3 Phase Connection

[Bonner]

Evening All, 

My first new topic so forgive me if it is the wrong section! I can see this has been discussed previously but I have a few specific questions ...

Been quoted a electrical connection at £2400 single phase and £2600 three phase. Thinking about future generation and car charging, is it worth £200 extra? Are there any other additional costs or other implications to having three phase supply? For example meter, consumer unit, cabling etc. Planning to connect into a kiosk at the plot boundary with temporary building supply taken off. Eventually, I would run three phase to the garage and single phase to the house (hopefully without bothering the DNO!). Appreciate any advice!

[Big Jimbo]

£200 quid. it's a no brainer.

[jfb]

Go for it.

[TonyT]

Definitely worth it.

if you can get PV you are laughing too!

[Dan F]

29 minutes ago, Bonner said:

Eventually, I would run three phase to the garage and single phase to the house (hopefully without bothering the DNO!). Appreciate any advice!

This is exactly what we are doing.  3-phase in garage for PV and future car charging, but keep house on single-phase.

 

Keeping house on single-phase is simpler IMO, and means that if you install something like a Powerwall, you can backup house with 1 battery and don't need 3.

 

3-phase for PV means it's much easier to get a decent size array approved by DNO.

 

No down-side with having 3-phases, you can just use one of them if you like.   Until recently we only have a single-phase meter connected to one of the supply phases.

Edited November 11, 2020 by Dan F

[Bonner]

42 minutes ago, Dan F said:

No down-side with having 3-phases, you can just use one of them if you like.   Until recently we only have a single-phase meter connected to one of the supply phases.

Hadn’t thought of that! Not sure if the DNO will entertain that assuming that they need to fit the meter? Would the spare phases just be terminated in a box before the meter?

[Big Jimbo]

I've got three phase. Only One is connected to the meter. The other Two are just terminated in the box.

[joth]

11 hours ago, Bonner said:

Hadn’t thought of that! Not sure if the DNO will entertain that assuming that they need to fit the meter? Would the spare phases just be terminated in a box before the meter?

DNO doesn't have anything to do with the meters, they just provide the cutout and 100A fuses and everything downstream of that is up to your supplier(s). When I talked to our dno about this they said it's very common in London for larger houses to be split to flats and the phases then gets assigned to a different flat, with each occupier getting their own choice of supplier on that phase (or 1 phase  unused if there's only 2 flats, say)

Edited November 12, 2020 by joth

[Innes-]

On 11/11/2020 at 20:04, Dan F said:

Eventually, I would run three phase to the garage and single phase to the house (hopefully without bothering the DNO!). Appreciate any advice!

Hi, I like this idea and have been exploring something similar myself recently. I'm wondering what metering would look like in practice? Is it possible to have a 3 phase meter installed but only take one phase in to the house and 3 to the garage?  Alternatively if there was a single phase meter on the house supply would there need to be an independent 3 phase meter in the garage?  

[joth]

1 hour ago, Innes- said:

Is it possible to have a 3 phase meter installed but only take one phase in to the house and 3 to the garage? 

Yes

[Innes-]

44 minutes ago, joth said:

Yes

Thanks. If a large (12-18kw) solar array was installed on the 3 phase supply in the garage would the house need to be 3 phase as well to make full use of the electricity that was generated? 

 

 

[pdf27]

1 hour ago, Innes- said:

Thanks. If a large (12-18kw) solar array was installed on the 3 phase supply in the garage would the house need to be 3 phase as well to make full use of the electricity that was generated? 

Shouldn't do - the meters sum across the three phases and are supposed to be able to cope with export on some phases and import on others. You're never going to perfectly balance across all three phases anyway.

[joth]

2 hours ago, pdf27 said:

Shouldn't do - the meters sum across the three phases and are supposed to be able to cope with export on some phases and import on others. You're never going to perfectly balance across all three phases anyway.

 

Yes, this is documented in the "SMETS2 polyphase" requirements, i.e. if you have a v2 smart meter it should work this way.

I understand commercial contracts maybe (very) different on this, with a requirement to balance phases and stuff, but in general domestic customers shouldn't be penalized for microgeneration with imperfect load balancing. But if you don't have a smart meter (or, maybe even if you do) there seems to be a very real risk the supplier will configure the meter incorrectly and bill on some other basis. 

 

[Jilly]

Bargain. Mine was £8700 ?

[Bonner]

Update - the first quote was an estimate, apparently not taking into account there is no 3 phase supply nearby!!

The area engineer rang me last week to ask if I really need 3 phase because they would need to extend their network which would cost (me) ‘5 figures’. So I won’t be having 3 phase then ?

[Dan F]

5 hours ago, Innes- said:

Thanks. If a large (12-18kw) solar array was installed on the 3 phase supply in the garage would the house need to be 3 phase as well to make full use of the electricity that was generated? 

 

We'll have:

- 3-phase supply to garage,

- 12kW 3-phase PV inverter in garage (16kW array)

- Duct through slab that takes 1 of the phase to a consumer unit in plant room (inside thermal envelope) that serves the house.

 

(garage distribution board will also serve garden, and front gate etc.)

[MrTrevithick]

On 07/12/2020 at 17:55, Bonner said:

Update - the first quote was an estimate, apparently not taking into account there is no 3 phase supply nearby!!

The area engineer rang me last week to ask if I really need 3 phase because they would need to extend their network which would cost (me) ‘5 figures’. So I won’t be having 3 phase then ?

Shame, a very useful little bonus to have especially if you ever set up a workshop because secondhand 3 phase kit is not only better it is cheaper as well. For my 3 phase I have a rather nice but bloody heavy old generator.