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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
    Nikp:
    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. 




    Even if I find out, the ENA form still needs to be filled in as part of the grant process. 


  • 0
    John Peckham:

    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.


    60a is the figure, if below 60 then you can notify DNO after installation but if above 60 then you should notify before installation. 


    Logging the consumption is the answer but not so practical and I doubt a common practice being as customers want answers today! 


    I believe the norm is to request a 100a upgrade before EVSE installation, this is what I asked for when was presented with the ENA form. 


  • 0
    Chris Pearson:

    <SNIP>

    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.


     




    well 130A for short periods (30,000/230V) seems a safe limit if you have 100A fuse, you wont exceed that for more than perhaps 20 minutes. !!!!

    That link is interesting, Western power seem to have a different method to some of the other DNOs

    I agree on the annual consumption estimates.looking rather  high. I suspect there is not enough real data yet to allow then to do anything other than  bung in a large number and hope it is enough, or maybe they are expecting or hoping to encourage that most home charge points end up being  the 10-20A sort of range, not the 7Kw 32A ones - after all they do not meter at the street or town level and much domestic metering is averages over a long period, not half hourly


    I think DZs predictions are a bit dramatic - but only because I predict that the forecast numbers  for electric cars by 2030 will be missed, and substantially, except perhaps in cities like London,  and that once a few substations have caught fire, the govt will need to be tapped up for a street main renewal scheme to rival that of the removal of cast iron from the underground  gas network.

    Right now the govt is only vaguely aware of the can of worms they have opened ( pages 43-45 of this policy exchange docuement scratch the surface)


    M.

    PS to DG4, I think we all agree you want a 100A fuse fitting. The network that supplies it is luckily not your problem.


  • 0
    mapj1:

    well 130A for short periods (30,000/230V) seems a safe limit if you have 100A fuse, you wont exceed that for more than perhaps 20 minutes. !!!!


    Ah, but there are 3 fuses. ?


  • 0
    The document you cite Mike is slightly interesting but hopelessly badly informed.  If the Government is reading stuff like that it is not surprising they are upbeat about electric vehicles. Where I live most houses have 2 vehicles, some have 4 or 5. Many houses probably have maximum demands like the OP. Interestingly very few have charge points. I would be quite surprised if the local substation could handle another 250 kVA, even at night, and it feeds around 1000 houses. We shall see what happens, but given some of the recent news, I suspect we are heading for supply problems. I think that the next big shock will be the level of tax for electric vehicles once they become a significant proportion of vehicles. Interesting times ahead!
  • 0
    Of course the DNO will have to consider if they have any spare capacity on the local transformer. It could be they have sold or the capacity on the transformer and they will refuse the additional supply.
  • Former Community Member
    0 Former Community Member
    the govt will need to be tapped up for a street main renewal scheme to rival that of the removal of cast iron from the underground  gas network.


    As far as I can tell the DNOs are largely sitting back waiting for this to happen, just getting ready to say "look we tried, but now you need to pay us to fix it". They know that ultimately the government will have no choice but to pay for serious LV network reinforcement. Expensive mitigations using their own money now are just not good business sense, even if that avoids digging everything up in a few years time. New housing estates are still being built with load assumptions that are looking ever more dubious as time goes on.


    Am I being too cynical here?


    WPD offering new supplies as 3 phase by default is a good start, but so far as I am aware they are the only ones?


  • 0
    It is for engineers to design systems and for the Boris Brigade to beggar it all up. The polotics are all experts in their chosen field and worked comprehensively on the Peter Principle. No matter which party they will successfully beggar it up
  • 0
    If you make the rough assumptions that the total mileage of each household is 10,000 miles per year and that EVs do about 5 miles per kWh, then the existing domestic infrastructure can just about cope as long as cars are given a slow 7 hour-ish charge each night when the local network would otherwise be mostly unused. That works out at about 3.5A per house.


    This does of course require smart chargers talking to smart meters so that the consumer plugs in their car when arriving home from work, and presses one of two buttons: (a) quick charge as I'm going out in half an hour or (b) please be fully charged by next morning. For (b) the smart charger needs to know not to come on until late evening, and not to immediately turn on full  like storage heaters, but to slowly charge, varying the exact rate according to feedback from the smart meter, and hence from the substation and ultimately from the national grid.


    As far as I'm aware, smart meters and chargers don't currently do this, and there doesn't seem to be any immediate plan to make it so.


    Also, I assume separately that 400kV pylons or similar will have to feed each motorway service station to provide the equivalent of 5-minute petrol station refills for many cars.
  • Former Community Member
    0 Former Community Member
    wallywombat:

    As far as I'm aware, smart meters and chargers don't currently do this, and there doesn't seem to be any immediate plan to make it so.


    Apparently French smart meters have a standardised communications bus for this kind of thing. Where a UK demand-managed charger (or heatpump, etc.) might have a CT around the incomer a French one has a data connection to the meter.


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