Dual immersion. Need to be able to swap off peak and peak supply easily

[19simon]

I have a customer who has a dual immersion water heater. The bottom element is on off peak and the top is boost on normal. The customer has PV and wants to use his PV output to heat the water, but only in the summer.


I need to come up with a method for the customer to easily swap the off peak from the bottom to top immersion heaters and the peak from the top to the bottom.

The system is as follows

Airing cupboard

2 supplies
One RCD protected b16 peaks

One non RCD protected supply bs3036 fed from contactor operated by economy 7 switch


Winter
bottom immersion fed by off peak - normally on
top immersion fed by peak - normally off

summer
bottom immersion fed by peak - controlled by throttling mechanism according to PV output
top immersion fed by off peak - normally off

I was thinking that I could use a 4 pole changeover switch normally used by a generator or do I need to use some contractors. Obviously I'm going to have to keep the neutrals separate otherwise I'm going to get RCD trips.

Any advice would be much appreciated.

 

[babylonsBurning]

Hi Simon.
Could you swap the feed for the bottom element to the non switched consumer unit?
Then fit timers to the elements that the customer set to what they like?
You should still get the advantage of economy 7 rate, if my understanding is correct.

 

[chopper76]

Just time, or use it betwix 12 and 3 during the summer months, I wouldn't bother over engineering a system that's already being fed with it somewhere else anywhoo

 

[guest119]

Why not fit 3 13a sockets in the airing cupd and plug in whatever suits?

 

[chopper76]

You can't use a plug to supply an immersion htr

 

[guest119]

Since when??????????????

 

[stuartcourt]

Since when??????????????

since ever an immersion is 15 amp min

 

[Spark1979]

If its got an economy 7 time switch on just adjust the time it comes on job sorted, the supply to the economy 7 timer will be fed from the on peak board any way and the in built timer switches it on when the whole house switches onto rate 4

 

[Earthstore]

Look on the PV forum, there are several threads on immersion controllers, to make it work the best you need to use as much export as possible, so it is pointless heating the water at night using economy 7 if the customer will then be out all day when the PV could then be heating it for free.

 

[snowhead]

If P.V output was consistant you'd benefit from doing this, but it isn't.
You're likely to be using day rate electricity to power the immersion some of the time that you think P.V is powering it.

You'd need to use an Immersion heater P.V controller which only powers the heater when the P.V output is good enough.
If it's a small P.V system I doubt the costs make it worthwhile doing anything.

 

[19simon]

Thanks for the suggestions.

The customer has some triple rate deal where stored heat is about 1.5p less than night rate.

Am thinking of rigging up a couple of 16 amp commando plugs and sockets so they can be swapped over easily.

its a 4kw system so it's worthwhile using the PV to heat the water. The house is all electric

 

[lauriehurman]

Why not use an intermediate light switch and a relay?

Laurie