2 Gang Immersion heater switch

[David00000]

Hi,

I'm want install a new switch for the immersion heater. Currently there is a two gang socket in the airing cupboard. The immersion plugs into one socket and the water pump into the other (this is in a second floor flat). The plug for the immersion heat burntout/melted at on of the connection pins a few months ago. As a temporary measure I replaced the 2 gang socket with a new RCD socket and heavy duty plug. I now want to change this for a 2 Gang DP cooker switch & 13 A switched socket like this one availale at screwfix.

https://www.screwfix.com/p/british-...-13a-dp-switched-socket-white-with-neon/52668

This is a 45a Cooker swtich will it work for an immersion heater?

Thanks in advance

 

[jj4091]

You may find a cooker switch will not fit into the existing back box and that you need a deeper one, so probably fitting a new single gang switch and back box will be easier. Then use a 13A fused spur for the pump.

 

[EFLImpudence]

On which circuit are the immersion and pump?

A 15A/16A immersion heater circuit or the general 30A/32A socket circuit?

 

[ericmark]

An immersion heater should not be powered from a ring final, and a 13 amp plug is not suitable for the load and time loaded to supply an immersion heater.

The fused connection unit does seem to be more able to supply an immersion heater, but normally they would have a dedicated supply.

 

[Harry Bloomfield]

The fused connection unit does seem to be more able to supply an immersion heater, but normally they would have a dedicated supply.

..and be rated 20amps..

 

[ericmark]

My own immersion is supplied from a FCU, but it rarely is fully loaded, and it only heats top of tank so does not stay on for that long, years ago they would be supplied from a 15 amp plug and socket which has no fuse so does not get hot.

 

[securespark]

In my young days, some immersion heaters were around 15A, on a 15A radial circuit, usually run in 2.5.

But most were 13A. Certainly now, I have not seen any IHs greater than 13A.

In my previous home, built in 1968, it had an immersion heater wired to the first floor ring final. I didn't see it as an issue, because the load on the circuit was small and the heater rarely used.

If the OP's immersion is on a 16A dedicated circuit, I would fit a fused connection unit with a 13A fuse for the immersion and a fused connection unit with a 3A fuse for the water pump.

 

[plugwash]

It's fine to use a switch with a hiher rating than nessacery, and I don't see anything fundamentally wrong with using a cooker control unit for something other than a cooker. However, there are a couple of things you should think about.

1. Overcurrent protection. The fuse in a 13A plug provides overcurrent protection, the cooker control unit won't provide any, if it's already on a 16A or circuit this is a non-issue, but some may be uncomfortable connecting an immersion heater direct to a 32A circuit. Particularly if there is no RCD protection.
2. Cable restraint. Plugs come with a cord grip, as in many (though not all) cases do FCUs and 20A switches. Cooker control units don't, they are expected to be connected via fixed wiring to a seperate cooker outlet plate. So if you use one in this application, you will need to find some other way to restrain the flex for the heater.

 

[ebee]

I would not like to fit a plug or an FCU to a bog standard 3KW immersion heater. I would fit a 20A DP switch (or greater). The OPD at circuit origin should take care of short circuit and earth fault (unless a TT system in which case, normally, an RCD should be used). You don`t require overload protection on the immersion heater, it is a fixed load.

That`s for sole use as an immersion heater circuit.
If you adding a pump then yes it could overload but using a FCU or SFCU with a small fuse inside would be to prevent pump overload and give some protection against the circuit as a whole overloading - OK some might suggest that the whole circuit now requires overload protection but in reality that might be slightly pedantic.

What type and power is the water pump? If it`s just run off a 3A fuse I don't think I`d worry too much.
All depends on your cable size and OPD (Fuse/MCB) rating and whether a ring final circuit or a radial circuit.

 

[SUNRAY]

It's fine to use a switch with a hiher rating than nessacery, and I don't see anything fundamentally wrong with using a cooker control unit for something other than a cooker. However, there are a couple of things you should think about.

