new immersion heater control

leafyman · 18 Nov 2018

Hi,
My new hot water cylinder, unvented type, has two electric immersion heaters. I need a controller which will do two things:

1. automatically turn on and then automatically turn off the lower heater at night, during the Economy 7 hours
2, allow me to use only the upper heater as a booster during the daylight hours when I need to.

My only experience of such a controller was many years ago and I found it very complicated to use. I'd be grateful if someone could advise me on a simple device that will do what I want.
Cheers

ericmark · 18 Nov 2018

Economy 7 is a tariff not a system, so it does depend on how your system is wired, there are units like this

but as it if required in your case depends on how it is wired already.

AndyPRK · 18 Nov 2018

these modern tanks seam to come with 2 elements when they get above 170 litres.

Do you have a supply in your house that is only active during E7 period? If yes, just connect to to the bottom element via DP switch.

You can then use a small square booster timer on the top element for normal supply

e.g
https://www.ebay.co.uk/itm/Timeguar...031505&hash=item43e0eadf70:g:9l4AAOSwGJlZLn5e

If you don't have a switched E7 supply, use one of these and set the timer to be within E7 hours

https://www.ebay.co.uk/itm/Timeguar...659718&hash=item416f5ca9f5:g:aawAAOSwvg9Xa6pt

(you don't require the 1st item then as its built in)

If the tank is 200l+ you may wish to consider a way to have the top element on during E7 hours. I'm not sure about this though.

leafyman · 19 Nov 2018

I had to go away for the day yesterday, so I rigged up a simple on/off switch, on the lower heating element, to see if things were working right. Coming back this morning I found the tank nicely hot and the shower working much better than when we had a gravity fed system. Hooray.

I don't see now why I need a timer switch at all. I shall be switching the immersion heater on at 1am in a couple of hours time and turning it off at around 7am. These hours fit in well with our life style. I there is anything against this idea, please let me know.

I want to thank the posters to this thread. It's always nice to to know that there are people prepared to help.

Best, leafyman

terryplumb · 19 Nov 2018

make sure the switch is rated 20 amp. And double pole . did the bottom element not already have an isolation switch ??

leafyman · 20 Nov 2018

Ah, I didn't think about 20amps. Or double pole. I just used the sort of 13amp switch that we have on our storage radiators - quite how they are rated I don't know. Is there a make or model you'd recommend?
There's no isolation switch built on to the heater head as far as I can see.. However, the instructions say that a separate box should contain a 'wiring junction box for primary system'
The plumber is coming tomorrow for the final check over and I'll raise this point with him.

flameport · 20 Nov 2018

leafyman said:
I just used the sort of 13amp switch that we have on our storage radiators

If those have a fuse in them, they are the wrong type - including those for the storage heaters.
Any 20A switch such as these examples is suitable. No fuse required.

If your storage heaters are automatically controlled (as in you don't have to turn them on/off every day), the lower immersion should be wired to the same system, then you can just leave the lower switch on all the time and it will heat up overnight with the storage heaters.

AndyPRK · 20 Nov 2018

Do you have 1 or 2 consumer units/fuse boxes ?

A picture would be good

leafyman · 20 Nov 2018

Things are getting interesting..The plumber sent an apprentice to check things over and he didn't know about the wiring box for the primary system. Hmm

Now I think that the idea of wiring the lower heater to the economy 7 system is a very good one. And a separate booster switch, too, on the daily rate. So I've photographed the econ 7 consumer unit for your info.

Oh dear: . We have seven storage radiators in our bungalow but only 6 mcb's in the consumer unit. We must have one mcb supplying two rads. Maybe that ought to be changed regardless.

If I want to connect the hot water cylinder lower heater to the Econ 7 consumer unit it seems i will need a new 8 way jobbie. (The cylinder heater is supplied now from one mcb in the larger consumer unit).

I hope someone understands the layout in the Econ 7 consumer unit. I dunno what the two mcbs on the left do.

leafyman · 20 Nov 2018

Ouch. I didn't get the photos on. Trying again. No luck. I have the jpg numbers of the snaps I have in my computer. How do I get them into a reply?

leafyman · 20 Nov 2018

Well I dunno how I got two the same. Here goes again

ban-all-sheds · 20 Nov 2018

Now you've got the same one 3 times.

ban-all-sheds · 20 Nov 2018

leafyman said:
I don't see now why I need a timer switch at all. I shall be switching the immersion heater on at 1am in a couple of hours time and turning it off at around 7am. These hours fit in well with our life style. I there is anything against this idea, please let me know.

It relies on you always working properly as a timer switch.

ban-all-sheds · 20 Nov 2018

leafyman said:
I dunno what the two mcbs on the left do.

Have you tried turning them off?

Have you looked inside to see if they are actually connected up?

flameport · 20 Nov 2018

leafyman said:
We have seven storage radiators in our bungalow but only 6 mcb's in the consumer unit.

I can see 8 - which would match very well with 7 heaters and one for the immersion.
Two are LeGrill rather than Proteus, but that doesn't really change anything.

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