In message ,
gna03633 wrote:
Firstly thanks for the advice/comments
How sure are you that the "identical" replacement had the same power
rating as the previous one? I strongly suspect your replacement is
more powerful, as a fused one is likely to be at 30A, giving a maximum
of 7.2kW. Of course, it is possible to get bigger fuses, but they
aren't that common. Don't go fitting a bigger fuse unless the cable is
found to be OK for the larger current.
I had the Aquatronic 8500 for a couple of years, it had blown the fuse
once before and was cutting out all the time. I had the manual left from
the previous owner and checked inside the housing for the rating. I
wanted somthing I could replace myself, so bought the Aquatronic 2 from
Wickes - for £60 or so with 2 years warranty. Everything was in the same
place i.e water/cables etc so was a easy swap.
It may not have been ideal (see other replies) but I have to say that
putting 8.5kW on a 30A fuse is very common in my experience. The fact is
that 8.5kW (approx 35.5A @ 240V) isn't going to blow a 30A rewireable
fuse anytime this century - check out fig 3.2A in appendix 3 of BS7671
if you don't believe me. A 30A rewireable will only begin to think about
blowing for a steady-state current of 55A or more (5 second
disconnection is 87A).
Bear in mind too, all those who have been giving cable ratings for 6mm2
cable, that with rewireable fuses you have to derate everything to 0.725
times nominal (433-02-03) thus 6mm2 cable at method 1 which would
normally give 47A is only rated to 34A.
I was concious of the cable and looked along it length I can see (in the
loft) any size mention, nothing written so measuring the size looked OK.
Should I be concerned about this?. I can easily replace the fuse and
hopefully catridge, but it has scortched some of the bit the fuse
plugs into - can this be replaced.
I went to my local electrical place an bought a 40amp Wylex Catridge (in
the manual for the shower it says use a 45A an 6mm. I also got a
'cutting' of 6mm cable so I could compare. Ive taken off the shower cover
and unscrewed the cable and measured it against, what I got given. They
both look the same size, with multiple strands for the core and measure
around 5mm with my ruler.
So I pretty confident the cable is good and the correct size.
I'd be doubtful that a wrong rating of fuse caused the burning
originally described. As others have pointed out, this is far more
likely to be down to a loose connection somewhere. Putting a 40A
rewireable fuse in won't cure this and is likely to be (as I pointed out
above) well outside the rating of the cable, even at the most lenient
installation method. Ignore what I've said if you've actually installed
a cartridge fuse (looks like a big plug fuse and says BS1361 on it)
rather than a rewireable.
Yes, but fuse boxes always seem to do this. After a few blows, they
look like melted Mozzarella on a pizza. Consider replacing your
consumer unit with a modern one, with RCD and MCB protection.
I seem to remember that the fuse did seem quite loose and maybe that
didn't help.
I would echo Christian's advice - at the least consider adding a
separate CU containing an MCB for the shower even if you don't go for a
full new CU. Screwfix do a couple of nice little units with RCD (may not
be strictly necessary, but good backup) and MCB already installed -
69659 for example, though as this comes with a 50A MCB you'll either
need to change to 10mm2 cable or swap the MCB for a lower-rated one.
Oh yes, and while you're at it, do make sure your supplementary bonding
is up to scratch.
Hwyl!
M.
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