Selection switch

[mutley11]

Is there such an electrical switch which allows you to choose which immersion heater to use in a tank?

At the moment my hot water tank has 2 separate heaters, each 3kW rated. There is a cable running out of each of them which I can plug into the wall socket one at a time.

I know this is not best practice wiring so I plan to put in a switch to choose which immersion heater to use and then wire in a timer to choose the on and off time.

I wonder if a selection switch exists to allow me to choose the heater I want on which can take a 3kW load?

 

[plugwash]

What you are after is a dual immersion heater switch e.g. MK K5207WHI or K5298WHI (the former has a neon, the latter does not).

 

[JohnW2]

What you are after is a dual immersion heater switch e.g. MK K5207WHI or K5298WHI (the former has a neon, the latter does not).

The problem I see with that (rather than the changeover switch the OP had asked about) is that a standard timeswitch on the supply side would be overloaded if both immersions were switched on simultaneously (maybe unintentionally). If, to overcome that, the OP had two separate timeswitches, on the load side of the switches, then their clocks would have to be reset every time they were switched on.

If single pole switching was consdiered adequate, there are 20A 2-way plate switches available (e.g. the MK K4781 D2 WHI), but I don't know how easy they are to find. For double-pole changeover switching, I think one would probably be into something much heavier/bulkier than anything in a standard accessory range.

Kind Regards, John

 

[EFLImpudence]

Do you not have a redundant Economy 7 circuit which could be used?

 

[plugwash]

I was talking about the typw of switch that has two switches, an on/off switch and a sink/bath switch.

 

[JohnW2]

I was talking about the typw of switch that has two switches, an on/off switch and a sink/bath switch.

Ah, right. I hadn't realised that - I thought it was just a 'dual' switch (i.e. 2 gang 1-way DP). Looking at the K5207, it seems that the changeover ('sink/bath') switch is SP, so that's much the same (plus a DP 'isolator') as I was suggesting.

Kind Regards, John

 

[mutley11]

What you are after is a dual immersion heater switch e.g. MK K5207WHI or K5298WHI (the former has a neon, the latter does not).

would overload be a possibility with this as JohnW2 suggested?

if i put in a double pole switch to replace the current socket and from there run to a 16A immersion timer then from the timer run to this selection switch that you suggest.

Then the two immersion heaters run into this selection switch, would I have the problem of having to reset the time on the timer clock when I switch between one heater and the other as JohnW2 suggest?

 

[JohnW2]

What you are after is a dual immersion heater switch e.g. MK K5207WHI or K5298WHI (the former has a neon, the latter does not).

would overload be a possibility with this as JohnW2 suggested?

No. As I wrote subsequently, I had misunderstood what this MK switch was. I initially thought it was simply two identical switches on one plate - one for each immersion. However, it is actually a double pole 'on/off' switch (which would switch off/isolate both immersons) followed by a single pole 'changeover' switch, which would allow the power to be sent to one or the other (never both) of the immersions.

if i put in a double pole switch to replace the current socket and from there run to a 16A immersion timer then from the timer run to this selection switch that you suggest.

Yes, you could do that. In fact, the double pole switch you mention would not be essential - you could simply replace the current socket with the timeswitch. The only downside of not having that extra switch (before the timeswitch) is that you would have to isolate the circuit at your Consumer Uniut if/when you ever had to work on (e.g. replace) the timeswitch.

Then the two immersion heaters run into this selection switch, would I have the problem of having to reset the time on the timer clock when I switch between one heater and the other as JohnW2 suggest?

No. With the timeswitch before the other switching, its clock would run contiuously and therefore would not need resetting.

Kind Regards, John

 

[mutley11]

cheers pugwash and JohnW2 for your help guys. much appreciated.

 

[EFLImpudence]

What would you do if there were only ONE immersion element in the tank?

 

[JohnW2]

What would you do if there were only ONE immersion element in the tank?

Stop asking about changeover switches, I guess Seriously, though, I'm not sure I understand what you are getting at.

Kind Regards, John

 

[EFLImpudence]

Why is it necessary to use both?

Usually, two are for use with E7 and boost.
(My question whether redundant E7 circuit is still there was not answered.)

I realise a boost may be useful occasionally but is it worth the bother.

 

[JohnW2]

Why is it necessary to use both? Usually, two are for use with E7 and boost. (My question whether redundant E7 circuit is still there was not answered.) I realise a boost may be useful occasionally but is it worth the bother.

Although that is, indeed, a common use when one has E7 (I have that very setup), I suspect we're not talking about 'boosting' here. The clue may be in the labelling of the MK changeover switch ('Sink' and 'Bath').

If, for example, one has an electric shower and only rarely takes baths, there will not normally be a need to fully heat the whole cylinder full of water, so the upper ('sink') immersion may well be enough for most (sink + basin) routine needs. Then, occasionally, if one wants a bath, one can switch to the lower ('bath') immersion temporarily ... somewhat the opposite of the 'boost' situation you were thinking of.

Kind Regards, John

 

[EFLImpudence]

Well, learned something today.

I have never come across an installation like that.

Surely, if the OP doesn't have a 'bath/sink' switch then it must have been used for something else.
That is not a reason why that can't be done now, of course.

 

[JohnW2]

Well, learned something today. I have never come across an installation like that.

I'm a little surprised, since I've certainly seen it (or variations thereof) quite a bit. One assumes that 'the man at MK' must have seen it a good few times, as well, to have made an accessory labelled for such usage.

Surely, if the OP doesn't have a 'bath/sink' switch then it must have been used for something else.

According to the OP, the current arrangement is that there is one socket, and a lead with a plug connected to each immersion - so that one can plug in whichever one wants. However, the OP recognised that plug/socket is not ideal for this purpose.

Kind Regards, John