Smart meter - what triggers switch to night rate on E7?

I’ve recently switched from EDF to Bulb, on an Economy 7 tariff, after having a Landis E470 (SMETS2) meter fitted by EDF. Since the switch I’ve noticed that whilst my IHD shows that the night rate price kicks in at the correct time (12:30am), the E7 circuit switches on at 11:30pm (this was the time the EDF E7 night rate started).

I had assumed that it was the smart meter itself that controlled when the switch occurred and that Bulb would simply update the meter remotely to switch on the E7 circuit at the new time.

Does anyone know what actually triggers the E7 circuit switch on a smart meter? Can it typically be controlled remotely or would some other adjustment be needed?

How is your E7 circuit connected up? Do you have a 5 terminal meter? As in, an electricity meter with 5 wires connected to it. I was under the impression that no one made those yet. Is your E7 circuit perhaps connected to a different time switch that is separate from the meter? A photo of the installation might help, but be sure to redact any serial numbers or other identifying information printed on the meter.

Thanks for the reply. I do have a 5-wire connection, but the meter is only 4 wires. There’s a secondary unit installed that hooks up the 5th wire and allows the meter to switch between day and night rate. I had wondered whether the secondary unit might contain the timer.

Hmm. So you have a separate contactor for the switched circuit, but looking here it does appear to be literally just a switch and not a timer.

The circuit diagram on the case doesn’t make much sense to me, it’s not clear what signal is turning the contactor on or off. It looks like it must be controlled by that smaller grey connection from the meter, but that doesn’t explain the time difference.

I’m afraid my knowledge here has been exhausted. Perhaps someone else will be able to help. You might need to consult an electrician for advice. The units are all sealed so they wont actually be able to do anything, but hopefully they’ll be able to explain exactly what’s supposed to happen. I would say ask Bulb, but this is a technical question and you’ll likely struggle to get past first line customer support.

No problem, thanks for having a look. I’ll contact Bulb on Monday just in case. I’m hoping the timer for the switch will turn out to be adjustable remotely, but it would certainly be nice to know how it actually works.

Quick update. Still talking to Bulb, but I did manage to get some info from EDF. They claimed that night circuit switch over time is based on post code and can’t be changed, and that my post code switch over time is around 11:30pm. They also claimed this would be the case no matter which supplier installed the meter.

Obviously hard to know if that’s really the case given they’ve got an interest in luring me back because their switch over time syncs up. But if they are correct then it means the Bulb E7 tariff would never fully work for someone in a postcode that switches over before 12:30am.

If anyone is able to confirm whether EDF’s explanation of how it works is right (or wrong), would love to know.

That’s true only for traditional meters with a fixed clock and timer.

Smart meters can change tariff at any half-hourly interval, and is controlled completely by the supplier. That still doesn’t explain exactly what is controlling your external contactor.

That’s what I’d have thought too. I did press them specifically on how it works for smart meters and they claimed that was still true (only for the time the night circuit would switch over, not for the tariff).

Bulb say they’re having a deeper look into it for me to see if they can do anything to sync it up.