1. Overcurrent protection. The fuse in a 13A plug provides overcurrent protection, the cooker control unit won't provide any, if it's already on a 16A or circuit this is a non-issue, but some may be uncomfortable connecting an immersion heater direct to a 32A circuit. Particularly if there is no RCD protection.
2. Cable restraint. Plugs come with a cord grip, as in many (though not all) cases do FCUs and 20A switches. Cooker control units don't, they are expected to be connected via fixed wiring to a seperate cooker outlet plate. So if you use one in this application, you will need to find some other way to restrain the flex for the heater.

47mm box with cable grip, some shallower also available in some ranges

 

[David00000]

On which circuit are the immersion and pump?

A 15A/16A immersion heater circuit or the general 30A/32A socket circuit?

The immersion heater is on a dedicated circuit I am not sure what the A is of the circuit. I am not sure about the water pump but given that it is plugged into the same 2 gang socket as the immesion heater I imagine that it is on the same dedicated circuit as the immersion heater? Attached is an image of the fuse box with the dedicated circuit for the immersion heater ciricled.

 

[David00000]

I would not like to fit a plug or an FCU to a bog standard 3KW immersion heater. I would fit a 20A DP switch (or greater). The OPD at circuit origin should take care of short circuit and earth fault (unless a TT system in which case, normally, an RCD should be used). You don`t require overload protection on the immersion heater, it is a fixed load.

That`s for sole use as an immersion heater circuit.
If you adding a pump then yes it could overload but using a FCU or SFCU with a small fuse inside would be to prevent pump overload and give some protection against the circuit as a whole overloading - OK some might suggest that the whole circuit now requires overload protection but in reality that might be slightly pedantic.

What type and power is the water pump? If it`s just run off a 3A fuse I don't think I`d worry too much.
All depends on your cable size and OPD (Fuse/MCB) rating and whether a ring final circuit or a radial circuit.

It is on a Radial circuit I believe (image attached of the fuse box). The immersion and the pump are both on a B16 (16A) connection via the fuse box. The water pump is on a 3A fuse. (Second attached image) is the RCD 2 gang socket powering both the Immersion heater and the pump which I have installed recenlty as a stop gap.

 

[SUNRAY]

The immersion heater is on a dedicated circuit I am not sure what the A is of the circuit. I am not sure about the water pump but given that it is plugged into the same 2 gang socket as the immesion heater I imagine that it is on the same dedicated circuit as the immersion heater? Attached is an image of the fuse box with the dedicated circuit for the immersion heater ciricled.

On that basis a cooker switch will suit your situation well, at least electrically. Mechanically you wiil need to ensure the heater flex is correctly restrained as already noted.
If the existing backbox is not deep enough and difficult to change there are spacer plates availablehttps://www.screwfix.com/p/schneider-electric-lisse-2-gang-spacer-white/2105j

 

[SUNRAY]

We crossed in the posting

LAP 2-Gang Surface Pattress Back Box 46mm - Screwfix

Order online at Screwfix.com. LAP range combines great engineering with an elegant, slimline design. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

LAP 45A 2-Gang DP Cooker Switch & 13A DP Switched Socket White - Screwfix

Order online at Screwfix.com. LAP range combines great engineering with an elegant, slimline design. Supplied with fixing screw and covers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

3KW = 13A + 3A for the pump fuse = 16A total.

game, set and matched

If you want to stay with metal the one SF do https://www.screwfix.com/p/knightsb...ched-socket-with-led-with-white-inserts/616vf and https://www.screwfix.com/p/vimark-nylon-male-comp-gland-20mm-2-pack/651vt

 

[David00000]

We crossed in the posting

LAP 2-Gang Surface Pattress Back Box 46mm - Screwfix

Order online at Screwfix.com. LAP range combines great engineering with an elegant, slimline design. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

LAP 45A 2-Gang DP Cooker Switch & 13A DP Switched Socket White - Screwfix

Order online at Screwfix.com. LAP range combines great engineering with an elegant, slimline design. Supplied with fixing screw and covers. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

3KW = 13A + 3A for the pump fuse = 16A total.

game, set and matched

Thank you, much appreciated!