Domestic 3-phase to 1-phase

[SUNRAY]

Excellent, thanks all. One phase to the house it is then. I will let the electrician know.

Thanks again.

Yes - but as I said, I would fairly strongly suggest that, although you will only use one of the phases for your your house, that you nevertheless retain the 3-phase supply...

Kind Regards, John

That is how I read 1842's comment.

 

[user1842]

100% keeping the 3-phase. The existing 3-phase day/night meter will not be touched

 

[JohnW2]

That is how I read 1842's comment.

Well, I hoped that's what he meant (which he has now confirmed) but "one phase to the house" was a bit potentially ambiguous.

 

[Why Not Indeed]

He said his meter's in the garage. One phase to the house really only has one meaning here.

 

[JohnW2]

He said his meter's in the garage. One phase to the house really only has one meaning here.

I'm not sure why we are discussing this given that the OP has now confirmed what he meant, but ....

... yes, "one phase to the house" means "one phase to the house", with no other possible meaning I can think of. However, I did not feel that those words confirmed with certainty that the OP was going to retain all three phases at the garage (as I had suggested/advised), which is why I asked him to confirm (which he did).

 

[ajohn]

Given that (at least in the UK) it costs nothing to retain a 3-phase supply, I think it would be daft (in terms of 'future proofing) to ask for two of the phases to be 'removed' even if one was only going to be using one phase for the foreseeable future (and no-one will ever know that,since a 3-phase meter merely gives a total across all phases) Getting the two ('removed') phases back should a need arise in thee future could well 'cost'!

Me neither and I wonder about cost. If cabling needs to be run or replaced it will be either way. It might be done with 3 small CU's or I assume a 3 phase CU. That would be the additional cost.

I live in a 1911 house that was wired with 2 phases. Thanks to smart meters and lack of answers it now uses one. The street wiring of a house that old is not up to modern standard. 2 actually isn't a bad match. Why 2. That was down to 2 people owning the house but not in a flat sense who wanted separate bills. 2 kitchens etc. Can't say I am happy about just one but didn't want to pay 2 service side charges The set up used 2 small CU's. Now fuse removed from one phase and jumper cables.

It did have 2 gas meters as well. An easier aspect to fix.

 

[JohnW2]

Me neither and I wonder about cost. If cabling needs to be run or replaced it will be either way. It might be done with 3 small CU's or I assume a 3 phase CU. That would be the additional cost.

Yes, but we are all agreed that the OP only needs one (single phase) CU,and that remains the case if three phases are entering his property and, at least for the foreseeable future, he only uses one of them.

 

[ajohn]

I wondered about each phases load capacity and also what they want to load it with. In part due to people having a higher rated fuse fitted and finding they need 3 phase as load regs aren't met. Something I have seen mention of happening. Exteme load true but it happens. In this case if this does happen fine as the phases are there.

My house - what was the original supply fuse rating? Given the time it was built and installed it might even be less than 60. There are still a couple of old style unconnected sockets around. I don't know when there has been rating changes. New installs as far as I am aware are always true 100amp.

 

[JohnW2]

I wondered about each phases load capacity and also what they want to load it with. In part due to people having a higher rated fuse fitted and finding they need 3 phase as load regs aren't met.

Most domestic properties are fed with just of one of the three phases 'which goes down the street' and the cabling and total local network capacity is commonly such that the supply (of one of the phases) to each supplied property can support a supply of up to 100A. It is when demand rises to above 100A (e.g. because of EV charging/heat pumps/showers) that it may be necessary to move to 3-phase.

My house - what was the original supply fuse rating? Given the time it was built and installed it might even be less than 60.

It might have been. These days, 3-phase supplies to sinle domestic/residential properties commonly have 60A fuses, and it's likely that such a property would require more than 180A total (if they were using all three phases.

 

[bernardgreen]

In Germany 1972 three phase supplies to domestic properties were not uncommon. Mainly for supplying three phase electric showers and storage heaters.

