3 phase distribution question

[Andy Unique]

Hi all,

I am in the process of doing some once-in-a-generation changes to a property and I've got something I'd like to achieve but I don't know if it's feasible.

The property is large and consists of two separate houses shared by members of the same family. There's also some fairly large outbuildings that are fed off of one of those properties in a way that was probably fine a generation ago but is a bit dodgy now. Both properties currently have overhead single phase supplies.

My ambitions are:

Part 1: I would like to pull the two single phase supplies out and replace them with a single underground 3 phase supply in to one of the outbuildings. I'd then like to run an underground supply to each of the two houses and also tap off power directly to run the outbuildings. I've spoken to the DNO and received a quote for this work (as far as the termination of the 3 phase in the outbuildings) and that's all fine.

Part 2: Ideally I would to preserve the ability to run 3 phase equipment in the outbuildings at a later date, and I'd also like to have the option to introduce solar and/or battery storage and have a single installation able to satisfy the whole site.

My electrician is saying that part 1 is fine but part 2 can't really be done at the same time. Is he right or is there anything he might not have thought of? Not that he's not good, but I think I'm asking for something a bit unusual here so thought it'd be worth asking.

Thanks

 

[JohnW2]

Part 2: Ideally I would to preserve the ability to run 3 phase equipment in the outbuildings at a later date, and I'd also like to have the option to introduce solar and/or battery storage and have a single installation able to satisfy the whole site.
My electrician is saying that part 1 is fine but part 2 can't really be done at the same time. Is he right ...

If I understand correctly, I don't really see the problem, at least with the abiklity tro run 3-phase equipment in the outbuildings, idf thety are going to have 3-phase supplies. As for solar etc., I suppose that depends on how it is done, but, again, I can't think what problem might be envisaged.

Are you sure that your electrician fully and correctly understands what you are proposing?

Kind Regards, John

 

[Andy Unique]

If I understand correctly, I don't really see the problem, at least with the abiklity tro run 3-phase equipment in the outbuildings, idf thety are going to have 3-phase supplies. As for solar etc., I suppose that depends on how it is done, but, again, I can't think what problem might be envisaged.

Are you sure that your electrician fully and correctly understands what you are proposing?

Kind Regards, John

Thankyou for the quick reply, John. No, it's possible he doesn't fully get it. We tend to have most our discussion verbally on the hoof and while I have no doubt about his practical skills this project is perhaps outside completely standard domestic stuff. Just to be clear, he is a fully qualified professional not a mate from the pub! And he's done a good job of various other projects over the years, so I do want to give him the work if I can.

I think this is what I'm after. Does the fact that the demand on each connection would be completely random make any difference? What sort of component would handle the distribution for this?

 

[Notch7]

maybe you need some redundancy in the cabling so the underground cables can be run now and whatever set up is decided later on there will be the cable options to do it

 

[JohnW2]

I think this is what I'm after.

I'm no authority, but it looks fine to me (and not dissimilar from what I have in my house). I would merely suggest that you probably should consdier running the EV charging from the 3-phase supply.

Does the fact that the demand on each connection would be completely random make any difference?

No. For what it's worth, the loads on the 3-phase supply to my house are very 'unbalanced' between phases.

What sort of component would handle the distribution for this?

You don't really need any ';component'. The three phases will come out separately from your 3-phase meter. You would simply have to have 'junction boxes' (e.g. 'Henley Blocks') on each phase, so that all three phases could also be distributed for use with 3-phase loads, as well as providing gthe single-phase supplies as you have indicated

Kind Regards, John

 

[Murdochcat]

I think you need an installation company who does PV & battery installations to advise you too.

Not all of us do this work on a daily basis either so choose your spark carefully. I suspect the PV / battery etc won't be cheap either - and sharing battery storage across separate homes won't be without some issues either.

 

[Andy Unique]

I'm no authority, but it looks fine to me (and not dissimilar from what I have in my house). I would merely suggest that you probably should consdier running the EV charging from the 3-phase supply.

No. For what it's worth, the loads on the 3-phase supply to my house are very 'unbalanced' between phases.

