timer for economy 7 immersion heater?

[EFLImpudence]

There are various timers for the different configurations such as:

one element, two elements,

one supply which just changes the rate to one element,

two supplies to two elements,



If you just want a timer to reduce the E7 hours then you will need another supply to power the clock.

 

[tomssi]

Thanks for your response.

That is what I am after, to reduce the E7 usage down to the last couple of hours.

I was wondering if there is a timer designed for this scenario that has a rechargeable battery to retain the timer memory.

 

[phatboy]

You need one of these

http://www.tlc-direct.co.uk/Products/SMTRTD7.html

 

[tomssi]

That looks quite tasty, so it will have a permanent supply via the booster supply.

Cheers for that phatboy.

 

[phatboy]

That looks quite tasty, so it will have a permanent supply via the booster supply.

Cheers for that phatboy.

Permanent, as in 7 hours a day!

 

[SimonH2]

... nobody mentioned that during day / peak time there will be no electricity to this spur, so how would the timer keep its time settings?

It doesn't - you don't need a timer in that situation. When the meter clicks over to night rate, it powers up the off-peak loads which includes the immersion heater. When the meter clicks back to day rate, it turns those loads off.
Bear in mind that a lot of E7 (or similar) installations don't actually use a timer or have fixed cheap rate periods. Many use radio switches so the network controllers can use your off-peak loads as a form of demand management - switch off your storage heaters if there's a shortage of generation, turn them back on again when it's sorted. They typically guarantee you 7 hours within some time window - not 7 hours starting and finishing at set times.

As mentioned, it's normal to have separate elements for "night storage" and "day top up" or "boost". These are wired to the off-peak only and all day supplies respectively.

If you have just one immersion heater, and want to keep the option of running it during the day, then it needs two supplies and a changeover switch. Or it needs a supply from the all day board, and a relay to turn it on and off with the off-peak supply (plus a switch to override the relay).

 

[EFLImpudence]

It doesn't - you don't need a timer in that situation.

But the OP wants to limit the hours of off-peak so needs a timer whose clock will require permanent supply.

As mentioned, it's normal to have separate elements for "night storage" and "day top up" or "boost". These are wired to the off-peak only and all day supplies respectively.

In that case suitable timers are available.

If you have just one immersion heater, and want to keep the option of running it during the day, then it needs two supplies and a changeover switch. Or it needs a supply from the all day board, and a relay to turn it on and off with the off-peak supply (plus a switch to override the relay).

Again, suitable timers are available.

 

[phatboy]

Such as my suggestion

 

[EFLImpudence]

Yes, indeed.

 

[tomssi]

That looks quite tasty, so it will have a permanent supply via the booster supply.

Cheers for that phatboy.

Permanent, as in 7 hours a day!

Would the unit not have power 24/7 with the booster supply connected?

 

[EFLImpudence]

It would - (but not the particular model linked but others are available).

so you do have two elements and two supplies, then?

I don't think this has actually been stated.

 

[SimonH2]

It doesn't - you don't need a timer in that situation.

But the OP wants to limit the hours of off-peak so needs a timer whose clock will require permanent supply.

Does he ? I read it as he wants to limit the hours to off-peak so as to use the lower rate lecky. In that case no timer needed - just power it up off the off-peak supply* and let the stat turn it off when the cylinder is "full". The only reason I can think of when you might want to use a timer is if you want to delay switch on so as to leave the cylinder (partially) cold for an hour or two extra to reduce standing losses - but the savings from that are going to be so small as to not be worth the effort (IMO).

* Potentially with an override facility if he wants to be able to top up during the day.

 

[EFLImpudence]

That is what I am after, to reduce the E7 usage down to the last couple of hours.

 

[EFLImpudence]

In that case no timer needed - just power it up off the off-peak supply* and let the stat turn it off when the cylinder is "full". The only reason I can think of when you might want to use a timer is if you want to delay switch on so as to leave the cylinder (partially) cold for an hour or two extra to reduce standing losses - but the savings from that are going to be so small as to not be worth the effort (IMO).

There is that, of course.

Good point.

 

[tomssi]

I'm getting a bit lost myself now.

There are 2 elements, bottom is E7 and top is permanent.

I was basically looking to avoid having the E7 element boiling on and off through the night for the sake of wasted energy and giving the element longer life.

From my understanding the suggested time controller would be fed by both E7 and permanent supply spurs. The E7 would then be on the 24 hr time control and the permanent / booster would have the ability to manually switch on with the choice of staying on for 30/60/120 mins.

Am i barking up the wrong tree here?