Power shower tripping circuit breaker

[pramsay13]

We've been in our house for around 7 years now. In the en suite there is one of these fancy bath / shower / jacuzzi / side jets / radio / lights monstrosities that we inherited.
Recently the shower has started tripping the circuit breaker. It started doing it after a long shower, working its way down to just after a few minutes.
Something like this happened in a previous flat, and the circuit breaker wasn't rated high enough so it had to be changed.
Do I need to get a spark out to have a look, or can I check using a multimeter to see what breaker I should be using.

 

[EFLImpudence]

If it is an RCCB or RCBO that trips this is not relevant.

Do you know the rating of the shower and the MCB?

It is possible that if MCB is underrated it has been overheating and has become 'weak' but just fitting a higher rated one should not be done until the capacity and routing of the cable is determined.

 

[Porque223]

working its way down to just after a few minutes

Increasing cable insulation leakage current due to a water leak is tripping your RCD in less and less time?

 

[ericmark]

I will guess not a power shower and the MCB was originally too small for the shower and it has over time become stressed so it is becoming more and more sensitive.

It was common in the early days to fit 7kW showers which could run from a 32 A MCB. It is also common for these to get changed for a higher wattage but the 32 A MCB has to remain as it protects the cable so without changing the cable the only thing which can be done is renew the MCB for one of same wattage and either take short showers or change the shower back to a low wattage type.

A power shower does not heat the water and is just a pump with these the MCB is more like 6 A and tripping could be caused by a faulty motor. Seem to remember it's a brushed motor on the few I have worked on so the carbon from the brushes could be causing a problem. It would require a service to clean out carbon and if required change brushes.

Also the motor may be damaged are require replacement if one winding goes down it will cause it to spark a lot which in turn may trip the RCD.

Maybe you can tell us size of the device which trips and say if MCB or RCD or RCBO that is tripping?

 

[pramsay13]

Hi all, sorry for the delay with answers. We've just had a new baby so hardly got time for taking a shower never mind sorting this stuff out.
The shower is a power shower, water is heated by the boiler in the kitchen and stored in the loft until needed.
I've attached pictures of what I think is relevant (//www.diynot.com/network/pramsay13/albums/16783)

Pump is 4A 850W
MCB is MK5906s which is 6A.
Cable is 10mm wide (excuse the rule)
I can easily change MCB or even cable as everything is easy enough to get to.

Cheers[/url]

 

[Spark123]

Yes it appears to be a power shower, at a guess it will be the pump which is the problem but nothing is 100% sure without getting in there with a clamp meter.
Maybe worthwhile getting a friendly electrician in to clamp the supply?

You should also have a blank in the right hand side of the consumer unit so you can't stick your fingers in!

 

[pramsay13]

I've tried a few friendly electricians but no-one seems to want my money.
Any pointers for having a look myself?

 

[EFLImpudence]

Just a thought -

Have you added anything to the circuit recently?

 

[pramsay13]

Nope nothing. When I was up taking photos last weekend I flicked the switch and the pump is still working. This seems to be what happens but it will trip in another week or so.

 

[JohnW2]

Pump is 4A 850W
MCB is MK5906s which is 6A.

I would have thought that a 6A Type B (which is what you have) MCB might be a bit marginal. It would be fine whilst running, but the 'start up current' might be enough to trip the MCB (I presume that it 'switches itself on and off' during use?). The pump indicates a 5A fuse, but fuses are more resiliant to brief overcurerent than are MCBs, particularly ('the usual') Type B ones. That could possibly be the problem.

Cable is 10mm wide (excuse the rule)
I can easily change MCB or even cable as everything is easy enough to get to.

I think you really do need an electrician. Increasing the rating of the MCB (or maybe changing it to a different 'type' of 6A one) might be an answer, but it looks as if that cable might well not be large enough for an MCB rated more than 6A. An electrician could look into all of that, as well as looking to see if there is any other explanation for your problem.

Kind Regards, John.