"Andrew Gabriel" wrote in message
...
In article ,
"Andy Pandy" writes:
My electric shower blew the cartridge fuse in the consumer unit while I was in it
the
other day, giving me a very refreshing cold shower. I replaced the fuse, and ran
it
for 10 mins or so, and all seemed OK, it didn't blow the new fuse.

Is this something I should be worried about, or do cartridge fuses sometimes blow
with age? The old fuse (and shower) are probably about 12 years old.

It's a 30A fuse, I'm not sure of the power rating of the shower (it's a Heatstore
Esprite II), but I guess it must be taking pretty close to 30A. But it has been
working fine for at least 6 years.

I'm probably being over cautious, but the whole concept of a high power
electrical
device which has blown a fuse in close contact with water which gets sprayed on
me
has started to worry me.

My hunch would be that the original shower was no more than 7kW,
and has been replaced by one which is more, and is exceeding the
fuse (and possibly wiring) rating.

The shower was in the house when we bought it over 6 years ago.

This will blow the fuse, but
only after some time. Check the shower's rating plate.

It's 8.5Kw! How has that been working for 6 years with a 30A fuse?

My second
guess would be the element casing has failed.

Would that not cause it to blow the new fuse pretty quick? I ran it for 10 mins after
replacing the fuse and had a shower this morning and it has been OK.

Would an RCD be advisable?

Depends on the house wiring, type of supply, etc. It can never
do any harm, but it might be completely unnecessary. Showers
do not have to have an RCD unless the earth fault loop impedance
is too high to guarantee the fuse will blow within 5 seconds of
a short circuit to earth.

5 seconds sounds like a very long time - wouldn't 240V for 5 seconds likely kill?

If you don't have the tools to measure
the earth fault loop impedance, you should assume it's too high
to be on the safe side and fit an RCD.

I might get a new consumer unit with RCD. Currently I've got 2 consumer units, one
look fairly new with cartridge fuses, the other looks ancient and has the pull out
rewireable fuses. I've got another shower that runs off the old CU.

What is important is to make sure all the supplementary bonding
in the bathroom is correctly fitted.

I don't think there is any! Would it have been the norm to do this pre 1994 (when I
think this room was converted into a bathroom)? I doubt there is in the other
bathroom either, and that's got a shower over a metal bath!

One question about bonding - I can see it would make the bathroom safe but doesn't it
increase the risk outside the bathroom (by potentially making more things outside the
bathroom, eg radiators, live)?

--
Andy