Time of Economy 7

valiant24

By dint of moseying out into the pouring rain and looking at my external meter every few minutes, I determined that my Night rate kicked in this morning at 0148 (so 0048 GMT).

Can I be sure that it will be the same time every night?  It's important as I have a power-guzzling Aga.

Thanks

V

QrizB

Can you be sure? No.

Is it fairly likely? Yes.

What sort of meter do you have? Is it:

• An old analogue one,
• A newer electronic one, or
• A smart meter?

valiant24

Hi, thanks for the reply.

It's a Landis+Gyr E150, fitted by British Gas in November.  It's digital.  Its time is 10 mins behind the actual time.  I saw on YouTube a vid of a similar showing how a flashing number indicates which Rate is active.

Interestingly British Gas website says that Economy 7 rate is 0000 to 0700 if your meter was fitted by them.  Obviously that is not true!

lohr500

If your electric Aga is the same as ours (old original 30 Amp model) and it is wired like ours, then it should have two electrical feeds to it.

A main 32 Amp feed which is permanently live.
A second 5 amp fused feed which is the Economy 7 signal. This feed should be wired back to a separate fuse box/consumer unit which is only "live" during the Economy 7 period.

Are there some isolation switches close to your Aga and do you have one or two?
Do you have a dedicated Economy 7 fuse box?

If you can post a photo of your main meter and fuse boxes, it should be possible to determine how your Economy 7 meter is wired and if there is a separate Economy 7 fuse box. There are several ways this can be configured, depending on the meter type and Economy 7 switch arrangements.

If your Aga is wired as above, then you don't need to worry too much about the Economy 7 time as the Aga will only heat up when it senses the signal on the 5 amp Economy 7 trigger circuit.
The only time it will use the peak rate is if the core temperature drops below a critical level after a lot of cooking during the day.
Ours has a non standard controller fitted as the original was no longer available, but it has an LED to show when it is charging on peak rate. I seem to recall the original controller did the same thing but I could be mistaken as it was replaced many, many years ago!


If your trigger signal is controlled by a separate timer under your control (because there is no dedicated Economy 7 circuit or feed), then it is important to know what the off peak time is and to ensure that the timer is aligned to that time window. And to watch what happens when the clocks change between GMT/BST. In our region the off peak time is fixed on GMT, so any timers also need to be set to stay on GMT and not change automatically with BST/GMT.
Also, if yo do find you have a separate timer, set the timer on/off time to 15 minutes inside the Economy 7 window to allow for any slight drift in either the timer or Economy 7 switching times. And keep a periodic check on both the timer clock and the Economy 7 time window to make sure that a) the timer clock hasn't drifted significantly and b) that the Economy 7 time hasn't changed.


As per QrizB's comments, the consistency of the Economy 7 period will largely be dependant on the type of Meter you have and the method that is used to control any dedicated Economy 7 circuits. As per above, a photo showing your meter and associated fuse boxes/wiring will help to determine how your wiring has been configured.   

valiant24

lohr500 said:

If your Aga is wired as above, then you don't need to worry too much about the Economy 7 time as the Aga will only heat up when it senses the signal on the 5 amp Economy 7 trigger circuit.

The only time it will use the peak rate is if the core temperature drops below a critical level after a lot of cooking during the day.

As per QrizB's comments, the consistency of the Economy 7 period will largely be dependant on the type of Meter you have and the method that is used to control any dedicated Economy 7 circuits. As per above, a photo showing your meter and associated fuse boxes/wiring will help to determine how your wiring has been configured.   

Photos are at https://postimg.cc/gallery/344HZ3g .

I've read for years about this signal that is said to be sent.  I am sure we don't get it (in rural SW England).

Ref the core dropping below a critical level: this is a nightmare too!  (For historical family reasons this is known as "Doing the Naughty Thing"). This is ruinously expensive as my day rate is about 45p/kWh and the night rate only 15p/kWh. So I need to avoid the Aga Doing the Naughty Thing at all costs. But the only way I can think of achieving this is to turn the whole thing off and wait up until 0148 BST to turn it back on again! 

Thanks for the help so far - much appreciated - I am learning lots!!

V

macman

The time will only be consistent if it's a teleswitched meter-you haven't told us. Otherwise it will drift according to the accuracy or otherwise of the clockwork mechanism, and it'll move forward an hour when the clocks go back, as the mechanical meter cannot adjust for this, whereas RTS meters can.

QrizB

valiant24 said:

Photos are at https://postimg.cc/gallery/344HZ3g .

Thanks for the photos, they're interesting but also puzzling.

The meter is a Landis+Gyr 5246C. This is a five-terminal meter with it's own internal E7 clock. It has an internal contactor for E7 plus a 2A auxiliary relay. Either the 5th terminal or the 2A could be used for E7 switching but as far as I can see from the photo there's nothing connected to either option.

Using the 5th terminal or the 2A relay instead of the Honeywell timer would be more reliable (you wouldn't neeed to know the switching times, it would happen automatically) but would require some work by an electrician.

On the plus side, the clocks in those meters tend to be fairly reliable and if they do drift at all it's a slow process.

For historical family reasons this is known as "Doing the Naughty Thing"

Sounds like an entertaining story but probably not one for this forum

EssexHebridean

macman said:

The time will only be consistent if it's a teleswitched meter-you haven't told us. Otherwise it will drift according to the accuracy or otherwise of the clockwork mechanism, and it'll move forward an hour when the clocks go back, as the mechanical meter cannot adjust for this, whereas RTS meters can.

I can’t imagine that BritishGas would be fitting teleswitched meters right now, knowing the signal is due to be turned off? (I mean I know BG’s current record with E7 isn’t the best, but still!) 

QrizB

macman said:

The time will only be consistent if it's a teleswitched meter-you haven't told us.

From the photos the E7 tariff switching is internal to the meter. No teleswitch, no external contactor, nothing.

The Aga is switched by a customer-owned device which needs to be separately synchronised with the meter.

valiant24

QrizB said:

macman said:

The time will only be consistent if it's a teleswitched meter-you haven't told us.

From the photos the E7 tariff switching is internal to the meter. No teleswitch, no external contactor, nothing.

The Aga is switched by a customer-owned device which needs to be separately synchronised with the meter.

Yes this is exactly right.  Synchronised with a meter which is itself showing the wrong time! ;-)

valiant24

macman said:

The time will only be consistent if it's a teleswitched meter-you haven't told us. Otherwise it will drift according to the accuracy or otherwise of the clockwork mechanism, and it'll move forward an hour when the clocks go back, as the mechanical meter cannot adjust for this, whereas RTS meters can.

macman said:

The time will only be consistent if it's a teleswitched meter-you haven't told us. Otherwise it will drift according to the accuracy or otherwise of the clockwork mechanism, and it'll move forward an hour when the clocks go back, as the mechanical meter cannot adjust for this, whereas RTS meters can.

It's not clockwork (only since 2021 though!), it's digital but I take your point.   It currently shows the time as 1410 (it's 1516 BST) so I suspect that it won't adjust for GMT unless it's already 66 minutes slow.