Electric shower, INTERNAL LOOM MELTED, any ideas of cause?

[platdujour]

I have a 9.5kw Triton electric shower (T80i I think)

A wire that goes from the selector switch to the thermal cut out terminals on top of the heater can has melted through.

I found this out because the heat from the wire had distorted the case, letting in water, resulting in me getting shocked whilst showering the other day.

I have checked the tightness of all the connections through the circuit and they're ok.

Can anyone tell me if it is likely to be caused by a fault in the shower unit or a problem with the circuit feeding it?

cheers.

 

[plugwash]

my guess would be it was something wrong with the thermal cutout that was actually providing the heat and the wire was getting hot just because it was connected to it. Could also have been a bad connection between the wire and the thermal cutout.

The problem is almost certainly not related to your fixed wiring.

 

[bernardgreen]

What ever the cause of the over heating this is a clear example of why EVERY electric shower should be protected by an RCD.

The overheating could have been a failure to open in the thermal cutout allowing the unit to over heat.

Or a poor contact in a worn or corroded selector switch

 

[JohnD]

I hope you will be having an RCD installed on the circuit, and checking the earthing and bonding arrangements. This can prevent the sad results of an electrical fault in the bathroom.

What make and age is the consumer unit that supplies it?

 

[platdujour]

thanks for that.

the consumer unit is old fashioned, with ceramic plug in fuses containing fuse wire.

i am planning to replace them all with plug in minitrips in the first place, something like this - http://www.toolstation.com/images/library/stock/webbig/47919.jpg

will i also need additional RCD on the shower curcuit?

cheers.

 

[JohnD]

You do need an RCD as well

It looks like you have a Wylex Standard CU, possibly even one of the old brown ones

It is unlikely to be capable of safely supplying a modern electric shower

Can you put up a pic of the consumer unit (fusebox)?

 

[platdujour]

i'll be able to put up a picture tomorrow.

i think it's one of the old brown ones. (early 70's ex-council flat)

i don't really want to replace the whole cu at the moment.

can i therefore add RCD between that existing supply and the shower.

if so what sort ...

can you buy 45A RCD FCU's ? (i couldn't find on screwfix)

or could i put a shower supply unit like http://tinyurl.com/yrmq7u between the supply and the shower.

thanks for all your help.

D.

 

[JohnD]

you can't get a 45A FCU

btw you mentioned Ceramic fuseholders. This is probably even older than a Wylex Standard and you will not be able to get plug-in MCBs to fit.

a new CU with RCD or RCBO would be suitable. The supply cable to the shower needs to be rated the same as or higher than the MCB

IMO it would be better to have a larger new CU fitted, even if you only use it for the shower circuit at the moment. Then any future changes can be run from the new CU. The extra cost of the larger plastic box and the fresh air it contains is not high.

If you have two or more CUs you need a Master Switch (100A DP Isolator) between the meter and the CUs so that the whole installation can be isolated from a single switch.

This is Notifiable work under Part P.

 

[platdujour]

http://i20.tinypic.com/12693sn.jpg

http://i22.tinypic.com/o6l4q0.jpg

http://i23.tinypic.com/25umf0h.jpg

 

[JohnD]

edited, I can see them now, looks like a Wylex metal skeleton unit mounted flush.

What does it say on/around the main switch?

 

[platdujour]

apart from the on/off all it says is this:

60A 500v
AC Only
45563

 

[Adam_151]

Then its unlikely to have been designed to take any circuit with a design current exceeding 30 Amps

...Don't shoot the messanger!