You don't really need any ';component'. The three phases will come out separately from your 3-phase meter. You would simply have to have 'junction boxes' (e.g. 'Henley Blocks') on each phase, so that all three phases could also be distributed for use with 3-phase loads, as well as providing gthe single-phase supplies as you have indicated

Kind Regards, John

That's so simple it hadn't even occurred to me that might be OK. So that sounds like this:

Given that my heat pump (etc) requirements are purely future planning at this stage, presumably all I really need to do is make sure there is an isolation switch so so that the electrician can work on this in future? This might even be standard practice now, I just know that when we moved in here I had to pay the DNO to come and install one before we could have our meter changed.

 

[Andy Unique]

I think you need an installation company who does PV & battery installations to advise you too.

Not all of us do this work on a daily basis either so choose your spark carefully. I suspect the PV / battery etc won't be cheap either - and sharing battery storage across separate homes won't be without some issues either.

Yeah, that's a good idea. TBH it probably doesn't make any difference at this stage (can't afford to do any of the fancy stuff yet) but I guess I'll know whether to plan around doing it in future.

Many thanks to all of you for the quick input.

 

[JohnW2]

That's so simple it hadn't even occurred to me that might be OK. So that sounds like this:

Yep, that looks alright to me and, as I said, essentially what I have in my (large) house. My only comment, as before, is that I think you might want go seriously consider running the EV charging from 3-phase.

Given that my heat pump (etc) requirements are purely future planning at this stage, presumably all I really need to do is make sure there is an isolation switch so so that the electrician can work on this in future?

Yep, again like mine. The first thing the electricity hits after leaving the 3-phase meter is a 3-phase (plus neutral) isolator - so the entire installation can be isolated for any work to be done.

Kind Regards, John

 

[Murdochcat]

What you also need to consider is the billing arrangements for the 3 properties. If you plan to feed power from the storage through to the other units the suppliers meters will clock this up as grid consumption and they will pay the supplier

 

[JohnW2]

What you also need to consider is the billing arrangements for the 3 properties. If you plan to feed power from the storage through to the other units the suppliers meters will clock this up as grid consumption and they will pay the supplier

That would be true if the single-phase supplies to the individual properties were separately metered but, as was implied by what UI wrote, given that they are all occupied by members of the same family, I was thinking in terms of a single 3-phase meter (hence single 'supply', as far as supplier was concerned, and hence a single bill) covering all of them) - in which case there would e no anomalies such as you mention, the only charge for 'grid consumption' being for electricity which was actually imported/used (by whoever) from the grid.

 

[Andy Unique]

That would be true if the single-phase supplies to the individual properties were separately metered but, as was implied by what UI wrote, given that they are all occupied by members of the same family, I was thinking in terms of a single 3-phase meter (hence single 'supply', as far as supplier was concerned, and hence a single bill) covering all of them) - in which case there would e no anomalies such as you mention, the only charge for 'grid consumption' being for electricity which was actually imported/used (by whoever) from the grid.

Yes, that’s the intention. The two houses are my parents and my family in a farm and barn and the arrangement is such that a chunk of what’s metered on one house is for the benefit of both anyway so they might as well be blended. I don’t foresee the two being sold separately for several decades.

 

[JohnW2]

Yes, that’s the intention. The two houses are my parents and my family in a farm and barn and the arrangement is such that a chunk of what’s metered on one house is for the benefit of both anyway so they might as well be blended. I don’t foresee the two being sold separately for several decades.

Thanks for clarifying - as you will realise, that's what I suspected. In that case, valid though it might have been had the properties been 'separately occupied' (i.e. 'by strangers', and separately metered/billed), I don't think Murdo's comment would be relevant to you.

I say 'might have been valid' since, had the properties been separately occupied/metered/billed (i.e. by 'strangers') I doubt whether you (or anyone) would have wanted to export any of your stored/solar/whatever electricity to the stranger's house

Kind Regards, John

 

[Murdochcat]

I added the comment so it’s considered at the beginning.

What ever you do it’s best to consider as many options as you can think of before you do anything and avoid being boxed into a corner

Out of interest how much have you been quoted for a new 3 phase supply?

 

[robinbanks]

I would merely suggest that you probably should consdier running the EV charging from the 3-phase supply.

Fairly unusual to have a 3 phase domestic AC charger, or even a 3 phase compatible car. Nearly unheard of to have a domestic DC charger..

Most people can get by with a 7kW just fine and would probably find two 7kW chargers for two cars more convenient (and probably cheaper) than one 22kW