Electric shower - switch problem.

[Nick67GT]

No.2 son using his shower this morning and the RCD trips. Gets out and tried to reset at the consumer unit and it’s having none of it. He said there was a slight burning smell as well.

The switch is now inoperable in that pulling the cord has zero effect as if the contacts are welded together.

I’ve undone the switch and this is the result:

The live wire of the ‘supply’ and the neutral wire of the ‘load’ wire are toasted as you can see. The other 2 appear to be OK.

My question is: should it be OK to just replace the switch, on the assumption that the fault lies within it, or is it more likely that the shower itself is at fault?

 

[dobbslc]

Probably loose connections at the switch. it looks like you have some slack so just cut the cables back and reterminate. The trick is the push the switch back up to the box then gently pull it back down a bit and then put another half to 1 turn on the screws as they will have come loose.
I'd also check the shower unit and D/B connections!

 

[Nick67GT]

Just back from replacing switch. All 4 terminals were certainly not tight and the resultant overheating can be seen on the worst of those affected:

Thanks to @dobbsic for the top tip on reinstalling the new switch cables!

Shower end of cable will be checked as soon as I’ve worked out how to get to it.

 

[brightspark]

its been fitted badly in the 1st place. what kw shower and size of cable ??

 

[mtt.tr]

she looks a loosey goose

 

[Nick67GT]

It’s 6mm2 cable, but I can’t tell the rating from the info I have at the moment.....

 

[WorkshopChris]

I hate those things with a passion they just asking for a problem.
Shower isolator switches with 6mm cables were never fantastic then showers went crazy cables went up to 10mm but the tiny hard to terminate switch stayed the same.
Regardless of any regs if ever we have to have an electric shower the cable will be run back to the DB with a contactor, so the pull cord is just switching the contactor coil.

 

[brightspark]

a quality 50 amp pull switch with 10mm cable properly terminated will not burn out. I replace stacks of them that have burnt out due to larger showers been fitted cheap switches and being badly wired cant say ive ever had to go back to one I have wired in the past or replaced. its back to new consumer units been metal to contain fires from loose wires

 

[RWD3M]

Hi Nick,

Did you get to the bottom of this one?

 

[Barking Mat]

What's the switch rated at?
6mm2 cables probably not the problem. Has the switch cooked?

 

[Nick67GT]

@RWD3M @barking mat

The switch was inoperable, as though the contacts were fused together.

ie. it would not ‘switch’.

I replaced it with a 45A MK switch which is hopefully good quality.

Going to check the tightness of the terminals tomorrow, now they’ve had a while to settle down.

 

[Justme]

Looking at the earth cable I might start checking the rest of the house to see if its all like that.

Red & Black cables went out a long time ago.

 

[brightspark]

I went last week to change a burnt out switch it was wired in 10.0mm cable but had burnt out the guy gave me a poxy cheap 45 amp switch to fit with single screw terminals err put that in the bin and il fit a new 50 amp one that has twin securing screws on each connection and il twist the cores to stop them from spreading out and only conducting on half the cores