Immersion not coming on overnight on economy 7

25 Aug 2014
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United Kingdom
Hi all,

Bit of advice required please would be much appreciated.

Our immersion boiler no longer comes on overnight to make use of the cheap economy 7 meter. It has 2 heating elements. We leave the top one off except if really required. The bottom one works with our boost switch (E30 simple controller does 30mins, 1hr, 2hr boost) but doesn't come on overnight when left on.

So my question really is where is the timer to let the element know to come on during economy 7 tariff as the element seems to be working fine otherwise?

Many thanks in advance
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Please post a photo of your electricity meter, consumer unit, and the wires and any other things around and between them.
Usually the top element would be on the E30 boost, on an all-day supply and the bottom would be on the E7 on an off-peak supply. This would be with two separate circuits from the consumer units, one all-day and one off-peak.

The E30 controller can't changeover from an all-day to an off-peak supply.
Thank you both for your replies. I will post some pictures when I get in. If the e30 can't be on the economy rate I've got a theory which I can test. In the boiler room itself the switches for the heating elements are placed one above the other and I noticed they are wired weirdly. That is the top switch controls the bottom, economy 7 element and the bottom switch is wired to the top element. I wonder if the e30 is on the bottom element incorrectly and the top element is trying to come on in the night with the economy 7 rate.

Will get back with results, thanks again.
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So I've swapped over the 2 switches and now the e30 boosts the upper element. Here's hoping the lower element now comes on overnight on the economy 7 tariff...

Here's hoping it will be that simple. Thanks again for heads up on e30 couldn't get my head round it. Just out of interest how does it know the timings to come on overnight ie where's the timer?

Thanks again, will post outcome tmrw[/img]

Hope the photos are of some use. As I say the switches in the boiler room were wired oppositely tho this shouldn't have mattered as long as the sparky fitting it knew that and wired in the e30 to the boost element and the main element to the e7. Fingers crossed.

the horstmann box beside the meter contains the timeswitch. Stand back and take a photo showing the runs the cables take between the meter, timer and consumer unit please.
Ah so the timer is actually next to the meter itself? Thanks for that. Unfortunately the meter is outside and the boiler is miles away upstairs in the house so I can't get a photo of it all together. Reckon I may set the alarm and check that the lower heater element comes on in the middle of the night. Or at least check temps tonight and tmrw am to see if it has topped up overnight. Thanks again.
the horstmann box beside the meter contains the timeswitch. Stand back and take a photo showing the runs the cables take between the meter, timer and consumer unit please.

I meant the Horstmann timer, not the one by the hot water cylinder (it is not a boiler). The number of thick cables, and how they are connected, may be of interest. There are two ways off-peak circuits can be connected.

Its clock is radio-controlled, so they very rarely go out of adjustment, but it can happen in a cellar or other location where there is a poor signal.

It will also be interesting to see a photo of the consumer unit(s) with the flap open.

Ok here goes. Hope this is of use.switching the wires seemed to work the large bottom element came on last night on auto and the small one works off the boost switch. Many thanks again
to the extent that I can read it, the CU in your pic only seems to have Heater circuits on it. Have you got storage heaters which correspond to the labels in the CU?

Is there another CU for the sockets and the lighting?
Yes we have night storage heaters as per the tabs on consumer unit. Another one contains all the lights and sockets etc.
then it appears that only your heating and HW gets the benefit of the night-time rate. It looks like your other sockets pay full price at all times, and the supply to the Heating CU is turned on by the timeswitch.

You might want to look into changing tariff, for example if you have a tumble drier or other electrical appliances that could take advantage of overnight prices.

I wonder how the circuits to the immersion heaters got crossed over.
That looks like a dual-tariff board.

"bedroom", "bathroom" and "24 hour water heater" look like 24-hour circuits. on the other half, "storage heater" and "storage water heater" look like off-peak.

The 24-hour half of this board is probably supplied from the left-hand (main) meter through the henley blocks.

It also looks like a Scottish "total heat total control" tariff. SSE / Hydro have a monopoly on this tariff as it uses 2 meters, 3 rates, and other suppliers can't bill it properly.

If this is the case then the dual tariff heating board has been wired up wrongly through the henley blocks. It should probably have been wired completely to the Meter-Teleswitch so all your heating is charged at the lower heating rates. There is probably a 'boost' button on that Teleswitch which will give a boost to the off-peak heaters (storage heaters, and bottom hot water cylinder heater) during the day, at the off-peak rates.

Meter 1 - a standard single rate meter meter (MPAN#1, first 3 digits on MPAN normally 171) This meter measures the Domestic supply (lights, sockets, cooker etc) This is a 24 hour point in putting washers etc on at night as it does not have a cheap rate.

Meter 2 - is a radio Telemeter (MPAN#2, first 3 digits on MPAN normally 172) This meter measures the heating supply and can have 2 or 3 seperate outputs as follows-
- a 24 hour supply for any panel/convector heaters in the house.
- An 80A switched supply, for the storage heaters and hot water (overnight charging).
- A 35A supply for 'boosting' the hot water through the day...if connected this is done by the meter, but can be done manually...if not connected then the boost is supplied through the 24 hour supply.

Moneysavingexpert forum

Possibly your system was installed by an electrician unfamiliar with the system - especially if he can't tell the difference between a peak and an off-peak immersion heater.

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