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Maximum Demand / ENA / EV Help!

D4G
Hello all,


This evenings issue relates to an EV charger install.

The supply cut out is labelled 60/80 amp so I called the DNO and asked if this could be uprated to 100 amp.

They have sent me the ENA EV application form which asks for the Maximum Demand including the new equipment.

The problem I have is the existing circuits are:


32A - 7.2 kW shower 

40A - 8.2 kW shower

32A - Ring main

32A - 7.9 kw cooker

6A - lighting

6A - lighting

6A - security


Additional 32A for EV charger


So even with diversity I'm way over 100A, obviously in reality the diversity calculations are not appropriate as the client has never blown the cut out.

The smaller shower is not currently in use although they want to replace it for another one, I have told them this may not be possible.

The EV charger will have load management but I still need to put a figure on the ENA form....


Help appriciated :)
  • 0
    It will not be the DNO ADMD - that is pretty much the one that matches the leccy bill and is the 1 to 2kw or whatever that the load averages out to smoothed over a few days.

    They want max demand - in  the sense that this is the current that may flow for up to half an hour or so when the worst reasonably credible combination of loads is in use, so they can set their fuse and tails side accordingly, and also so they can panic when more than a certain fraction of houses on the same substation request a similar supply upgrade.

    Is the form asking for amps, or kVA ?


    Or you could turn on all the lights and run the showers and put a few rings on the cooker,  and stick a clamp meter over the live meter tail.

    The thing to realise is that the on-site guide approach to diversity is not really the right thing for this purpose.

    M.
  • 0
    Chris Pearson:

    On the face of it, you have a problem because you have revealed your intention to install an EVCP, rather than just doing it. Good for you!

     


    It is part of the OZEV grant conditions to inform the DNO


  • 0
    mapj1:


    Is the form asking for amps, or kVA ?


    M.


    The question is 'Maximum demand of premises including proposed installation, concluded from a load survey, as well as any import or load limiting devices'


    .............Amps (per phase - whole current metered only)

    .............kVA (CT metered only)


  • 0
    If an OZEV grant is involved, the grant is paid to the installer. (this from https://www.gov.uk/government/publications/customer-guidance-electric-vehicle-homecharge-scheme/electric-vehicle-homecharge-scheme-guidance-for-customers ) Therefore should this figure be calculated/provided by the installer as part their job? My understanding being that an additional qualification is required to be able to install EV chargers?

    Clive

  • 0
    I imagine it is "whole current" metering, (i.e. the cables from the service head take the full current  through the meter as fat tails, rather than there being a coupler in a big bus bar chamber and a thinner telemetery  cable to a meter some distance away. CT == Current transformer - a way of measuring a 0-500A load with a 0-5 A meter ?)

    So time to sharpen the pencil, and write any credible number of amps in the box - the exact value you write will not alter the outcome, unless you ask either for more than 100A, or for 3 phases,  at which point for either of those the street gets dug up, or less than 60, when they will decide not to upgrade the fuse.

    Mike.

  • 0
    mapj1:

    It will not be the DNO ADMD - that is pretty much the one that matches the leccy bill and is the 1 to 2kw or whatever that the load averages out to smoothed over a few days.


    Yes, but SSE allowed me up to 30 kVA ADMD "for the entire development". Perhaps they thought that I was going to build a few houses instead of a garage extension. ?


    Or perhaps a garage extension is presumed to have an EVCP, which seems to gobble up more leccy than everything else put together.


    In this document ADMD is explained at section 3 (page 5 onwards) and MD is explained on page 8.


    I must say that those annual consumption figures could be a bit eye-watering. 1000 x EVCP rating in kW. If you have only a 7 kW single phase one, that would be 7000 kWh per year with an assumed mileage @ 4 miles to the kWh of 28000 miles. And if you have a Tesla-style 3-phase EVCP, how could you possibly manage 84000 miles in a year? That's 230 miles per day, every day, with no topping up elsewhere! ?


  • Former Community Member
    0 Former Community Member
    D4G:

    Agreed but I still need to put a number on the form though??


    Can you not get them to actually clarify what fuse is in there first, ie is it already 100amps, if not get it up rated to 100amps, then a decent ev charger as already stated with load curtailment feature and put the EV to charge later in the evening ie between maybe 21:00 - 04:00, this would still give plenty of time ie 7 hours if battery needed a long charge, and chances are they will not be using much load from the rest of the house. 


  • 0
    D4G


    You have to notify the ENA if your MD will go over 50A and they will notify the DNO.


    The best way to verify your MD is not by calculation but power logging the supply over a week. either using a power logger or a recording clamp meter that will last a week on the battery and will not automaticay turn off after a set period.


    Having established your MD add the EV demand and you have your new MD. With a 60A main fuse you are going to need load curtailment or s supply upgrade.
  • 0
    If only if the whole problem were that simple. The DNOs appear to have given up and are probably waiting for the World to end. If all cars were replaced with Electric (Government Policy) the electricity supply will simply fail, become extremely unreliable for everyone, but not due to the DNO! There will be a lot of houses on each distribution cable in the street, and depending on the size a modest-sized fuse of 300, 400, or 600A. These blow fairly quickly at 50% overcurrent, depriving many houses of power, and it takes a significant time to get them changed. The same failure will then happen again, so the DNO will switch off half the "Smart meters" to prevent the fuse from blowing. This is the plan, and in time each circuit will be monitored and this turning off will become automatic! Now, what happens? Britain loses its 1st World status and turns into something like certain countries in Africa. Water supplies will become unreliable because pumps will be turned off, the same with drainage. Disease will increase. By now you all realise that this is an impossible situation. However, there does not seem to be an alternative plan with any possibility of it working. Today there are light winds and we are not getting many renewables. Why do Politicians not listen to Engineers?


    As to the answer to the original OP. I suggest you tell the people not to have a smart meter, and to carry on as long as they can. If the fuse blows, you wait a bit and get a new one fitted. It will not be that long before Amazon or Ebay will have solid links available! Then the disasters will really start, thank goodness for diversity.
  • 0
    Therefore should this figure be calculated/provided by the installer as part their job? My understanding being that an additional qualification is required to be able to install EV chargers?

    Clive

     


    Yes, there is lots of criteria for successful OZEV approval,  all of which I have passed. Yes it is my job as the installer to provide that figure. I was just asking the question as to how I should come up with that figure as the regs diversity calculation is not suitable. 


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