Shower on a a 30a rewireable fuse

[glendower]

Went to do a plumbing job on an Triton Barbados 8kw electric shower, needs a new pressure release device, and I noticed that the insulation on the phase wire was melted slightly. I checked that the terminal was tight and I also checked the Merera 3 CU and found that the shower was wired to a 30a re-wireable fuse.

The shower is wired with 6mm T&E which is adequate for a 8kw but is the the fuse ok I have read that with rewireable fuses the fuse should be of a lower capacity that the load carrying capacity of the cable so that the fuse burns out before the cable is this correct?

Also what would cause the insulation on the phase wire to melt?(Its only about first 20mm as it comes out of the terminal)

 

[Taylortwocities]

Melted insulation is usually a sign that the termination is not making good contact. Either loose or the cable needs to be cut back to bright copper, and clean the screw up so there's good contact.

30A fuse is, as you say, OK for a 6mm cable assuming its not run thru high temperature environment of in insulation, etc. There's no reason to put a smaller fuse in. For those boards there is a max current per way of 30A and a maximum for the whole board, usually 60A - it will say this near the main switch.

Great to see our plumbing friends paying attention to 'the dark side' !

 

[Spark123]

I'd have thought the maximum size shower for a 30A fuse is 7.2kw?
glendower, I think you are getting at the calculated maximum current carrying capacity of 6mm cable is multiplied by a correction factor of 0.725 owing to the use of a rewirable fuse, not forgetting the other correction factors.

 

[Click-Sure]

Great to see our plumbing friends paying attention to 'the dark side' !

Why is it that plumbers always look at sparks with a certain degree cautiousness?
A good mate of mine (plumber) can't understand how no two sparks ever do one job the same way, and I agree with him from my own experience and this forum, which is no exeption.

Could just be all our black magic...

 

[ricicle]

Went to do a plumbing job on an Triton Barbados 8kw electric shower, needs a new pressure release device, and I noticed that the insulation on the phase wire was melted slightly. I checked that the terminal was tight and I also checked the Merera 3 CU and found that the shower was wired to a 30a re-wireable fuse.

The shower is wired with 6mm T&E which is adequate for a 8kw but is the the fuse ok I have read that with rewireable fuses the fuse should be of a lower capacity that the load carrying capacity of the cable so that the fuse burns out before the cable is this correct?

Also what would cause the insulation on the phase wire to melt?(Its only about first 20mm as it comes out of the terminal)

Was it protected by a 30mA RCD?

 

[glendower]

No RCD It is Merera 3 CU with 4 rewireable fuses, 2 x30A, 1x15A, 1x5A. It is the original CU. in a very small one bed bungalow.