power shower (fault?)

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.

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.

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

heater

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

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.

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

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.

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

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.