From experience I can tell you that the idea that a 8.5 kW shower will never blow a 30 amp fuse is a complete and utter load of tosh.
I had to install a new consumer unit because the customer had a 8.5 kW shower supplied from a 30 amp Wylex fused switch with a BS1361 cartridge fuse. The fuse blew a few times and was replaced, then the entire switch fuse unit went up in flames, luckily it was on a bare brick wall in his garage so other than soot marks on the wall there wasn’t any other damage.
You cannot have a circuit or protective device which is permanently overloaded by design.
Any way, my question is answered, electricians consider that protecting a 8.5 kW with a 32 amp protective device is acceptable based on custom and practice rather than because they have considered the design requirements.
From experience I can tell you that the idea that a 8.5 kW shower will never blow a 30 amp fuse is a complete and utter load of tosh.
I had to install a new consumer unit because the customer had a 8.5 kW shower supplied from a 30 amp Wylex fused switch with a BS1361 cartridge fuse. The fuse blew a few times and was replaced, then the entire switch fuse unit went up in flames, luckily it was on a bare brick wall in his garage so other than soot marks on the wall there wasn’t any other damage.
You cannot have a circuit or protective device which is permanently overloaded by design.
Any way, my question is answered, electricians consider that protecting a 8.5 kW with a 32 amp protective device is acceptable based on custom and practice rather than because they have considered the design requirements.
