1 or 3 phase wires on the poles?

[pdf27]

My electricity supply comes in via an overhead wire, with the pole in verge in front of the house next door where it goes underground for the final few meters. Is there any way of telling whether the overhead wires themselves are 3 phase or single phase without asking the DNO?

I've been mocking up the house we want and working out how big a PV array I could potentially fit, and how cheap it would be (Midsummer are quoting £4200 for the bits for a 10kw in-roof system), and am suddenly coveting a 3-phase connection. Since I'd have to move the connection anyway (it comes up through the current floor slab), I'm suddenly very curious.

[ProDave]

Post a picture here for us to scrutinise.

 

I assume this is an LV line (230V) and you come directly from that? or is it an HV line with a transformer up the pole?

[pdf27]

LV line running down the street providing power to the ~120 or so houses on the street.

I'll take some photos tomorrow morning when there's a bit more light.

[Nickfromwales]

10 minutes ago, pdf27 said:

LV line running down the street providing power to the ~120 or so houses on the street.

I'll take some photos tomorrow morning when there's a bit more light.

Count the number of wires that form the twisted trunk, or are these a run of single strands off a pole?

 

This is 3-phase

 

or twisted?

This could be 2 or 3 phase so more difficult to tell.

[pdf27]

I **think** it's twisted (will take a detailed look tomorrow), but I don't know if they wrap single phase (L+N) around a steel supporting wire at all. Helpfully the pole only says "this is an electricity pole"! There is certainly only one wire or bundle of wires on it.

[pdf27]

Street view image of the pole in question...

 

[Nickfromwales]

That's 3 phase I'm pretty sure. You can see 4 connectors L1 L2 L3 and neutral.

FYI you could also ask the DNO to fit 8kWp and employ export limitation down to 3.9kW if 3-phase isn't a goer.

 

I assume you'll get a 3-phase inverter if you go 3-phase supply? Fronius are very good.

Edited July 31, 2020 by Nickfromwales

[pdf27]

Likely to be a year or two, but it's hard not to see 3 phase making sense given it's all of 4m from the edge of my driveway. 3 phase inverter would pay for itself in no time - Sunny Design reckons it would be a couple of MWh extra exported per year without the 3.9kW limit, and the export limiting kit is something else to wire up and go wrong. There really isn't a lot of price difference between inverter brands, so it makes sense to get a decent one.

 

The other side of things is that we're definitely going to be a 2-car family for a long time to come, and that means we'll have 2 electric cars to charge. 3-phase gives us one phase for each car and another for the house, which should help a lot when time-of-use tariffs become much more common in future.

 

Edit: pink garage on the right is where my electricity meter is at the moment.

Edited July 31, 2020 by pdf27

[Nickfromwales]

5 minutes ago, pdf27 said:

pink garage on the right

"it's not pink, it's salmon!"   

Agree on the export limitation being a negative, but FYI it's inbuilt into SolarEdge inverters IIRC and they have dry capacitors and a 12 year warranty.

Edited July 31, 2020 by Nickfromwales

[ProDave]

I agree that looks like 3 phase. I wish I could remember the name for those twisted cables.  As there are only 4 connections, not 5, it must be PME earth, which is unusual for overhead, but we had that in a previous house.

 

Which house are you knocking down?  the one in the picture looks too good?

[dpmiller]

ABC cable Dave I think, Aerial Bundled Cable.

[pdf27]

5 hours ago, ProDave said:

I agree that looks like 3 phase. I wish I could remember the name for those twisted cables.  As there are only 4 connections, not 5, it must be PME earth, which is unusual for overhead, but we had that in a previous house.

 

Which house are you knocking down?  the one in the picture looks too good?

The one in the picture is the neighbours - it's a 15 year old Potton kit. We're hoping to do this one, budget permitting:

Fairly small house, huge plot (1/4 acre) right on the edge of the London green belt, awful 1970s extension on the back and pretty much everything inside (kitchen, bathroom, plumbing, heating, etc.) is a bit elderly and needing work. Could easily spend £50k just getting everything working properly!

The original plan was to refurbish and extend upwards, but we had to drop that when the prices came back as more than new build, and at the time we didn't have the budget to rebuild. We may have had a lucky escape on that - a very similar house across the road had to be demolished and rebuild when they tried to do it and found it essentially didn't have any foundations - bit of a problem on clay with a high water table!

I **think** we probably have the budget to do this now, but having been quite badly burned last time I'm planning everything I want to do (up to and including designing/specifying what I want to do) and costing it out before we start getting professionals involved and actually spending money on it.

Edited August 1, 2020 by pdf27

[Randomusername]

I’m toying with the idea of three phase for my rural 2 x new build project, what with the potential demands of heat pumps, solar PV, car charging in the near future. 
Similar to you - As I’ve got the main supply transformer sat on poles in the verge outside the plot it seems to make more sense as the cost of connection must surely be significantly reduced by the proximitity of the supply? As long as there is sufficient capacity and they don’t want me to start paying to upgrade their network... something to bear in mind.