They are available in the UK

One of many suppliers is
https://www.aquahot.co.uk/water-hea...s-electric-water-heaters/three-phase-electric

 

[JohnW2]

In Germany 1972 three phase supplies to domestic properties were not uncommon. Mainly for supplying three phase electric showers and storage heaters. ... They are available in the UK

Maybe, and there ae also some large cookers (and probably other 'large' items) in the UK that can be fed with 3-phase (usually as 'an option').

However, I think it's probably fair to say that, although quite a few UK domestic properties (like mine) have 3-phase supplies, if more than one phase is used, the phases are usually used 'separately, as /single-phase' (again, as in my house), and it is pretty rare to see any '3-phase wiring' or 3-phase loads in domestic UK premises.

 

[Ragnar_AT]

Continental 3-phase fuse boards are cheaper and more compact than their UK counterpart, which are mostly designed for industrial use. In fact, the only differences are the RCDs and bus bars, the enclosure is exactly the same for single and three phase. Therefore, installing three-phase CUs comes at hardly any extra cost. Five-core cable is used all over the place and easy to get. Given that, it’s easier to run five-core 2.5 to a cooker than 6 mm2 three-core. Instant water heaters in Germany usually supply the whole bathroom and are 18, 21 or 24 kW, which would be a massive load on a single-phase supply.

 

[plugwash]

Yeah, as you say three phase busbar sets for regular CUs don't seem to be a thing in the UK. Three phase distribution boards in the UK designed for circuits of 63A or less* always seem to use a large central "PAN assemly" with the main switch mounted below and the MCBs mounted horizontally down the sides.

I wonder if there is a regulatory reason for this, or if it's just a case of "we sell what we have always sold".

It's not just industrial use, while TP boards are rare in domestic properties, commercial properties are full of the things.

* Boards intended for higher current circuits use a similar overall layout but with MCCBs instead of MCBs.

 

[robinbanks]

Just make sure you're comparing apples with apples when talking about "an 8kW heat pump" - if 8kW is it's heat output then it's electrical input will likely be a third of that or less; less than a fast kettle.

Even if the electrical input is 8kW (which would make it's heat output around 24kW, which is fairly monstrous in HP terms), it'll still run easily off a single phase setup, using commonly available cable diameters - you can buy electric showers that are more demanding

3 phases would give you a 22kW EV charger, but this isn't the full story; very few cars on the road will accept a full 22kW AC. If you bought a DC charger you might well get 22kW charging, but the prices of DC chargers are insane..

Suppose you had sn EV that did accept 22kW, and also had an 88kWh (an uncommonly large battery size for an EV) battery - it would notionally charge from 0 to full in 4 hours (actually a little longer, as they slow down as they become full).. be really honest with yourself re your driving habits though - do you really drive so much that you could only spare 5 hours to fill your Jaguar I-Pace every dsy? (note; an ipace doesn't accept 22kW, a Renault Zoe will and with a 50kWh battery is 2-3 hours charge but again, do you really need the speed?)

Mostly when people set out on the eV ownership journey they frame it in terms of what they know about fossil cars; fill ups are a 10 minute process at Asda on the way home and the lead assumption is they have to have a way of recharging their EV quickly. Mostly it's nonsense; perhaps valid for taxis driven by two drivers on shift, but regular people leave their car stationary outside their house for far longer than they drive it and as such even a lowly 3kW granny charger can suffice for a considerable cross section of users, let alone a 7kW single phase AC wall box

 

[JohnW2]

Yeah, as you say three phase busbar sets for regular CUs don't seem to be a thing in the UK. Three phase distribution boards in the UK designed for circuits of 63A or less* always seem to use a large central "PAN assemly" with the main switch mounted below and the MCBs mounted horizontally down the sides. .... I wonder if there is a regulatory reason for this, or if it's just a case of "we sell what we have always sold".

The 'why' (in the UK) question is an interesting one - and your suggested answer may well be correct.

However, I doubt that the reason is 'regulatory', since single-phase-like ones are offered for sale in UK For example ...
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