Advice needed re Triton Zante Electric Shower tripping MCB

[dirty harry]

I was working at a customer's house yesterday (doing plumbing not electrics) when the customer asked if I would look at their Triton shower that was playing up. A year after it's installation, it has started tripping the MCB, but with a loud bang too, not just a simple trip!

Apparently, the electrician that fitted the shower replaced the old single ceramic fuse (which was actually a nail!!) with a 40A MCB, still retaining the old single fuse box itself (I noticed the on/off switch on the fuse box is blackened too). From here, a 10mm cable goes out of the wall, alongside the external wall (no conduit to protect it) and into the roof void, before going back directly into the shower itself. There is no isolating pull-cord switch in between the fusebox and the shower and there's no sign of water getting into the unit.

I've been back today and the customer flicked the MCB back on and the shower started working again, however, within 5 minutes the MCB went "bang" again and it's back to square one - no shower.

I can't understand why it would start tripping out a year after installation so I wondered if anyone here as any clues. It's a Triton Zante 9.5kW shower if it helps. She has mentioned that the shower occasionally goes really cold, then really hot, so could that be associated with the problem?

Cheers

 

[LoveRocket]

What goes BANG - that shower or the MCB?

 

[dirty harry]

The MCB.

 

[bongos]

From your description it sounds like a fusebox with rewirable fuses so I'm guessing the shower is not on an RCD? Or does it have a separate RCD enclosure?

I wonder if there was previously a problem here hence the nail in the fuse carrier? A high impedance short of some variety might cause the MCB to trip once the it had warmed up nicely...

 

[dirty harry]

From your description it sounds like a fusebox with rewirable fuses so I'm guessing the shower is not on an RCD? Or does it have a separate RCD enclosure?


I wonder if there was previously a problem here hence the nail in the fuse carrier? A high impedance short of some variety might cause the MCB to trip once the it had warmed up nicely...

It is an old, single "rewireable style" fuse box which has had a modern 40A MCB stuck in it! There is no RCD enclosure that I see of.

I guess there may well have been a problem with the box, as you say the fact there used to be a nail in the fuse carrier could be a hint!

Anyone else have any ideas? Would it be worth swapping the old fuse box for a modern shower consumer unit?

 

[dirty harry]

Has anyone got an suggestions at all? PLEASE!

 

[LoveRocket]

I think the shower is goosed, mate.

Does the shower still flow water with no power? (Turn it on, then switch of the isolator or MCB and see if the water still flows)

Have you got an insulation resistance tester? There could be a fault on the cable, but it's far more likely to be the shower.

 

[dirty harry]

Thanks for the tip, must admit I was beginning to suspect the shower and I think you may have confirmed it. Haven't checked to see if there's any flow without power but can do it tomorrow.

Cheers.

 

[bongos]

It could be the shower, it could be the cable. Or something else maybe.

What power is the shower rated at? Are you sure it's 10mm² cable?

It would be less common to have a 10mm² cable on an older BS3036 fuse box (not unheard of though). I wonder how good the last spark was if he did work last year and didn't install an RCD, which would almost definitely be a requirement of the MI and probably required by the 17th edition depending on what level of "intallation" he was actually doing...

 

[dirty harry]

It could be the shower, it could be the cable. Or something else maybe.

What power is the shower rated at? Are you sure it's 10mm² cable?

It would be less common to have a 10mm² cable on an older BS3036 fuse box (not unheard of though). I wonder how good the last spark was if he did work last year and didn't install an RCD, which would almost definitely be a requirement of the MI and probably required by the 17th edition depending on what level of "intallation" he was actually doing...

It's a 9.5kw shower and the cable is definitely 10mm. I have to question why the electrician that fitted it did not replace the older fuse box with a proper MCB/RCD shower consumer unit, which the product instructions clearly said he should have done to comply with the warranty. Anyway, that's all in the past so, starting with the cheapest option, I've suggested to the customer that they have the old fuse box replaced with a proper shower consumer unit and see if that cures the problem. If it doesn't, it'll be a new shower!

 

[bongos]

I've suggested to the customer that they have the old fuse box replaced with a proper shower consumer unit and see if that cures the problem.

While having a shower CU incorporating a RCD is definitely a good idea, I still think it's likely there must be a fault elsewhere, possibly with the cable.

However, any spark installing a shower CU will test the cable as part of the work so at least it will show up if there is a problem.

 

[dirty harry]

I've suggested to the customer that they have the old fuse box replaced with a proper shower consumer unit and see if that cures the problem.

While having a shower CU incorporating a RCD is definitely a good idea, I still think it's likely there must be a fault elsewhere, possibly with the cable.

However, any spark installing a shower CU will test the cable as part of the work so at least it will show up if there is a problem.

True, but would it not be odd for the cable to start playing up after a trouble-free 12 months? Having looked closely it was obviously brand new when it was installed a year ago.

 

[ban-all-sheds]

the cable is definitely 10mm.

Just to be sure.....

//www.diynot.com/wiki/electrics:flatpvccables

 

[dirty harry]

the cable is definitely 10mm.

Just to be sure.....

//www.diynot.com/wiki/electrics:flatpvccables

Thanks for that, a useful bit of info - it's definitely a 10mm and I did see 10 stamped on the cable too.

 

[ban-all-sheds]

OK.