatic wired into the existing combination which will be directly off the 16a RCBO?
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Postby proptech » Mon Mar 30, 2015 11:15 am

Hi Scottyboy99

Perhaps I'm misunderstanding, but a thermostatic shower off a combi shouldn't need any electrical supply at all. Exactly what type of shower have you been looking at ?
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Postby Scottyboy99 » Mon Mar 30, 2015 5:31 pm

I was looking at quite a few types on plumbworld site if my memory serves. Loads of them in the specifications said power supply 3A

Thanks
Wayne
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Postby Scottyboy99 » Mon Mar 30, 2015 8:18 pm

Sorry they are thermostatic power showers I've been looking at. I wonder if their requirement for 3A power supply can go on the electrical run already in place that has 16A RCBO at the consumer unit. There is one of those chord like pole switched already in the bathroom for the shower. I'm still baffled how the electric shower ever worked before without tripping the 16A MCB on the previous consumer unit!!!
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Postby proptech » Tue Mar 31, 2015 8:01 am

Thanks for the feedback. I think you are looking at the wrong type of shower. You do not need a power shower with a combi. All you need is a straight forward thermostatic mixer. Hot supply from the combi, and cold from the mains. Forget the electrics, you don't need any.
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Postby Scottyboy99 » Wed Apr 01, 2015 7:57 pm

Thank you so much. Yes I think what you say is best. I got in my head that if there is an electrical run there I must use it rather than waste but what you say makes sense. The electric unit we will replace already has cold feed so a plumber can utilise that meaning we just need a hot water feed from the combi. To be honest I think we will be best shot of the electric one. Anything that requires 45-50 amps in use frankly scares me, seems ridiculously excessive.

I don't suppose they do electric showers in the 3 kW-4kw variety do they?
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Postby proptech » Thu Apr 02, 2015 6:08 pm

Yes, all you need is the hot supply. You wouldn't get much water through a shower rated as low as 3-4 kw, in fact, just a dribble.
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Postby plumbbob » Fri Apr 03, 2015 11:49 am

I wouldn't even consider a replacement electric shower when a combi boiler is installed. Providing the boiler is reasonable new, say less than 15 years, and the cold water supply is adequate, even a modestly priced thermostatic mixer from somewhere like Screwfix will out perform the best 10.8kw electric.
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