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Discuss 8.5kw shower on a 32amp mcb in the Electrical Forum area at ElectriciansForums.net

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Hello All
Can any one provide non sarcastic suggestions as to why an 8.5kw shower has not tripped the 32amp mcb protecting that circuit?

Found this install in a domestic property. It seems to have been there for years, without out issue.

Thanks
DD
 
Im just dealing with something similar.
8.5kW on a 30A breaker. This one is actually tripping it, but only if the temperature is high and they spend too long in there.

As in the first post, have a look at appendix 3, page 370 of the new edition of BS7671 and you will see that it is highly unlikely a 32A breaker will trip with a 8.5kW shower (approx 37A-no calculator to hand).
 
Mines 8.5 KW shower is on a 30amp Cartridge fuse and been running spot on for 3 years since i moved in do have a spare Fuse sat in cupboard
 
If it's a B type it would need to get to about 46amps before it started to think about tripping.
8.5 kW @230v is about 37A.
See page 370. BBB

Remember a B type breaker only needs to disconnect within .4 seconds at 5 times it's rated current
 
A few years ago I upgraded a shower cable for a customer, it was an 8.5kW shower on a B32 breaker. It wasn’t tripping & had been in for over 4 years, however there was some discolouring on the mini trunking above the shower. The 2.5mm cable was working beyond its limits!
 
Like has been expressed, the trip curve characteristics explains why the 32amp doesn't trip but relative to design of the circuit we have a regulation that states small overloads for long periods should not be possible so anyone designing/altering this circuit should never have done that in the first place.
 

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