shower cable burning

[davesputer]

hi all . just wondering if someone could help with my shower problem.
i have a 9kw shower which is feed by 6mm t+e ,whilst using the shower i could smell burning which it turned out was coming from the ceiling switch when i opened up the switch the insulation on the cables had burnt away.i cut the burnt cable off and replaced the switch everything fine for 3
weeks then old fuse holder in the consumer unit melted.
is the problem with the shower unit , cable ,consumer unit or all of the
i would be grateful for any advice

 

[Cremeegg]

Your 9kW shower draws 39A and a 6mm cable will at best only be rated at 47A. If the cable goes through any insulation or studwork then its rating will come down to as little as 23A.

You need a qualified electrician who can do the necessary remedial works and notify the works under Part P. He/she will know how to do the calculations to correctly rate the cable, switchgear and fuseboard.

I would strongly advise a new consumer unit or at least a shower unit with RCD protection (as recommended by most if not all shower manufacturers)

 

[canduit]

The fuse holder melted Did the fuse blow? What kind of fuse is it? Hopefully not the rewirable paperclip type....

 

[echoes]

The problem is probably caused by someone's inability to use a screwdriver to tighten the connections at the pull-cord switch and the consumer unit.
Also many old fuse holders are not designed for loads greater than 30A.

If you removed the fuse to attend to the ceiling switch, the fuse may not have been re-inserted properly, or may have had mucky contacts causing a poor connection.

In any case, all overheated cable needs to be cut back to bright, unannealed copper at both ends and the consumer unit fixed or replaced. Maybe a good opportunity to ensure the cable is adequate also in terms of length (voltage drop) and installation method - it may not be.

 

[davesputer]

it was an old type rewire able fuse which did not blow this has now been replaced with a mcb

 

[plugwash]

it was an old type rewire able fuse which did not blow this has now been replaced with a mcb

The trouble is that if the fuse holder (and not just the fusewire) melted then there has likely been heat damage to the contacts in the CU as well as to the fuseholder.

So really if the fuseholder melted the CU should be replaced.