Economy 7

misterstingy · 18 September 2015 at 7:37PM

I'm really confused about the way economy 7 works. I thought that if you have an economy 7 account, all the electricity that you use between the designated hours (usually midnight to 7am) is cheap rate.

It doesn't seem to work like that. We have a flat which seems to have a separate cable coming out of the meter that is the cheap rate cable. AFAICT it's only connected to the Pulsacoil water heater, which heats the water at night. There is a separate connection to the water heater for the boost facility, which runs on the daytime rate.

So it seems that the only thing that operates on economy 7 is the water heater (we don't have storage heaters, just wall-mounted panel heaters). So operating e.g. the washing machine after midnight wouldn't save us anything. Is that right?

What happens to the cheap rate cable during the day. Does it not supply any power, or does it still supply power but charge the full rate for it? I'm thinking if the timer that controls the water heater is set slightly wrong so that it's 'on' time goes past 7am, would it just stop heating the water or carry on heating it at the non-cheap rate?

molerat · 18 September 2015 at 10:11PM

Generally their is extra cables going to a separate consumer unit for the items that operate only on E7 and is only energised during the E7 hours but all of your electricity is at cheap rate during the E7 hours. If you have a timer on the water heater it is probably not connected to the E7 only supply and you need to ensure it is set to operate only during E7 times. It should be quite simple to check - does the timer have a manual override ?

[Deleted User] · 18 September 2015 at 10:22PM

Eco 7 usually operates with the cheap 7 hours active for the whole system.Check if the day rate advances at all when the cheap rate is on. The 7 hours can vary wildly depending on what sort of timer switch you have to control the switch over.Old analogue 24 hr circular timer switch can have the cheap 7 hrs operating anywhere in the 24 hrs. Meters with built in timers are usually correct to within an hour and radio teleswitch timers accurate to a minute or so.

dogshome · 19 September 2015 at 9:37AM

Just how old is this flat?
When ECO7 metering started it had two seperate meters, one for Daytime power and another which was coloured white for cheap Night power, which did indeed only supply power to Storage Radiators and a Hot Water tank.

misterstingy · 19 September 2015 at 3:36PM

The block of flats is only ten years old. Pulsacoil water heaters have two heaters, one connected to the E7 supply for overnight heating, They are designed to keep it hot until you need it. The other heater is connected to the normal elec supply and is only to be used if you run out of hot water. You switch on a boost button to use that heater. Obviously that should be used minimally otherwise you are defeating the object of overnight heating on cheap rate.

I think the timer was installed in the supply route in case you don't need the water heated for the whole 7 hours of the cheap rate period. Pulsacoils don't have a timer themselves, the timer is on the wall beside it.

I think I understand it now. Things like Pulsacoil water heaters and storage heaters are connected to an E7 only supply cable so that there is no chance of them using full rate elec., but everything else can use cheap rate elec. in the cheap rate period. (If I've grasped it right!)

Richie-from-the-Boro · 19 September 2015 at 9:22PM

You have Gledhill water heater, they have different ones for different outputs.......... Yours should be a 3kW Off-Peak immersion heater and a 2.3kW On-Peak boost immersion heater. The Off-Peak should supply the bottom element and the On-Peak the top one and should be wired :

- isolator switch ~to~ off peak controller ~ to top & bottom elements

The off-peak should as you say be automatic @ 35°C with the unrestricted on-peak supply able to be switched manually by the householder using the button on the boost controller. These buttons should act on each other - such that internally - both can never be on at the same time.

This is the schema for a split Consumer Unit i.e. separate on and off Peak supplies, different wiring exists for Combined On And Off Peak Supplies and different again for On Peak Only Supply :

Best of luck.

misterstingy · 27 September 2015 at 5:18PM

that everything else in the flat will be using peak rate electricity e.g. washing machine etc.even if used in the middle of the night (our wiring is as shown in your diagram)?

As our off-peak supply to the pulsacoil has had a timer placed in between the fusebox and the pulsacoil, how long would the pulsacoil normally be set to come on for i.e. would it heat the water sufficiently in say 1 hour, or does it not matter if it's set to be on for say 6 hours because a thermostat switches it off when the water is at the required temperature?

ChumpusRex · 27 September 2015 at 6:23PM

misterstingy wrote: »

I'm really confused about the way economy 7 works. I thought that if you have an economy 7 account, all the electricity that you use between the designated hours (usually midnight to 7am) is cheap rate.

You thought correct.

What happens to the cheap rate cable during the day. Does it not supply any power, or does it still supply power but charge the full rate for it?

The cheap rate cable is de-energised during the day.

Cardew · 27 September 2015 at 6:57PM

misterstingy wrote: »

I think I understand it now. Things like Pulsacoil water heaters and storage heaters are connected to an E7 only supply cable so that there is no chance of them using full rate elec., but everything else can use cheap rate elec. in the cheap rate period. (If I've grasped it right!)

You thought correct.

Not always, depends on the wiring.

1. Most properties now are wired so all the electric supply is at cheap rate(off peak) for 7 hours and at peak rate for 17 hours.

2. However years ago many properties were wired so only Storage heaters and Immersion heaters get off-peak supply for 7 hours and all other electricity(to sockets, lights etc) are on peak rate 24/7.

As dogshome states above in post#4 I also thought that was only on old properties, but we have had posts on MSE stating their newish blocks of flats are wired as explained above in paragraph 2.

It will be easy enough to check, just observe the meter during the 7 hour period and see if the peak rate meter is moving.

misterstingy · 28 September 2015 at 6:12PM

The block of flats was built in 2005, so certainly not old. It seems that there are various possibilities depending how it was set up.

Economy 7

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