Domestic 3-phase to 1-phase

[user1842]

Hi,

I recently purchased an old house and it has a 3-phase supply (it is a semi-d, 90m2, with a overhead supply). It needs to be fully re-wired. My electrician notes that there is no need to use the 3-phases and recommended to just use one of the phases (and neutral) connected to a standard single phase consumer unit. Basically to then run the house from just that phase (which would include a 8kW heat pump).

The electrician noted this approach would be a lot simpler and cost a lot less (we are under significant budget pressure).

I don't see any major issue with this approach, would unbalanced loads be really an issue here?

Thanks

 

[JohnW2]

Hi,

I recently purchased an old house and it has a 3-phase supply (it is a semi-d, 90m2, with a overhead supply). It needs to be fully re-wired. My electrician notes that there is no need to use the 3-phases and recommended to just use one of the phases (and neutral) connected to a standard single phase consumer unit. Basically to then run the house from just that phase (which would include a 8kW heat pump). .... The electrician noted this approach would be a lot simpler and cost a lot less (we are under significant budget pressure). ... I don't see any major issue with this approach, would unbalanced loads be really an issue here?

I see no problem with that. Let's face it when (as usual)one just has a single-phase supply, it's just one of the three phases which 'runs down the street'.

Have you any thoughts of EV charging? If so,a 3-phase supply could be advantageous - but you could still run everything else in your house off just one of the phases.

Kind Regards, John

 

[ericmark]

To have the phases removed often costs, and once wired as single hard to later split loads to use three phases for heat pump or EV charging, so I would wire as three phase even if running from one phase.

But I note not UK, so maybe better to ask some one in your own country as may be things we don't know about.

 

[JohnW2]

To have the phases removed often costs ....

I can't imagine why on earth anyone would want to have 'phases removed', and nor am I sure what a DNO would do if they were asked - just remove two of the fuses, perhaps?

, and once wired as single hard to later split loads to use three phases for heat pump or EV charging ...

I don't really understand that. As I said, thee OP can run everything else in his house from a single-phase CU using just one of the phases and if he subsequently wants 3-phase for,say, EV charging that can be arranged separately from the origin of the (3-phasee) installation.

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'!

, so I would wire as three phase even if running from one phase.

I'm not sure whether you're saying the same as me or something different! What do you mean by 'wire as three phase'??

 

[SUNRAY]

I can't imagine why on earth anyone would want to have 'phases removed', and nor am I sure what a DNO would do if they were asked - just remove two of the fuses, perhaps?

I don't really understand that. As I said, thee OP can run everything else in his house from a single-phase CU using just one of the phases and if he subsequently wants 3-phase for,say, EV charging that can be arranged separately from the origin of the (3-phasee) installation.

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'!

I completely agree. One local hall has a verified 3ph head and just a 1ph meter.
It's actually 2 self contained halls with 2 kitchen, 2 sets of toilets etc so 2nd hall has a 80A submain with a private meter.

Having done several plays there with the Drama group and struggling with minimal stage lighting supply and overall current levels with hand driers, electric cooking and some electric heating. I contacted DNO/energy supplier about changing meter to 3ph and installing isolator, advised it would be FOC subject to survey I asked administrators to arrange it, My plan being a phase for each hall and the 3rd a submain and private meterfor stage use (as the drama group were required to pay for energy useage when the stage was in use). During the next local church meeting they voted not to as they could see no advantage.

To have the phases removed often costs... so I would wire as three phase even if running from one phase...

I'm not sure whether you're saying the same as me or something different! What do you mean by 'wire as three phase'??

I suspect he meant to a 3ph isolator then just use 1ph of it as Eric does know.

 

[jurassic sparkk]

I can't imagine why on earth anyone would want to have 'phases removed',

Could be worth doing because if you don't need three phases you'll reduce your monthly standing charge.

 

[user1842]

Thanks all, indeed I will not be getting the 3-phase supply removed, just taking one phase and suppling that to a consumer unit.

The meter is in the garage so relatively easy to take 3-phases from it in the future for an EV charger while still keeping the single phase to the house.

The only issue I can think of is that should I be trying to balance the loads on the phases and to bring the 3-phases into the house into a 3-phase distribution board - a pricey option.

 

[Murdochcat]

Lots of homes around with 3 phase heads and only 1 phase being used.

Just ask the supplier to fit a single phase meter

 

[fixitflav]

The only issue I can think of is that should I be trying to balance the loads on the phases

Not with you. If you use just one phase the question of balancing doesn't arise, the way I see it. And if you ran another one or two 1-phase systems from the other phases, I don't think balancing would be your problem. More of an issue for the supply network over an area, and balancing won't be exact.

 

[JohnW2]

Could be worth doing because if you don't need three phases you'll reduce your monthly standing charge.

Not with any supplier I'm aware of. If you look at published tariffs, they merely state a daily Standing Charge without asking if one is talking about 1, 2 or 3 phases.

 

[JohnW2]

Not with you. If you use just one phase the question of balancing doesn't arise, the way I see it. And if you ran another one or two 1-phase systems from the other phases, I don't think balancing would be your problem. More of an issue for the supply network over an area, and balancing won't be exact.

Quite. As I wrote at the start ...

..... Let's face it when (as usual) one just has a single-phase supply, it's just one of the three phases which 'runs down the street'.

 

[SUNRAY]

Could be worth doing because if you don't need three phases you'll reduce your monthly standing charge.

I looked into this about 5 years ago and found no evidence of any variation between 1ph and 3ph costs.

 

[user1842]

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

Thanks again.

 

[JohnW2]

I looked into this about 5 years ago and found no evidence of any variation between 1ph and 3ph costs.

Indeed. As I wrote, I know of know supplier who charges differently for (usage of) single-phase and 3-phase supplies.

 

[JohnW2]

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

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 - since if you asked for it to be 'removed', it could then well cost you to have the other phases restored should the need ever arise in the future.

Kind Regards, John