Emmersion heater

[someonelse]

My emmersian heater is plugged into a normal socket in the airing cupboard.

I read recently that they should be on a separate circuit.

I've lived here for 15 years without any problems so is there any reason either to worry or do anything?

 

[sparkwright]

Are you sure the socket you plug it into is not on a separate circuit?

 

[someonelse]

Good question! Just took a look at the fuse box and there's one trip switch marked "water heater".

Can't think what else that could be so........

Thanks.

 

[sparkwright]

You need to confirm that it is on a separate circuit.

The MCB is normally a 15 or 16 amp MCB, and the circuit wired in 2.5 mm cable. If all this is satisfied a 20 amp double pole switch can be fitted instead of the plug AND socket. (!)

A 20 amp double pole switch with neon indicator is also available.

 

[xr4x4]

You need to confirm that it is on a separate circuit.

The MCB is normally a 15 or 16 amp MCB, and the circuit wired in 2.5 mm cable. If all this is satisfied a 20 amp double pole switch can be fitted instead of the plug AND socket. (!)

A 20 amp double pole switch with neon indicator is also available.

I've seen these wired in with a FCU, is this not the way to do things?

 

[RF Lighting]

Not if its on its own dedicated circuit

 

[xr4x4]

Not if its on its own dedicated circuit

Pretty much all I've seen have been on own dedicated circuit, still with FCUs, hence the question.

 

[sparkwright]

I would say I have very rarely seen a switched FCU for an immersion that's on it's own circuit.

Obviously in the unusual cases when the immersion happens to be fed from a ring circuit a switched FCU has been used.

 

[xr4x4]

Ok, thanks for the info.

 

[kai]

It might be a wise idea to put the 20amp DP switch with indicator on the wall of the hallway or kitchen, or other readily visible location (Circuit wiring permitting) - it makes it far easier to see whether the immersion is actually switched on, without peering inside the airing cupboard.

 

[AdrianUK]

The reason why it isnt advisable to use a plug/socket or FCU with an immersion heater is that a 3kW immersion will pull 3000/230 = 13.04A for an extended period of time. Most 13A accessories simply aren't designed to carry this current for long periods (I know...... its rated at 13A so why can't it carry 13A indefinately.... but the standard only demands 10A indefinately!)

Using a plug/socket or FCU often leads to cooked accessories due to the 13A running hot.

Adrian

 

[JohnW2]

The reason why it isnt advisable to use a plug/socket or FCU with an immersion heater is that a 3kW immersion will pull 3000/230 = 13.04A for an extended period of time. Most 13A accessories simply aren't designed to carry this current for long periods (I know...... its rated at 13A so why can't it carry 13A indefinately.... but the standard only demands 10A indefinately!)

Indeed. That's precisely why, as I've said before, I tend to feel uncomfortable when I see a string of perfectly compliant sockets on a fused spur from an RFC.

Why the standards didn't demand 13A accessories that can carry 13A indefinitely, or double sockets which can carry 2x13A indefinitely will probably always be a matter of bewilderment to me!

Kind Regards, John.

 

[holmslaw]

..

 

[TicklyT]

The elevated temperature inside an airing cupboard probably does little for the current carrying capacity or longevity of a socket either.

 

[ericmark]

My fathers house from new (1951) had a 15A round pin socket for the immersion heater. This was a standard method then so a plumber could change the immersion heater. Back then there were demarcation lines and plumbers would not touch the electrics.

In theory the 13A socket can do the same job but a few years ago the 13A plug was modified so people could not touch the metal of the live pins when with drawing the plug. This has resulted in the pins being less able to distribute any heat generated in the fuse or any poor connections. So although designed during the war ready for the re-build post war to power electric heaters now they are not really good enough for prolonged use at 13A (3kW).

However the idea of being able to unplug is still good and with good quality plug and socket it is unlikely to be a problem. I would still use the old 15A socket if I had an immersion heater as really you don't want anyone to be temped to unplug the immersion to plug in anything else.

But in resent years penny pinching has resulted in the fused connection unit in the main replacing the 15A round pin plugs for this job. And today people are not so afraid of electric as back in 1951 so are willing to delve into the FCU to as required disconnect the heater.