Three Phase or not?

[mike2016]

Hi,

I'm thinking forward to what type of Electrical connection to apply for down the road if my self build commences. The Electrical Board in Ireland offer 12kVA for Standard Domestic and 16kVA for larger Domestic houses or ones with Heat Pumps. The reason I'm thinking of a larger supply like Three Phase is primarily for future proofing should I get an Electric Car. I would also get Night Rate Electricity so the price of charging overnight is less. if I could afford it a battery like a Tesla Powerwall 2/3 so I can offset the dearer daytime electricity would be ideal. 

 

Anyway, with three phase I could get 20kVA or 29kVA & fast charging for newer cars with their increasingly larger capacity batteries. My work travels all over the place, it's not a fixed point to point. Knowing I can fully charge at home overnight and top up in transit offsets the risk the destination has no charging facility. 

 

So, what do people have in their homes currently and is three phase the way to go or overkill? There's not that much extra cost for a new connection I've found but the site is in an existing housing estate so it may not be possible to supply the necessary current without a lot of digging (worst case)....I'd still like to know if it would be worth the trouble. 

 

There's no change to standard domestic appliances I'd assume, just a different meter/fuseboard? I would get something like a pod-point S22 capable of using the additional capacity. I'd still like to get some solar PV going but have limited roof / garden space in the design....

 

Anyway, any thoughts on Three Phase for EV Charging or other benefits of having it welcome.....Thanks!

Edited February 19, 2017 by mike2016

[Jeremy Harris]

This is something I thought long and hard about, too, for much the same reasons.  In my case, I already had to get a big three phase underground cable moved as a part of the initial site ground works, so I had it relocated so that it runs directly under the location of our external meter cabinet.  In the end I decided not to have a three phase installation, but really only because it would be fairly simple to change it later - just a matter of digging a hole to where the current underground joint is, around 2m of new cable, a new meter and switching to a three phase tariff.

 

One of the reasons I didn't fit three phase was that the price of fast charge EVSEs is very high, compared to a 32A single phase EVSE (the highest one can go with the standard J1772 / IEC 62196 cable and connectors), and few EVs seem to be able to use the three phase IEC 62196 capability in practice; many seem to just use a single phase when AC charging, or CHAdeMO (or Tesla Supercharger) for DC charging.  It looks to me as if fast AC charging isn't going to be the way EVs develop; my guess is that they will go down the Tesla Supercharger / CHAdeMO route.  So, I've got one 15A charge point and one 30A charge point, both single phase and in different parking locations.   In reality, an overnight charge at 30A is around 25 range miles per hour, so easily a couple of hundred miles overnight, perhaps a fair bit more.

[AliG]

I have gone through the same thought process.

 

I am going for three phase just for flexibility on the number of high power devices that may be used simultaneously.

 

As @JSHarris you won't need 3 phase to charge an electric car and chances are most of the charging will be during the night when you won't be using any other devices.

 

But it wouldn't take much to be using an induction hob, fast charger, ashp, oven, kettle etc all at the same time and theoretically overload the main fuse, although you would need to be running all the rings on the hob etc. So I think the thing to consider is how many items you are going to have that may require a 30amp fuse and could you be using them all simultaneously.

 

12kVA will only have a 60amp fuse and 16kVA 80amps. I would not think this is very future proof if you want to put in a 30amp supply to a car charger. I'd want at least 100amp fuse which is a single phase 20kVA supply in Ireland (It would be 23kVA but they round it I assume).

 

Moving to three phase will just allow you to have even more capacity if you need it, but other than the extra capacity I doubt any items you have will benefit from a three phase supply. Some items can use t but not many. They appear to offer a 29kVA single phase supply in Ireland. I guess that is a 120amp fuse.

 

 

 

[ProDave]

I would not be sure about the fuse rating.  We were only offered a 12KVA supply yet it has exactly the same 100A fuse as any other house in the street. The reason in our case was the number of houses sharing the same 100KVA transformer, and no doubt if we had asked for more, there would have been a capital cost to upgrade that transformer.