Mira Shower Tripping Out - Cabling Melted (With Pics)

[G00NeR79]

Hi everyone.
Just wondering if any sparkies or plumbers/shower fitters can offer me some advice?

Had my Mira Escape shower for a few years and all has been fine, but a couple of nights ago whilst I was in the shower, it tripped out and I noticed a burning smell.
I opened the shower unit up and sure enough the neutral cable has melted badly:



I checked the other end which runs into the pole switch and all is fine there with no sign of damage:



Is there anything in particular that could have caused this?
The cable runs from a 50amp rcd in the circuit board - into the pole switch - then into the shower. There aren't any signs of water seeping into the unit.

The other thing that is confusing me is that when the shower is tripping out, it's not tripping the 50amp rcd that it's connected too. Instead its tripping a different one out which has a 'test' button on it.
This other rcd with the test button is supplying power somehow? If I switch this rcd off, then pull the pole switch there is no power and vice versa, if I turn the 50amp shower rcd off and leave the test one on, there is no power on the pole switch? Both have to be on.

Hope I've explained myself ok, and hopefully get a bit of advice. I'm a chippy so know a little about electrics, but not that much. Got a few sparkies in work that could take a look, but that won't be until next week and with this scorching weather, it's killing us not having the shower

 

[flameport]

The burnt part has been caused by that connection being loose.

To repair, the burnt connector must be replaced, and the wires cut back to remove all of the damaged section, then reconnected.

The RCD (item with a test button on it) is tripping because the melted mess has caused a fault between the neutral and earth.
The 50 amp circuit breaker won't trip, as that only detects faults between L&N or L&E.

Other than that, the ends of that cable look to have been cut with a blunt bread knife, and the bare copper wire should have green/yellow sleeving over it.

 

[murphy4869]

I'm not a pro but it would seem the neutral in the shower choc block was loose, screw not tight, and the constant heating and cooling over time at this weak point has caused the problem.
I would get a new suitable rated choc block cut back the neutral cable to fresh copper and also the earth as it too looks scorched (which needs sleeving at both shower and switch!!!) and reinstall.
I'm sure some pro will be along shortly to confirm

 

[G00NeR79]

Thanks for the quick responses guys.

Yeah a friend of ours (a plumber) originally hooked up the cabling, hence the slightly messy cuttings

I've had to rip out the old cabling as there was no play whatsoever, so when I re-run it I'll put sleevings onto the earth's. I just need to find a suitable choc bloc then? Do these have a particular rating?

Thanks again

 

[JohnnyG]

You'll need 60amp choc block - http://www.tlc-direct.co.uk/Products/TLCON60.html

 

[G00NeR79]

You'll need 60amp choc block - http://www.tlc-direct.co.uk/Products/TLCON60.html[/QUOTE]

Oh right. I think I've got a few of those in the garage.
I thought it would have to be a different type of block, similar to what was already there as it was secured in place with a T15 screw.

Cheers

 

[Spark123]

Make double sure that it is 60A before you use it as if you use something rated too low it can burn up again.
Are all circuits in the bathroom protected by RCD?

 

[JohnnyG]

Oh right. I think I've got a few of those in the garage.
I thought it would have to be a different type of block, similar to what was already there as it was secured in place with a T15 screw.

Cheers

If you can get one of those from the manufacturers that would of course be the best option (it's probably rated higher) but 60a choc block will do the job safely and it's easier to get hold of.

 

[G00NeR79]

Could probably get the exact one from Mira, but then it would probably take a while and its killing us not having the shower. I'll pop down to my local Gas/Electrics store tomorrow and see what they have, or if it comes to it I'll use the connectors.

@ Spark123 - Yes, all the circuits are protected on the RCD

 

[disinfo]

Classic case of a plumber getting bored by the time it came to tightening up the neutral?

 

[jaysean1]

Looks like a quality install, look at how the grey is stripped back!!!

 

[JohnnyG]

Looks like a quality install, look at how the grey is stripped back!!!

I'm sure it's commonplace but that's the first time I've seen the CPC's on harmonized T&E having both no sleeving and being twisted together.
Old habits must die hard.

 

[G00NeR79]

....but that's the first time I've seen the CPC's on harmonized T&E....

Could you explain what you mean, I don't get the terminology

 

[jaysean1]

its been done by plumbers i bet, or a rough sparky

 

[jaysean1]

cpc is the (bare)earth cable which should have some green/yellow sleaving.

by rights you should not twist the cables together, as you can make the conductor weak