Dual Rate Meters — Bulb Community

Dual Rate Meters

There are two ways to connect a meter to give cheap rate electricity overnight. (For example, to charge an EV).
A) All circuits in the house are connected to a single output of a dual-rate meter, which charges a reduced rate for 7 hours overnight.
B) The circuits in the house are split into two independent groups, connected to two outputs of the meter. The overnight group can only be used during reduced rate time (and cannot therefore charge a vehicle during the day). The 24 hour group always charges the full rate.
Other suppliers offer both methods and Bulb have offered 'A' which is what an EV driver needs. The engineer who comes out to fit the meter only understands 'B' which is not only useless but not what I was anticipating.
Do any other Bulb customers have setup 'A' working?
Do any other Bulb customers charge an EV at home?
It would be helpful to know. Thanks.

Comments

  • 'B )' has been turned into an emoji with sunglasses. It should just be the letter.
  • edited December 2018
    I'm currently on the Bulb time-of-use smart tariff beta trial. This uses a smart meter to bill at 3 different rates:

    https://bulb.co.uk/smart/

    There are no dedicated circuits. There is just one output from the meter, allowing for maximum user control and convenience. I charge my EV at the overnight cheap rate by making use of the in-vehicle charge timer.

    I'm afraid I can't offer any advice on the more conventional Economy-7 style configuration. Rather than trying to get an E7 meter, I'd recommend simply waiting for Bulb to roll out their smart meters from the beginning of 2019.
  • Yes I had 'A' setup, it's a simple 2 rate meter setup.
  • Well, as a retired electrical engineer I can honestly say that I've never heard of a domestic electricity supply being split into 2 separate circuits in order to achieve 'Off Peak' or 'Ecomomy 7' metering.
    The old fashioned way was to have 2 meters installed, one normal rate meter & one White or Economy 7 meter. A time switch was used to change over metering of the supply during 7 hours typically between 11:00pm & 6:00am & the time clocks wouldn't normally be altered during daylight saving.
    Smart metering means that only one meter is required & all calculations are carried out at the supplier receiving facility so that many different tariffs can be offered dependant on the time of day.
  • Well, as a retired electrical engineer I can honestly say that I've never heard of a domestic electricity supply being split into 2 separate circuits in order to achieve 'Off Peak' or 'Ecomomy 7' metering.

    As I understand it, E7 is sometimes split off onto a separate circuit so that certain devices (i.e., storage heaters) are automatically powered as soon as the E7 period starts. If there isn't a separate circuit, then everything has to have its own timer, and know the correct start and end times.
  • edited December 2018

    Well, as a retired electrical engineer I can honestly say that I've never heard of a domestic electricity supply being split into 2 separate circuits in order to achieve 'Off Peak' or 'Ecomomy 7' metering.
    The old fashioned way was to have 2 meters installed, one normal rate meter & one White or Economy 7 meter. A time switch was used to change over metering of the supply during 7 hours typically between 11:00pm & 6:00aPlem & the time clocks wouldn't normally be altered during daylight saving.
    Smart metering means that only one meter is required & all calculations are carried out at the supplier receiving facility so that many different tariffs can be offered dependant on the time of day.

    As @Hooloovoo says, it was definitely a thing..see here

  • In my experience, & I'm certainly not suggesting that you're wrong, domestic storage heaters are on the same general circuit as all the others circuits in the property but are likely to be on a time switched sub circuit so that they can be set to turn on during the 'off peak' period.
    This means that anything else that draws power during this time will be charged at the lower rate & if the storage heaters are set to boost during the day time, they will of course be metered at the higher rate.
  • In my experience, & I'm certainly not suggesting that you're wrong, domestic storage heaters are on the same general circuit as all the others circuits in the property but are likely to be on a time switched sub circuit so that they can be set to turn on during the 'off peak' period.
    This means that anything else that draws power during this time will be charged at the lower rate & if the storage heaters are set to boost during the day time, they will of course be metered at the higher rate.

    Ok. I think we're saying the same thing. I wasn't suggesting that there is a completely separate E7 supply to the house.
  • This is very helpful, thanks. Now I know that what I'm asking for is not only possible but actually the norm.
    My first experience of reduced rate electrical energy was in 1967 when our house had underfloor electrical heating. It could only be used overnight - no way to turn it on during the day. The "white meter" had a separate distribution board.
    My present arrangement is the 100A fuse at the front door with the distribution board 2 metres away on the other side of a wall. The engineer is asking for a separate distribution board to be installed next to the meter so that he can connect two separate cables from the meter.
    My car will decide when to charge itself - it is a computer on wheels basically! - so I don't need a timed circuit to control that. Should we get a second EV, the charging ports outside the house have enough intelligence to ensure that both cars don't try to grab 30A each at the same time.
  • edited December 2018
    John_Mac said:

    My present arrangement is the 100A fuse at the front door with the distribution board 2 metres away on the other side of a wall. The engineer is asking for a separate distribution board to be installed next to the meter so that he can connect two separate cables from the meter.

    Yeah, he just needs to leave the second switched output disconnected since you wont be using it. If he really insists, I suppose you could always have the switched E7 distribution board installed and then just not have any final circuits installed in it!

    Depending on your configuration, your EVSE could require its own distribution board anyway due to the requirement of a type-A RCD. Typically the configuration is a dedicated CU that is either fed from a non-RCD high-integrity MCB in the main CU, or fed directly off the meter tails split with a Henley block. So the arrangement of your existing CUs and whether or not that is a switched CU for E7 is kinda irrelevant. It sounds like your meter installer can't handle anything even vaguely non-standard so his head will probably spin if you try to introduce this extra complication.

    I'm actually surprised the meter installer is even asking about this, since it's not in their remit to be installing any distribution boards. They are only responsible for the tails from the cut-out to the meter. The output from the meter and anything after that is the consumers responsibility (hence the name consumer units). The installer is probably just bothered that he doesn't have a second cable to connect to the switched meter output.
    John_Mac said:

    My car will decide when to charge itself - it is a computer on wheels basically! - so I don't need a timed circuit to control that. Should we get a second EV, the charging ports outside the house have enough intelligence to ensure that both cars don't try to grab 30A each at the same time.

    What EVSE are you getting? I think right now only the Tesla EVSE can handle load balancing between two or more wallboxes. I know PodPoint are also working on load balancing but I don't think they have that rolled out yet. Perhaps you can afford two Teslas =)
  • I think @mowcius might be able to help here?
  • edited December 2018
    @John_Mac, who is trying to install this meter and why?

    Pretty sure the smart meters that we'll get from Bulb will be the ES-10A or ES-10B, which both have a main 100A relay and then a secondary low current relay for ALCS functions (which could be used with a contactor to switch a heating circuit I suppose).
    EDMI do make an ES-12B now which has dual 100A relays, but I can't see Bulb installing those for everyone as most installations would not use the secondary output now everything's becoming smart.

    I'd have thought that the meter installer would just cap off the unused outputs in your case - you can always pay to have an installer come back in the future to connect up some new tails if you had a second rate CU installed.
    The meter should still switch rates based on time on the main output, whether or not you're using the secondary output.

    For two car chargers I'd expect a secondary consumer unit, which would either be split off the meter tails if in close proximity, or from a breaker in the main consumer unit if much further away.
  • Hooloovoo said:

    Perhaps you can afford two Teslas

    Electric underfloor heating in 1967 - perhaps they can :mrgreen:

  • It can definitely be done, my 2007-built flat has one of its immersion heaters connected to the night-time circuit only, the other one is on 24/7.
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