Any electricians on here?

[Phil-1]

I’m looking for some help/advice.

I had a replacement electrical shower installed before Christmas. This morning I switched it on at the switch and all was fine, went to switch it off and the switch was stuck in the on position. I have removed the switch and the Neutral load side of the switch has melted. I have isolated it at the fuse box.

What could have coursed this?




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[NHN]

The shower switch itself, not the isolator switch?

I would get your installer back, could just be a faulty switch, assuming wiring is ok.

What kw was the previous & the new?

 

[Phil-1]

The shower switch itself, not the isolator switch?

I would get your installer back, could just be a faulty switch, assuming wiring is ok.

What kw was the previous & the new?

It’s the isolator on the wall outside the bathroom. The shower is the same Kw

It’s strange as it’s just the Neutral that’s burnt out.


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[Dadar]

The shower switch itself, not the isolator switch?

I would get your installer back, could just be a faulty switch, assuming wiring is ok.

What kw was the previous & the new?

Or a loose connection in the switch causing high resistance which would cause heat

 

[Phil-1]

Or a loose connection in the switch causing high resistance which would cause heat

That was the first thing I checked. All screws were tight.


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[NHN]

Resistance somewhere if rated same load, but for the cost of a faceplate, swap out & monitor.

 

[RAF_S7]

Was the replacement shower a higher KW than the original?

If so, its possible that the original wiring and switch are undersized for the new showers power rating.

 

[Phil-1]

Resistance somewhere if rated same load, but for the cost of a faceplate, swap out & monitor.

Thanks. I’ve replaced it. And will keep an eye on it. Was surprised it didn’t trip out


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[Phil-1]

At last I’ve spoken to the electrician that installed the new shower and switch. His reply was “ the shower is to high for the cable, you spend to long in it and you should be out after 5mins” and to think I paid him good money to install the correct shower and switch.
I’m not a happy person at the moment as it looks like I now have to pay for another electrician to sort this out


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[NHN]

Whereabouts are you based?

I thought it was the same rating, the guys an idiot.

 

[Phil-1]

Whereabouts are you based?

I thought it was the same rating, the guys an idiot.

North Yorkshire.
Can’t believe he installed a new shower and switch and is now saying this.

Won’t be recommending him to anyone


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[NHN]

What's the mcb value?

 

[Phil-1]

Just remembered he replaced that also.
Think he said it was a 45amp fuse

Need to check it


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[Phil-1]

Just remembered he replaced that also.
Think he said it was a 45amp fuse

Need to check it


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Just had a look and it says “B32” on the trip.
Going to ring another electrician in the morning. Just want to make sure it’s safe


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[NHN]

32amp is ring usually, mines 40, whats the shower rating?

Any pics of the cable & safely measure core diameter of feed & shower cables.

 

[Phil-1]

The shower is a 9.5Kw the cable is 10mm and the switch that burnt out is a double pole isolator switch on the outside of the bathroom. It’s just the neutral part that’s melted.



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[NHN]

What's the rating of the isolator switch thats melted & new.

Should be 40amp mcb imho.

 

[Phil-1]

The switch was a 45amp switch. It was a good make. I’ve replaced it with a switch of the same rating and fingers crossed it’s been ok. And my son has been in the shower for 10mins.


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[SteveMcB]

Your original sparky sounds like a cowboy, tell him to render it safe or you'll lodge an official complaint to NICEIC - regs on all electrical work are really stringent theses days - never mind a 9.5kw shower!!

 

[Phil-1]

Here is a photo of the isolator switch as you can see it’s the neutral connector on the load side that’s burnt. Also the cable is burnt. The copper strands are black and the insulating sheath is brittle

I have someone coming on Saturday to look at it.


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[simonali]

He shouldn't have fitted a higher wattage unit without ensuring every part of the supply was up to the job of feeding it safely. You can't just connect a 42A shower to a cable rated for a 30A one and tell the new owner not to spend too long in there!

 

[Phil-1]

He shouldn't have fitted a higher wattage unit without ensuring every part of the supply was up to the job of feeding it safely. You can't just connect a 42A shower to a cable rated for a 30A one and tell the new owner not to spend too long in there!

I was told that the shower 9.5Kw was the same rating as the old one and that the 10mm cable was the correct size for the shower.

What size cable, Isolator switch and trip should it be for a 9.5Kw unit?


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[simonali]

I think as long as the 10mm T&E isn't installed anywhere where there is thermal insulation it's within the regulated standards. If it's in the loft and under the rockwool then it should ideally be uprated to 16mm. I'm no expert, though, I'm an industrial electrician and don't touch domestic stuff. I don't even tell people I meet I'm an electrician in case they ask about their house!

 

[SteveMcB]

As above, unless it's a really long run or through insulation 10mm cable should be more than enough for 9.5kw, the 45 amp switch should have been just enough as well (load will be around 40-41amps) but it looks quite old, a properly tightened 50amp switch may be the way to go?

I've got a 10 kw on 10mm t/e, 50 amp switch and rcd, cable run about 10m.

 

[Phil-1]

The cable length is approx 5m long and goes up the inside of the wall under the loft insulation and then down to the shower.

I've got an electrician coming at the weekend. If it needs rewriting its not a problem and I can run a new cable and get him to connect/test it


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[Phil-1]

Update.

It appears that the original electrician didn’t tighten the neutral up correctly and that’s what burnt the switch out.




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[MRJ]

Update.

It appears that the original electrician didn’t tighten the neutral up correctly and that’s what burnt the switch out.




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I’d agree with that. I’m a head of M&E for a large organisation, and a sparky by trade and we fit around 200 9.5kw showers per year, designed on a 10mm T&E supply - with longer runs than 5m. I can’t say that any of my managers or electricians would make the comment around 5 minutes as that is just ridiculous. It’ll run all day if you want it to - but you won’t like the cost. The circuit breaker rating won’t affect the switch either. At least you determined it before it got worse.