Finally got round to doing this after 8 months with two EVs and only one charge point. The ChargeMaster is 4 years old. Ohme installed a couple of days ago. Charged both cars last night and no sign of the house exploding so that's all good... 
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Double home charging points
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We're the same, have had two charge points for a few years now. We pretty much always charge the cars overnight, at the cheap rate, and have had both on charge at the same time once or twice. It's no big deal, really, and frankly I think that 99% of the fuss made about it is from installers who can't be arsed to take the time to assess the actual max demand at the house.
FWIW, if anyone does have a marginal situation, with regard to maximum demand, it's very easy to just total load limit, either using one of the charge points that has this, or by just fitting a priority relay in the connection box. The latter is a dead easy fix that doesn't cost a great deal of money, and works even with dumb charge points (or smart ones that go dumb because the tech driving them falls over).
FWIW, if anyone does have a marginal situation, with regard to maximum demand, it's very easy to just total load limit, either using one of the charge points that has this, or by just fitting a priority relay in the connection box. The latter is a dead easy fix that doesn't cost a great deal of money, and works even with dumb charge points (or smart ones that go dumb because the tech driving them falls over).
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Alas, exploding houses seldom give any warning !Charged both cars last night and no sign of the house exploding so that's all good...
This was all properly done, the DNO and installer etc all know two points fitted. 100A main fuse of course. We could still blow that if we deliberately tried ... all kitchen appliances on, 3x elec heaters, heated floors, 2 EVs plus a 9kW electric shower would be > 120A. So I won't try that
Reality is that the cars go 01:30 - 06:30 in my Go Faster 5.5p window and nothing much else is used at that time.
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I did mention in another thread that when I did the max demand estimate on our installation, prior to installing the second charge point, we had loads of headroom. Our house is all-electric (no gas, oil or solid fuel), and in winter the hot water and heating run at night, during the off-peak period. Even with the heating on, the hot water on, the active heat recovery ventilation system on, and both charge points running we still have around 4 kW of spare capacity (we're also on a 100 A fused single phase supply).
Yet we still regularly hear of people being told they need to get their supply upgraded just to fit a single charge point. I remain convinced that most of this is just some of the big installers that have adopted a policy of not wanting to do what's required in the regs, which is to assess the total demand before doing any work involving adding a relatively heavy load, and instead they just chuck things back to the customer to sort out, getting the supply upgraded, etc.
I've probably looked at at least a couple of dozen charge point installations now, some going back 7 or 8 years, and it seems that the issue of installers refusing to do the work unless the supply is upgraded to 100 A is a relatively new thing. Around here, 80 A, sometimes 60 A, main fuses are commonplace, and I've not seen any problems with older installations with these lower capacity supplies. I did do a maximum load measurement over a period of about a week on one a couple of years ago, as they had a 60 A fused supply, but even with the car charging they never came close to the capacity of that supply. I suspect that very often this will be the case, yet it seems that few of the bigger installers would even look at fitting a charge point to an installation like this now.
Yet we still regularly hear of people being told they need to get their supply upgraded just to fit a single charge point. I remain convinced that most of this is just some of the big installers that have adopted a policy of not wanting to do what's required in the regs, which is to assess the total demand before doing any work involving adding a relatively heavy load, and instead they just chuck things back to the customer to sort out, getting the supply upgraded, etc.
I've probably looked at at least a couple of dozen charge point installations now, some going back 7 or 8 years, and it seems that the issue of installers refusing to do the work unless the supply is upgraded to 100 A is a relatively new thing. Around here, 80 A, sometimes 60 A, main fuses are commonplace, and I've not seen any problems with older installations with these lower capacity supplies. I did do a maximum load measurement over a period of about a week on one a couple of years ago, as they had a 60 A fused supply, but even with the car charging they never came close to the capacity of that supply. I suspect that very often this will be the case, yet it seems that few of the bigger installers would even look at fitting a charge point to an installation like this now.
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That's wrong. The requirement in BS7671:2018, Amendment 1 (to Section 722) does not require that the installation be TT, and there is no mandatory requirement to install an earth electrode and make the installation TT.
What the regs actually say is that there must be an adequate means of protection for an open PEN fault. That could be making the installation TT (it's what I did for our garage charge point, as it made sense) or it could mean just using some other way of protecting against an open PEN fault (which is what I did at our other charge point, ~30m from the garage one). There are several ways of doing this, using one of the open PEN fault protection devices on the supply to the unit. Some are better than others, but they all technically comply with the regs without the need to make the installation TT.
Anybody mentioned this one? HCS-D40 Dual Charging Station| Level 2 | ClipperCreek
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That's rather expensive, and I'm not sure they do a type 2 variant.
And it looks to share the 32Amp, which isn't ideal if trying to charge overnight on 'cheap fuel'
"The HCS-D40 splits electricity between two vehicles, with up to 16 Amps of electricity each when both are charging and up to 32 Amps when one vehicle is charging."
Earth rod was quoted but not required, so I was refunded the cost of it. So no, is the answer.
You won't blow the fuse. The minimum current that appears on the graph for a 100A BS88 fuse is 150A and it will hold that for 7,000 seconds (2 hours). One reason for not trying it is that drawing 120A for two hours would be expensive!This was all properly done, the DNO and installer etc all know two points fitted. 100A main fuse of course. We could still blow that if we deliberately tried ... all kitchen appliances on, 3x elec heaters, heated floors, 2 EVs plus a 9kW electric shower would be > 120A. So I won't try that
I assume from the instructions that the OHME has no internal Open PEN protection so you can understand why they have made their lives easier by mandating TT. However, in doing so, they haven't addressed the risk of inadequate separation.
Reassuring! But I still won't try to blow it
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TBH, I think they just haven't bothered to update those instructions for a year or so, at least since Amendment 1 was released. That amendment clarified the use of devices that monitored voltage as a way of detecting an open PEN fault (not that I think that's particularly safe).
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Closest to 30 A would be be a 32 A commando outlet, as there's no 30 A rated connector in common use. Installing a 32 A commando would incur the same costs as installing a charge point, as exactly the same provisions in the regs need to be met and the work involved would be identical. The only difference would be that an interlocked 32 A commando outlet (and it should be an interlocked one in this case) is a fair bit cheaper than a charge point, but then you also need to factor in the cost of a suitable portable EVSE that can handle 32 A (the Ohme can, as can the Tesla UMC, plus one or two others).
Yes, thanks, I should have said 32A. I wouldn't want a smart charger, but next year, I should have 2 EVs and there may be situations when both need to be charged. It does seem unlikely though, so probably better to wait and see if a second point is needed.
I was surprised and pleased to discover that the EVSE supplied with the eTron includes an interchangeable 32A Commando tail and supports charging at 32A from a suitable socket. Interchangeable 13A tail also supplied; it's the best manufacturer-supplied EVSE I've seen.
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