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2 electricity supplies to one building

Former Community Member
Former Community Member
Hello, I am a not an engineer but need some advice on uk wiring regulations please. 

A national utility company is fitting a 32A charger in my garage for an electric vehicle. 

The garage is detached from my house but there is an existing circuit from the house consumer unit to the garage for lighting and a power socket. The cable runs along a garden wall. 

The new charger will have its own cable run from the same consumer unit in the house down to the garage. 

My problem is that the engineer who came to do the installation refused to do it as he said the garage is a building in its own right and regulations do not allow 2 supplies to one building.

My question is: Do 2 wiring circuits from the same consumer unit constitute 2 supplies If the consumer unit is located in an adjacent building? 

I would have thought that this was still a single supply and to have 2 supplies you need 2 separate meters with 2 consumer units which is not the case here but then, as I said, I’m no engineer. 

Edit.....The engineer stated that the regulation related to avoiding the risk of a voltage between 2 different earths. To me this again only makes sense if you were talking about 2 totally different supplies from different meters and therefore possibly different sub stations etc.
  • 0
    davezawadi (David Stone):

    Hi Simon


    Do you really believe this is the future of electricity? It would be nice if you answer this because when the electrical collapse occurs, it is unlikely that BS7671 will have any relevance any more, people will be dying in droves.


     


    Yes I do.  And coming up with ridiculous figures like £30 million in subsidies per car isn't helping anything.


    We would already have electric trucks trundling up and down our roads, if it weren't for a global shortage of batteries.  The savings on diesel fuel would be so huge as to make electric trucks a no-brainer for anything but the longest of journeys.  The drivers have to take breaks every few hours, so all we need is chargers at every truck stop and the limited range isn't such a problem.


    I can tell you really want to keep things just the way they are, and so all you can do is to find reasons why it's too difficult to change.


  • Former Community Member
    0 Former Community Member
    The drivers have to take breaks every few hours, so all we need is chargers at every truck stop and the limited range isn't such a problem.


    4.5 hours actually. followed by a 45 minute break. 4.5 hours at 56 mph (often nearer 59 mph as the tractor unit gets fitted with just legal drive axle tyres when speed limiter is set) gives around 250 miles.


    I'll let someone else do the figures for this!


    Regards


    BOD
  • 0
    I think that is being unfair.

    Here are the numbers. 40 million cars 10 million trucks and vans. so 50 million, the trucks and vans need an extra charge factor of 5 on average, which I feel is fair, so 90 million charge units.

    Cost 3 trillion pounds, some for heat pumps so let's say 2.7 trillion.

    90 million * £30 million = 2.7 trillion. That looks awfully accurate to me.

    How long do you think road tax and fuel duty for electric will stay at zero? In a big truck, they amount to around 80p per mile, so the same for electric lorries, with the price of electricity as it saves (no costs) around 20 pence a mile more than diesel. What you are failing to appreciate is that diesel is a very cheap and energy-dense fuel, and the retail price of electricity is very high compared to other forms of energy. I am also waiting to see the truck battery being charged at 2 MW for an hour rest (not needed with 2 drivers remember) because that is the energy that could be used in the next 4-5 hours. If battery charging is 90% efficient, that battery loses 200kW as heat, during charge, now that could be interesting as it would need to be spread throughout the load space unless there was a lot of forced air cooling equipment as well. This truck certainly has zero load capacity. Tesla hasn't had much luck with heavy trucks, lots of PR though. Services with 50 truck chargers might take 100MW, now that is quite impressive, more new EHV lines then and big transformers. Do you really think these are free? In the US, cross-state trucking is very common, and the rules are less prescriptive. Fuel is even cheaper than electricity. The case to do so is very poor.
  • 0
    The HGV speed limit on motorways is actually 60 MPH BOD. The owners like a bit less for fuel consumption reasons.
  • 0
    We would already have electric trucks trundling up and down our roads, if it weren't for a global shortage of batteries. 

    Not really,.

    There are already enough batteries to make a few million electric trucks, and that would be a small start, (UK alone has about 4 million small lorries and about half a million HGV on the roads each working day, and we send quite a lot by train.) but if we did ,then the next bottleneck is the (total lack of ) ability to re-charge them.

    It can and will eventually be done, but phased in over several decades as oil runs out, but not quickly and certainly not cheaply.


