DIY Doctor UK DIY Forums

Hi, Had electric shower installed, 10mm cable from shower to 45a isolator switch then a direct feed 2.5mm cable to consumer unit a nsb40a circuit breaker on fitted to RCD side of unit. Was working great but then 40a breaker tripped.when put it back on isolator switch on but shower wont turn on.
Any ideas?

2.5mm² cable from isolator to consumer unit is far too small. 2.5mm² even clipped direct to metal tray to remove the heat can only take 27 amps that 6.2Kw and I have never seen a shower that small. In an insulated wall it is only ratted at 13.5 amp thats 3.1Kw it would act more like a fuse wire and I would turn the power off and rewire ASAP.

Sorry but cabling is all 6mm,from shower through isolation to consumer unit.

That's a little better 6mm² is rated at about 35amp or 8Kw and 40amp is 9.2Kw you do not say what size the shower is really should be 8Kw or less. The larger MCB are getting very near to max for the size of breaker and if overloaded do sometimes fail. Sometimes they look as if they have reset but haven't is there a neon on the isolator and if so is it lit. Which what you tell us there is very little we can do to help really does need site visit to sort out this sort of fault. Do you know shower size?

Hi,the shower is 8.5kw,6mm cable running straight thru to isolator with neon,then 6mm cable running direct to 40a breaker in consumer unit,loose cable tripped breaker,reconnected and all seems fine now,cheers