My plumber fitted a new (very nice) shower that requires a 40 amp
supply onto the existing wiring which is 30 amp, after 10 minutes
under the shower it will cut out as the fuse trips (and is v.hot). I
like the new shower and don't want a less powerful one. It is on 6 mm
cabling and is directly connected through a wlex box that has 30 amp
written on it. What I want to know is if I buy a replacement fuse for
this box that is rated 40 amp will it work as required. I've seen
and think that it would fit, do you guys think this will be safe? This
would mean the white box would remain (that has 30 amp written on it,
but there would be a new fuse/mcp of 40 amp in it so that would be
Cheers Matt OC
What about the cabling? According to this website
http://www.kevinboone.com/cableselection_web.html table A1 about 2/3
down the page you need 10mm^2 cabling for a 40 amp supply. You really
need to rewire with the larger cable to avoid the possibility of a fire.
Replacing the fuse increases the danger. Ok replacing the fuse by a MCB
changes things slightly as it will blow sooner than a piece of fuse
I may be wrong but I reckon your plumber has bodged the job and put your
life in danger. But I could be wrong and I hope I am. But please get it
checked by a competant electrician before you do anything as rash as
change the fuse.
You will pay for your sins. If you have already paid, please disregard
Actually, you're right.
The fuse is doing its job and saving you from a fire.
However repeatedly abusing the fuse may itself result in a fire.
You should have stopped using it the first or second time it blew.
In some limited circumstances, the cable could be OK. You
need to get it checked by an electrician, who can advise if
the cable needs replacing, or if it's OK just to replace the
fuse. He also needs to check the earth bonding is up to spec,
and the earth fault loop impedance is OK with the fuse being
used. It doesn't sound like the plumber was electrically
competent, and his work needs checking and correcting.
[email address is not usable -- followup in the newsgroup]
6mm is OK for 42A if surface wired. If its not buried in plaster it
should be OK right?
Legaly I think because of Part P the plumber shouldn't have wired it
up because its in a bathroom.
If its a 9.5KW shower then it should be on 10mm cable , if its an
8.5KW shower it should be OK on 6mm, but because of the OPs
inexperience he should get an electrician to confirm.
IIUC, the advice to fit 10 mil is quite recent and many <10kW showers
are around that have been run in 6 mil. After all, the thing is only
going to be on for a few minutes, and possibly only a few minutes a day
and the cable dissipation is only going to be a few watts per foot.
But having an MCB keep tripping (I really can't see the OP constantly
rewiring fuses or fitting replacments, so I guess it is an MBC) - isn't
on. Apart from anything else, it means finishing off the shower with
cold water or leaving a load of shampoo in your hair...
So the OP can either fit a bigger MCB and hope that nothing catches fire
or melts and hope that any fault doesn't leave the thing live, just as
the tresemme hits the tresses..
Or call in a proper electrician, who will no doubt suck teeth, rewire in
10 mil give an inspection certificate and leave the OP with a big bill
and a lot of peace of mind.
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