    Have you seen the electric charging requirements for a typical electric HGV yet ? That one is 22kW for the 10 hour  'slow charge' built in, and 150kw for 40 minute fast charging (for a range of 90 odd  miles after a - so recharge after something like  90 mins on the motorway. Normally drivers stop after more like 4 hours.)

    Something like Eddie Stobart's modest fleet of 2700 'artic' vehicles will need a sizeable chunk of a power station. (at the moment they have more trailers than tractor units, with electric that ratio may change.)

    And remember we are supposed to be phasing out natural gas for heating and cooking over the same period, so the demand will rise from two directions.

    Mike.

  • Former Community Member
    0 Former Community Member

    The HGV speed limit on motorways is actually 60 MPH BOD. The owners like a bit less for fuel consumption reasons.


    I think you missed my legal point there Dave! And that the drivers deliberately fit just legal tyres for the speed limiter to be set to with the intent on going faster than 56mph when normal treaded tyres get re-fitted so not driving for economy, but outright speed.


    Regards


    BOD


    PS. Apologies for font but couldn't see a way to alter.




    Speed limiters



    A speed limiter must be fitted on:



    • vehicles with more than 8 passenger seats, eg buses, minibuses, coaches, stretch limousines

    • goods vehicles with a maximum laden weight of more than 3.5 tonnes

    Speed limiters are designed to reduce accidents. They limit the maximum speed of a vehicle by restricting the fuel supply to the engine. Having a speed limiter may mean that your vehicle can’t reach the speed limit.


    New vehicles Goods vehicles with a design weight over 3.5 tonnes and buses with more than 8 passenger seats (regardless of weight) registered on or after 1 January 2005, will be required to be fitted with a road speed limiter. The limiter will restrict the maximum powered speed to 56mph (90km/h) for goods vehicles, and 62mph (100km/h) for buses. A speed limiter will not be required until 1 January 2008, however for vehicles used solely on UK journeys and are either: • a goods vehicle with a design weight not exceeding 7.5 tonnes, or; • a bus with a design weight not exceeding 5 tonnes New Speed Limiter Legislation V2.qxd 12/7/04 1:04 PM Page 2 Older vehicles Vehicles registered between 1 October 2001 and 31 December 2004 (inclusive), will also need a road speed limiter if they are: • a diesel engined goods vehicle with a design weight over 3.5 tonnes, but not exceeding 12 tonnes, or; • a diesel engined bus fitted with more than 8 passenger


  • 0
    davezawadi (David Stone):

    90 million * £30 million = 2.7 trillion. That looks awfully accurate to me.


    You're only out by a factor of 1000 :-). The result of that multiplication is 2700 trillion (assuming the modern usage that million = 1E6, billion = 1E9, trillion = 1E12)


  • Former Community Member
    0 Former Community Member
    Just to throw another one in here, where do you think the lost revenue from tax on road fuel will come from?


    As I've banged on about previously, I can see smart meters having half hourly rates to reflect "grid cost" both during low demand where Octopus posted it was free for 31 periods last year but would cap at 35p/kWh to beta uptake consumers.


    I can also see Authorised Supply Capacity being introduced as well as grid matched p/kWh for installs less than 69 kVA so that those who want to rapid charge their EV, pay for the privilege of National Grid keeping spinning reserve of the less efficient power stations just for their demand.


    Out of interest, how is France coping with domestic supplies limited to 30 A single-phase and EV charging?


    Regards


    BOD
  • 0
    Well done Wally so it does, very foolish of me, obviously, I didn't count the 0s on my calculator correctly! So that is £30,000 per charge unit, which does not sound quite so bad, but is still totally unreasonable, and thinking about it does not sound enough. In fact, it is slightly different, £30,000 for every domestic property in the UK, and loads more for the trucks and Motorway services. To do this £3,000 needs to be added to every domestic electricity bill, every year for the next 10 years. Still politically totally impossible, 75 percent of households would not be able to afford it! It cannot be suggested that borrowing the money is sensible either, a depreciation rate of 10% PA may be a little high, but still, the money could never be collected back from consumers. One can see why Germany is struggling with electricity prices.
  • 0
    That is a point I suppose BOD, but the difference between 56 and 60 MPH is not going to reduce accidents significantly. True tyre wear does make a slight difference, but the big problem is lorries in lane 2 going at the same speed as those in lane 1 and blocking cars! I have evn seen 3 doing it on 4 lane sections. This  needs a change in the law, because it both common and daft. On a downhill bit the more loaded lorry picks up a bit more speed and eventually gets past, saving him 30 seconds on the journney.

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