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Electric boilers - effect on power demand of a block of flats

donf
Hello there.


I would like to  know if anyone on the forum has done a study of or knows about an existing study of the impact on power demand of introducing electric boilers to block of flats. 


I have been tasked with estimating the impact of a gradual migration to electric boilers for central and water heating in a modern block of flats. Nearly all of the flats currently use gas fired combi boilers.


I then have to present this information to UK Power Networks so that they can asses whether or not an increase in capacity to the building supply might be needed in future.  Finally I need to put any recommendations to the owners' management board.


Clearly electric boilers will have some impact on power demand.


I can start with an estimate of current power demand (worst case) for a typical flat.  To that end, I'll be doing a survey of about 25% of the flats to come up with a figure.


I can then apply the IET Electrical Installation Design Guide diversity calculations for a typical flat and then the building as a whole using figure 3.4 (IET Electrical Design Guide Nov 2008 page 33).


I can then do a second power consumption exercise adding the demand of a typical electric boiler per flat and then the whole building.


However, it's not clear to me if this approach will be suitable for a massive migration to electric boilers.  I need to be sure of my ground if I approach UK Power Networks with a demand figure.


If we look at the usual peak use of heating demand (morning and evening) a building full of electric boilers, to me, could add a significant load to existing street fuses and possibly even cable capacity.


I would be grateful for any suggestions and experience people could bring.


Kind regards


donf










  • 0
    The ones I have had experience of are 2 x 11kW heaters on the wet heating/hot water system with cylinder storage, each on 16mm and 50 amp OPD each, using off peak and normal tariff. Economy 10 I think it was was then. Perhaps 6 or 7 years ago. One big deal is keeping the final circuits short and near the Origin, due to excessive voltage drop locking the things out. Could be a real challenge for Flats that are some distance from an origin on the ground floor.
  • 0

    It's an interesting question because at some stage gas boilers will become a thing of the past.



    Really that's got to be tackled by far better thermal insulation. Current building regs and double glazing are still chickenfeed compared with what's possible/needed. Even a decent sized detached house to PassivHaus standards can be space heated perfectly adequately on about 2kW - and then only on the coldest days. At those sort of levels electrical heating becomes both practical and affordable.


       - Andy.
  • 0

    a number are induction hobs  - any thoughts on diversity for them??



    Same as for any other cooking appliance. If anything they're a little more efficient than traditional resistive hobs, so a little more diversity (lower overall load) might be justified, but treating them the same as the old ones errs on the safe side.


      - Andy.
  • 0
    I maintain a few houses with an electric boiler.

    The boiler is 10kW. It is only used for the radiators.

    They also have a water tank with one or two immersion heaters.

    The houses are quite warm when running, though the running costs are rather more than you would like to pay yourself.

    We also have a number of air source heat pumps in communal flats.

    When running well, they run both the heating and hot water. They run off a 16A supply.

    Typical running costs in the winter are £40+ per week. My gas boiler is £40 a month.


    I think electric boilers would be a very poor choice for heating and hot water, Air or Ground source would be far better, with cheaper running costs, albeit a larger installation cost.

  • 0
    Hi Alcomax


    Well, that will go down well.


    In these flats, the distribution board is usually some distance away from the existing boiler position.


    The flats are generally expensively fitted out and finished.


    Then I walk in and tell them that I'll be running 16mm (possibly even bigger if I heed your take on cable voltage drop) across the flat.  They will have large trunking (imagine chasing!) from one end of the flat to the other.  Not to mention finding space for a separate fused isolator in what is usually a small hallway cupboard.


    Splendid!



    donf


  • 0

    Posted by Chris Pearson on Feb 27, 2020 5:38 pm



    It's an interesting question because at some stage gas boilers will become a thing of the past.


    True, but right now, one of the biggest users of gas is burning it to generate electricity.  Yes an electric heater  is 100% efficient. But then a modern boiler is pretty good,  our 15 year old 22kW one puts out something about the warmth of a horse breathing on your hand.

    The gas turbine power station is perhaps 50% efficient from gas to electricity, and then there is distribution, transmission etc. There is  a very good reason gas is 30% of the price of leccy per kW.

    Also while better insulated housing will help, I reckon 3/4 of the  buildings we will inhabit by 2050, the zero carbon date, are already built. We will have a slightly titivated version of what we have now, unless there is a massive housing demolition campaign, and if there is, then questions about existing boilers will be moot.




  • 0
    I think this is an extremely bad idea. There is simply not enough electricity available for many people to have fully electric heating. The investment necessary to make this work is at least 2 trillion pounds external to buildings and probably another 100 billion for house owners. Typical gas boiler installations are much more than a couple of kW, and without replacing ALL the housing stock (cost at least 10 trillion pounds) there is no way to make this work at all. My house (3 bed semi from 30s) has a 20kW central heating boiler and a 20 kW hot water boiler (instantaneous) which gives good heating and showers / baths. Heating efficiency is > 90%. Ok I need 20 kW a lot and 40 kW max demand, the electrical infrastructure cannot give this so ??????


    Unfortunately CO2 is not warming the atmosphere, and global warming is due to natural variation and very small (1 degree C per centuary) so I suggest you simply say it is not possible. Add an electric car and the supply system is st***ed, so the where are we? Britain is about 1.5% of global heating, what about the rest? Even if we believe the doomsayers, we can only prevent about 20 milli-degrees of warming whatever we do! Good idea, NO.
  • Former Community Member
    0 Former Community Member
    I got involved 10 years ago on a site of a dozen 2, 3 and 4 bed new build houses aimed at retirees where mains gas wasn't available and the "developer" went all electric with "wet" central heating due to the dislike of night store and didn't declare this form of heating to the DNO..............

    The particular brand of boiler was installed in units of 6 and 9 kW, the smallest house on 9 kW and by permutations, 12 kW, 15 kW and 18 kW. It initially ran ok but as winter approached, several of the circuit boards "died" as they were designed to trip out should their terminal voltage fall below 207 V and at £200+ a "pop" were initially replaced under guarantee but the issue persisted, hence my involvement. I left a voltage recorder in one and it confirmed voltages below 207 V.

    The reason for the time for the "fault" to manifest itself was due to one homeowner signing up for "economy 10" or similar which gave a lunchtime 2 hour boost, during which, once the word spread and all the retirees signed up, everyone took advantage of the cheaper rate and did their cooking, washing etc at the same time the boiler kicked in..............

    The DNO went after the developer to recoup the £100k it cost to upgrade both the HV and LV network (it was very rural, hence no mains gas) as he hadn't applied for the correct demand but like most developers, he'd formed a Ltd company just for that site and then folded it............

    So, it may not be just the heating load that needs consideration, but the real possibility of economy 10 etc being "abused". Bring back the white meter I say!


    Regards


    BOD
  • 0
    If these electric boilers are connected to any thermal storage, and utilise economy 10 or any other similar tariff, then I would argue that no diversity whatsoever is allowable. It is a reasonable expectation, that every single boiler will run at the start of the off peak tarrif and will heat up the thermal store.


    10Kw per boiler, only 40 flats is half a megawatt after allowing for other loads being concentrated at the same time.
  • 0

    davezawadi:

    I think this is an extremely bad idea. There is simply not enough electricity available for many people to have fully electric heating.




    Quite so! We use gas for cooking and heating - leccy is about 8% of our energy consumption.


    It's all very well for the politicians to announce that gas appliances and internal combustion engines will be banned within the next 20 - 30 years, but they appear to ...


    (how shall I put this politely?)


    ... to have been badly briefed. ?

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