Shower isolator switch problem

[willin]

I wonder if anyone can help/advise, I have a Triton T70GSI 10.5Kw (herein could lie the problem – 10.5Kw) shower, It’s wired to a B40 MCB (Crabtree) 40A miniature circuit breaker in the consumer unit. And a 50A ceiling isolator switch.

The house is around 22 Y O so I would think it’s been done somewhere near todays wiring specs, after around 6 – 8 years I had to replace the ceiling switch as it stopped working I did notice it was a little brittle and had been getting hot (by the looks). Same again after around the same amount of time but the wiring insulating was looking discolored (from heat), I ignored it when I probably should have had it checked out, lately the shower refused to switch on so I checked the shower solenoid/feed etc with a multimeter, all fine. took the switch off and found this (see pictures).

Doing a google search on this apparently it’s a fairly common problem, I had a 45a switch so have put that on temporary and I’m switching the supply off by the consumer unit for now.

My thoughts are to strip the wiring back a little and fit a 50a switch, crabtree seems to be the recommended switch, can any electrician/anyone offer any advice? Does any of the wiring/switches need something different?

 

[nara]

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[IANB]

If you dont get these connections proper and tight it will heat up and arc giving the results shown.

 

[miggy]

Cut the neutral wire back and refit. It looks like it's been arcing due to it not being fixed tight enough.

 

[wiz569]

Is the cable sized correctly?
Should be at least 16mm2 for a 10.5kw shower I think.

 

[miggy]

Is the cable sized correctly?
Should be at least 16mm2 for a 10.5kw shower I think.

wiz wouldn't the live wire show signs of burning if it is overloading?. I would change that switch, cut back the neutral wire and refit checking that all connections are tight as @IANB states.

 

[IANB]

wiz wouldn't the live wire show signs of burning if it is overloading?. I would change that switch, cut back the neutral wire and refit checking that all connections are tight as @IANB states.

Incorrect wire gauge will cause heat build up due to higher resistance. The neutral connection looks like it’s been loose and created a point of high resistance. Might be better getting a freindly spark to give it the one over and I would definitely change the switch.

 

[miggy]

Incorrect wire gauge will cause heat build up due to higher resistance. The neutral connection looks like it’s been loose and created a point of high resistance. Might be better getting a freindly spark to give it the one over and I would definitely change the switch.

Ian if it's worked for years and only a switch has been replace then I suspect the switch has been fitted incorrectly. If the op decides to change the shower for a higher wattage it would definitely need rewiring first to compensate. I would change that switch and wire connections should tightened and then double check. There seems to be far to much bare wire exposure there they should not be showing. Observe after that and if problem persists get a sparky to check it out for there own safety and peace of mind.

 

[wiz569]

wiz wouldn't the live wire show signs of burning if it is overloading?. I would change that switch, cut back the neutral wire and refit checking that all connections are tight as @IANB states.

You could be right @miggy but there is a brown/burn mark further back on the grey flex, where's @Mick when you need him

 

[cactikid]

Bet go and head for an electrified shower now.

 

[chookey]

The manual for your shower suggests a minimum 10mm cable, 45A dp switch and to be protected by a 45A mcb.
Triton Showers is a Nuneaton company less than a mile from me

 

[miggy]

You could be right @miggy but there is a brown/burn mark further back on the grey flex, where's @Mick when you need him

That could be where the arcing has been jumping to when it has all been pushed back in the ceiling mate and all wires have been put inside the back box.

 

[chookey]

That could be where the arcing has been jumping to when it has all been pushed back in the ceiling mate and all wires have been put inside the back box.

Exactly. That part of the insulation would likely be near enough resting over the burnt terminal when the switch was screwed on

 

[Mick]

The circuit load is around 45.6A (10500/230) based on 10.5KW.
Your switches are rated at 45A - should be fine but on the edge.
10mm without looking up regs I thought can take around 50A -70A but that really depends on many factors like:
* Installation method - ie in a wall with insulation and how much insulation.
* Cable grouping - are cables grouped in bunches at points of the cable run...
* Cable type (like T&E).
* Cable length - quote important as volt drop occurs which will push up the Amps.

The weakest point is always the connections, so this is why you are getting the heat generated where the connections are.

9 times out of 10 this is a lose connection, but also connections come lose over time. its good practice to check this switch yearly because its now 2 times this has happened. Torque the connection.

My first advice is always get a professional out, as it might be something else...
they will change your switch, cut your cables back to bright copper, make sure the connections are tight test the circuit.

Mick

 

[willin]

Many thanks for all the advice lads, I remember tightening everything well, I suspect the problem is the cabling don't push back easily towards the back box and maybe they're loosening slightly as I push them back, It is 10mm cable. I think I need to get into the roof space and have the cabling move back freely. Apparently the crabtree pull switches are much better for thightening cable to.

 

[nara]

Apparently the crabtree pull switches are much better for thightening cable to.

That's what I took from that video. They do look pretty bulky, but they seem to be a sensible solution to the cable bunching when you screw down.

 

[miggy]

That's what I took from that video. They do look pretty bulky, but they seem to be a sensible solution to the cable bunching when you screw down.

Good man nara, sound advice, don't be stingy with electrical stuff try and get good quality stuff it will last longer.

 

[willin]

That's what I took from that video. They do look pretty bulky, but they seem to be a sensible solution to the cable bunching when you screw down.

I think this is spot on AND @Mick 's advice to check they are tight regularly.

 

[chookey]

Thirty Indians are killed each day by electrocution. We have a lot of regulations here but they are there for a reason.

 

[miggy]

Thirty Indians are killed each day by electrocution. We have a lot of regulations here but they are there for a reason.

View attachment 135241

And not a cowboy in site.