power shower (fault?)

[Adam M]

Hi folks,

Went to go for a shower this morning, and the shower just cut out all of a
sudden.

The shower's got it's own 30A circuit with a cartridge type fuse in the fuse
box, which was - as expected - blown.

But when I went to remove the fuse, it was DAMN hot - I'd say like 60 - 70
degrees C. Should I be worried? Or should I just go ahead and change it?

Assuming that the heating is just a feature of the fuse blowing, is it
likely that the fuse just blew because it's old? I know fuses just pop for
no apparent reason sometimes.

TIA!

Adam

 

[Bob Peterson]

Hi folks,

Went to go for a shower this morning, and the shower just cut out all of a
sudden.

The shower's got it's own 30A circuit with a cartridge type fuse in the fuse
box, which was - as expected - blown.

But when I went to remove the fuse, it was DAMN hot - I'd say like 60 - 70
degrees C. Should I be worried? Or should I just go ahead and change it?

Its hot because thats the mechanism that causes it to blow in the first
place. heat is generated by current flow through the fuse. enough heat,
and the fuse blows.

I'd be inclined to just repalce it and see if it blows again. you are right
about fuses occassionally just blowing, does not happen all that often, but
it can happen. if the replacemnet blows, figure out whats wrong.

 

[Steve Cothran]

I'd be inclined to just repalce it and see if it blows again. you are right
about fuses occassionally just blowing, does not happen all that often, but
it can happen. if the replacemnet blows, figure out whats wrong.

Might want to check the fuseholder/socket and its connections, too. If
they are corroded or loose, the fuse will get hot enough to open. Or
maybe the fuseholder is just too small for the load.

F'rinstance, you can get a 3AG fuse in a 30A size. Try running 30A
through that little dude for a while.

 

[John]

What sort of shower uses electricity? Is it for the drain? 30a (at 240v?)
is a lot of power for a small pump.

 

[John]

Then why would the shower suddenly cut off? Is the shower valve linked to
the heater?

 

[Arthur Simpson]

check the raiting of the shower. usually in KW. Approx max power raiting
should be no more than 6.9KW for a 30A fuse at 230V.

 

[Steve Mowbray]

Hi Adam

I have had a similar problem to yourself and got some good answers off this
ng.

Basically fuses will carry a lot more current than they are rated at (more
than you would expect) the 30A is only good for 7kW in theory (P=VI, where
V=240) however in practice since the shower is an intermittent load rather
than continuous a higher power shower will seem to run okay within the BS
standard for fuse behaviour but outside its rating and tends to get very hot
as a result.

I suspect that this is the case and the continual heating/cooling as
degraded the fuse rating.

After trawling round a good few local plumbers/electricians and shower
specialists - I have found that it is common practice to exploit this and
fit more powerful shower systems on the basis that they are only on for
short periods (saves on rewiring when a system is upgraded).

This is not to be recommended - check your shower rating (usually indicated
on the heater unit or elsewhere under the cover DISCONNECT BEFORE REMOVAL)
and if it is more than 7kW consider upgrading your consumer unit.

Also check your wiring (should be at least 6 mm but could need up to 10mm)
and any switches/connector blocks in the circuit.

I am not an electrician - just passing on some info you might find useful

Steve

 

[Dave M.]

Adam,

Cartridge fuses age with use. It's possible it's element has deteriorated
over time. I've had to replace these fuses periodically.

Dave M.

 

[Ross Mac]

Hi folks,

Went to go for a shower this morning, and the shower just cut out all of a
sudden.

The shower's got it's own 30A circuit with a cartridge type fuse in the fuse
box, which was - as expected - blown.

But when I went to remove the fuse, it was DAMN hot - I'd say like 60 - 70
degrees C. Should I be worried? Or should I just go ahead and change it?

Assuming that the heating is just a feature of the fuse blowing, is it
likely that the fuse just blew because it's old? I know fuses just pop for
no apparent reason sometimes.

TIA!

Adam

I would put an amp clamp on the heater....If the current flow is somewhere
close to rated...change the fuse, it must have degraded.....good
luck....Ross

 

[Bob]

What sort of shower uses electricity? Is it for the drain? 30a (at 240v?)
is a lot of power for a small pump.

John,
In places other than the US and Canada, hot water for the shower is
created AT the shower in a small dedicated electric "instant" water
heater, a larger version of the types sold now for kitchen sinks. If
you are using electricity for hot water it is actaully more efficient
that the traditional US method of having one big water heater tank and
suffering the heat losses through pipes. I suspect we will be going
that way in the future.