Retention Heaters - Single Supply, Dual Supply, What do I need to do?!

solomonkain

Hi,

I'm currently in a mess with some high heat retention heaters in my aim to improve the energy rating of my house. It's an old build and so the wiring isn't particularly modern and I'm trying to get my head around what the best way to install these is.

We've had economy 7 installed by eon and now have 2 electricians telling us different things. One of them is saying we need a new consumer unit (I'm assuming for the off peak electricity) and then a new circuit for each heater as they are dual supply.

The other electrician is saying they can do it as a single supply. Which one should I be going for? Ideally I want to make sure that whatever choice I make is as future proof as possible without breaking the bank. How much of a difference does dual vs single supply make?

If you can also explain how dual vs single supply works I'd appreciate that, I thought that on economy 7 everything was cheaper to run at off peak times and didn't even realise there were different supplies.I was always taught to run the washing machine and dishwasher at night to save money, but I'm pretty certain they only have a single supply?

Swipe

You can do either method if the storage heater have built in timers. What is the difference in quoted costs? I'd imagine the new consumer unit and new circuits quote will be considerably more expensive. If you go the single supply route using the timers, you must be 100% certain that you know exactly what times your E7 off peak times begin and end. This can only be reliably done by watching them change over in person. Do not just accept the times EOn Next tells you as they will just be guessing and won't know the exact times down to the nearest minute. Each electricity meter's switching time is randomly offset (delayed) slightly to prevent power surges on the local substation when the off peak rate kicks in. E7 times stay GMT all year round.

Regarding your other appliances, they will also get cheaper electricity if used during the E7 off peak period. At the end of the day, whichever you choose will come down to cost or your future proofing preference. If your wiring is old and looking ropey, maybe the dual job is worth the extra cost? The electrician prepared to do the single rate job will be able to advise. The other one may have a vested interest in only undertaking the larger job.

A quick search returned these economy 7 times for each region. Pay specific attention to the split times if you are in the South-East region of England:

Economy 7 Times: By Region:
North of Scotland – 7 hours between 22.00 and 08.30
South of Scotland – 7 hours between 22.00 and 08.30
North East England – 00.30 to 07.30
Yorkshire – 00.30 to 07.30
North West England – 00.30 to 07.30
Merseyside & North Wales – 7 hours between 00.00 and 08.00
East Midlands – 7 hours between 23.00 and 07.00
West Midlands – 7 hours between 23.30 and 08.00
Eastern England – 7 hours between 23.00 and 07.00
South Wales – 7 hours between 22.00 and 08.30
Southern England – 23.30 to 06.30
London – 7 hours between 23.00 and 07.00
South East England – Either between 22.30 and 05.30 or 00.30 and 07.30
South Western England – 7 hours between 22.00 and 08.30

solomonkain

Thank for for the reply, just to make sure I understand fully;

Single supply is fine, as long as I set up the heater timing correctly? Is it a case of once it is set it shouldn't need changing again?

I'm guessing not all retention heaters are able to go to single supply if they need to have the timers then?

Swipe

You'll need to check the manuals of yours, but I'm pretty sure that most modern HHR storage heaters now have built in timers that can be used to charge them overnight from the single supply rather than just to open the flaps and switch on the fan to provide heat during the non off-peak electricity period. If they are dual supply fed, the built in timer is normally switched off and is controlled by the E7 live circuit times and managed via the builtin thermostat. The only downside will be to check periodically that your timer is set correctly to match the off-peak window. If you get those wrong, it could be a very expensive error but that would be fairly obvious if you keep a close eye on your IHD and bills.

squirrelpie

A quick search returned these economy 7 times for each region. Pay
specific attention to the split times if you are in the South-East
region of England:

A link to wherever you found the table would be good, especially since it seems to be wrong. I live in the east of England and that entry doesn't correspond to my reality.

Swipe

https://forums.moneysavingexpert.com/discussion/comment/82152701#Comment_82152701

https://www.businessjuice.co.uk/energy-guides/economy-7-times/

https://www.electricityprices.org.uk/economy-7/

https://freepricecompare.com/home-energy/guides/what-are-the-economy-7-times/


The times listed are the opening and closing time ranges. Your E7 hours could fall anywhere in between. I live in the West Midlands and my meter's E7 times are 00:36 to 07:36 so the same applies.

QrizB

I live in the east of England and that entry doesn't correspond to my reality.

We've had several previous threads where de-facto E7 times (even on legacy meters, not just smart ones) are different from the idealised schedule from CEGB / regional electricity board days.

It seems that (rather like the PotC Pirate Code) the schedule is "more what you'd call guidelines than actual rules".

Swipe

Exactly, that's why I mentioned that it's extremely important to manually observe your meter switchover times. No online guide or even the supplier's advice regarding E7 time slots should be taken at face value.

Ildhund

It's my understanding that the timings are a matter for negotiation, between generators and distributors and again between distributors and suppliers. The limits set by generators may well be wider than those offered by distributors, and similarly for the next link in the chain. So it's quite possible for two suppliers in the same distribution area to offer different timings. SP's E8½ shows how flexible the timings can be in area 18. I don't think you'll ever see two neighbours with the same supplier enjoying different E7 offpeak times ...

squirrelpie

https://forums.moneysavingexpert.com/discussion/comment/82152732#Comment_82152732

The second link is correct.The first is not. And the third is wrong as well. My times are 00:30-07:30

Swipe

https://forums.moneysavingexpert.com/discussion/comment/82152804#Comment_82152804

I posted it as a general reference. As I stated in my original post that included those times, no one should be relying on online times or even what your supplier tells you and instead, manually observing their own meter's switchover times.