SOT: 3 phase supply

How many kW of AC will the particular car take? DC charging will be a different number.

I believe it's 11 kW which AIUI is above the single phase limit but not to the point of justifying major expenditure. If the suggestion that I have three phase already is correct, I might as well take a look. I believe there is no additional unit charge for the electricity.

There's no suggestion of 3-phase in your description. Just fuses which have been update to newer specifications without the non-compliant being removed.

Oh, and fuses are rated in amperes, not watts.

A photo would help a lot

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I think you are misreading. It's probably 100 Amps (not watts),. This house has a similar input configuration - but only 2 of the phases has an input.

Yes, that'll be 3ph at 16A. As you say, above the max for 1ph at 32A which is 7kW.

Sorry, I should have said 100 amps and 60 amps. All three fuses are identical, but just one is wired. It is clear they were installed at the same time. I'll see if I can get a photo, as The Nomad suggests. I understand this does not mean the incoming supply is three phase but I wonder if there is a way of checking.

Absolutely, 100 amps. The DNO person said the maximum is 80 amps but I think she was mistaken. How does yours work? Does your house have two phases in different parts or is the second phase for another purpose?

To me it sounds like a 3 phase supply cutout but a single phase meter. Some pictures of a similar setup is here:

However, a three phase supply is overthinking it for a single EV. Most EVs will charge at 7kW on single phase and 11kW on three phase, so not a great difference in charging speed.

Suppose you bought a typical EV with a 60kWh battery. On a good day you might get 4 miles per kWh so it's good for 240 miles of range. If you arrive home after having done a 240 mile journey with the battery completely empty, it'll take 8.5 hours to fully recharge on 7kW and 5.5 hours on 11kW.

In reality, you're likely to plug the car in every time you get home so it's full by morning. Most of the time you're probably doing local journeys which are a few tens of miles - easy to refill in a couple of hours, so the supply current isn't a big deal.

There are some cases where having a beefy supply makes sense:

1. Where you do a lot of miles every day - say you're a taxi or delivery driver
2. Where you're driving a very inefficient EV like a brick-shaped delivery van (which gets more like 2 miles/kWh)
3. Where you have multiple EVs in the household which are heavily used most days, ie a house with 3/4/5 drivers all doing dozens of miles every day.
4. Where you want to make best use of a low-rate tariff for a few hours a night (cheap rate charging for 4-5 hours overnight) and you do a lot of miles (eg in cases 1-3).
5. Where you have additional hungry loads, eg heated swimming pool (ephemeral things like electric showers don't count because they only run for a few minutes and they can be arranged to load-shed the EV charger for the duration)
6. You have a big solar array and want to make use of every drop of solar generated during sunny times

Most people who just do a dozen miles to work and a dozen miles home every day don't really need even 7kW: 24 miles is 6kWh and you can get that in a few hours on a 13A plug.

Theo

DNOs have decided to reduce the maximum current for houses to 80 amps on a single phase. Historically a lot of houses were upgraded to 100 amps in the past but this has now stopped I believe.

So, if you ask the DNO, they will say that 80 is the maximum. Unless they have a good reason to I imagine it would be very unlikely that they would downgrade an existing 100 amp fuse for an 80 amp one though unless they happened to be in your house pulling the main fuse for another reason.

Maybe worth getting an 80 amp sticker and putting it on the fuse holder? ;-)

Tim

remove the seals and then remove the fuse holder and use a voltmeter. Not that you should.

ICBW but it's my impression that there is a much higher standing charge for a 3-phase supply even if the unit rate is the same.

In theory, with a 3-phase 32 amp supply, you could charge at 22kW but if the vehicle can't take more than 11kW fron an AC supply (much more from DC of course), there doesn't seem all that much point of adding the complication of a 3-phase supply. It would be a bit faster but would still take several hours - so if you're charging overnight you won't notice the difference.

Three-phase: £2,000+ per year, including: ...

Looks like a good business to be in.

A charge like that, would not deter Bill Gates.

But even Bill Gates has changed his ride, for a laugh. He'll be fiddling around with the fuse on his home-made cable.

Interestingly, only one of them is sealed. Does this answer the question? Alternatively I could offer to buy my friend who is a retired electrical engineer from Scottish Power a curry. I just thought it might be possible to check via the MPAN number.

Interesting ... I knew about the upgrade but not the downgrade.

About a year ago I think.

Like yours, ours was upgraded to 100amps when we had our EV charger fitted (5 years ago). I see from other groups that this is no longer happening and folk are being told that 80 is now the norm.

In practice this won’t affect too many people at present.

Tim

But what is the point of this? What has changed from two years ago?

Is this national policy or did one DNO decide to do it? I can see Northern Powergrid did:

I'd have thought this would be right PITA for diversity calculations, which assume worst case loading. The above doesn't say what max current should be used for that, so I think we have to assume 80A unless told otherwise.

Theo

Historically domestic and small commercial connections that have been provided to customers may have incorporated a cutout fused at 100A. This was deemed acceptable where the installation was terminated within an area where the temperature was less than 20°C during the peak demand period and where the earth fault loop impedance was no greater than 0.38 ohms. Although the fuse had a nominal rating of 100 amps, customers would seldom consume a power level near the maximum permitted and would typically have a much lower load.

However, with the inclusion of low carbon technology where the load profile is moving from ‘cyclic’ to ‘sustained’ and where the peak power consumption has moved from the winter to any season. NGED has made the decision to reduce the fuse size installed within domestic style cutouts to ensure that the current flow is restricted to within the thermal capacity of the installed equipment.

John