Blown shower switch

[andyww]

Hi Chaps

Quick question: - my customer has a shower switch (45a DP neon ceiling pull switch) that went bang a couple of days ago and she's asked me to rectify the fault.On investigation I found: shower is 9.5kw, so draws c. 41amps, on a 40a mcb, run in 6mm t&e. The switch is burned, as are the cables in the switch - there was a LOT of cable jammed into the switch patress, and a couple of the terminal screws were loose. My instinct is to rewire the circuit in 10mm (to cover the potential 41 amp current draw) but she is not overly happy with me lifting carpets, floorboards etc. - I have cut the existing cable in the switch back to the unburnt part and carried out ins resistance tests on both legs (CU to switch, and switch to shower) - all tested fine. Question is, am I right to insist that it's rewired in 10mm - or as an existing installation, can I just change the switch? I believe the switch burnt out due to the loose terminal screws and the amount of cable tightly packed together in the patress - cables are fine in both the the shower and the CU.
Any suggestions/guidance??

Cheers
Andy

 

[Spudnik]

You could always drop in a 32A MCB in place of the 40A.

But, you cant make them have the work done.

It sounds to me like a high resistance joint, either at the terminals or squashed cables.

 

[andyww]

Thanks Jason - appreciate the response. So if I replaced the 40a mcb with a 32, it would then be ok to leave the 6mm - I like the sound of that. Only time it could be a problem (tripping) is when the shower gets older and they need to turn it up more and therefore draw more current?

 

[Spudnik]

Thanks Jason - appreciate the response. So if I replaced the 40a mcb with a 32, it would then be ok to leave the 6mm - I like the sound of that. Only time it could be a problem (tripping) is when the shower gets older and they need to turn it up more and therefore draw more current?

Maybe, but there really should not be a 40 on the end of the 6mm.

If the circuit was designed properly in the first place then this wouldnt have been a problem.

And as the client is not prepared to have he house upside down (which is fair enough)all you can do is explain in detail each option etc.

 

[wrighty141]

The firm i work for used to upgrade bathrooms. we were told that a shower over 8.5 kW with a cable run of over 15m would require rewiring in 10mm if the existing cable was 6mm. so make sure you check the length of run mate. hope that helps a little

 

[andyww]

Thanks guys