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Tripping shower - ? cause

Postby swayzak » Mon Feb 11, 2013 8:37 am


I have an old Showerforce 1000XM, connected to hot/cold feeds from the attic immediately above the bathroom.

There is white switch just next to the attic hatch labelled "Isolation", and has a small picture of a fan on it.

Occasionally (usually after sustained use), the shower trips the main blue fuse on the MCB.

The only way I can get electrics back on for the rest of the house is to turn the white isolation switch off, sometimes for 4 or 5 hours.

Then eventually I can turn the shower isolation switch on again & shower works.

Unfortunately the isolation switch appears to isolate all the loft electrics (light, mains sockets), so TV reception is lost as the aerial amplifier is located up there.

Any ideas what the problem could be & how to fix it ?

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Postby kbrownie » Tue Feb 12, 2013 7:45 pm

By main blue fuse do you mean the RCD?
The isolator with a fan on it, is for isolating extractor fans.
It seems someone has installed to isolate the loft and is not rated to be used on socket circuits, without being downfused first.
As it seems to happen when the shower is in use, I would conclude, that may be the pump is packing in.
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Postby ericmark » Tue Feb 12, 2013 9:16 pm

Can't find your shower listed but replacement says Power ratings: 230v AC@50Hz/3Amp/150W I would assume 3A inrush as 150W more like 1.2 amp.

I would assume blue = 16A as Wylex used blue to show that rating.

This does raise some questions as with standard ceiling roses the maximum size of supply fuse/MCB would be 5/6 amp not 15/16 amp as the ceiling rose is rated either 5 or 6 amp only.

Fan isolators are normally 6 or 10 amp rating which again raises overload questions.

The fitting of sockets on lighting circuits is not really compliant with "314 DIVISION OF INSTALLATION" in that "(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit" is not really complied with.

In real terms there should not be a problem but electricians now have to submit paperwork for what they do so breaking regulations could come back and bit them.

If it were my house I would install an array of fuses or switches so I could with ease isolate areas to find what was causing the problem. But for you much depends on what you are happy DIYing?

We clearly should tell you to get an electrician. But I fear the sharp intake of breath and jobs worth. And it really is jobs worth if an electrician loses his self cert status he may as well give up.

As already said most likely is the shower pump but question has to be how much are you willing to do as DIY?
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Postby swayzak » Wed Feb 13, 2013 9:24 am

Thanks both

I have ordered replacement shower ( ... -1000.html ) & an electrician is coming today to assess the situation / fit new shower if required.

The isolator switch now trips the blue mains RCD on MCB (if that is the correct terminology) every time I turn it on, so can't have attic/shower running at all.

Not sure why the previous installation wired that isolation switch to the whole attic - most annoying as the TV aerial amp is wired in up there, so no TV reception until this is fixed !

I will get the electrician to isolate the shower cubicle properly, and also look at wiring of the house to check for other anomalies. I suspect Billy Bodge has been at work in this house sometime previously ...
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Postby swayzak » Fri Feb 15, 2013 1:01 pm

It was the shower - replacement has cured the issue.

Thanks again for the advice.
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