3 Phase Solar in but single phase ASHP?

[MMcGill]

Hey all - my ASHP supplier has installed a single phase ASHP rather than the three phase I ordered and is trying to convince me it won't matter - The house has three phases available. Now I get that the electrician can balance across the phases so from a supply no problem, but I also have a 13kwh of solar with a three phase inverter, his view is again no problem as the conumer unit will put power to whatever phase is calling for it... Is this right, I',m not in the detail of this one and worried that the ASHP will only be able to make use of one phase worth of solar? Any pointers to reading material / your views would be helpful!

 

[Andehh]

Watching this thread with interest. We had 3 ph installed and our electrician sort of explained it as an everything comes in, mixes together and feeds everything out.... But then our electrician was a (expletive deleted)ing moron on anything other then the basics, so I don't know what he did behind the 3ph consumer unit.

 

It all works, but when 22kw car chargers and 3ph solar get installed in years to come who knows what headaches I'm in store for.....

 

 

[LiamJones]

Phases won’t mix, they’ll all come in/go out individually through your supply head from the DNO. You’ll need a 3 phase meter with vector sum metering, that’ll add up all phases and work out whether you are importing or exporting over all to avoid exporting on 1 phase then paying (more) to import on the others.

[markharro]

1 hour ago, LiamJones said:

You’ll need a 3 phase meter with vector sum metering

Im in a similar position and remember checking with Octopus that their meter does this and they said yes. We have 3phase into the house with an ASHP to be installed and 6kw of solar but with the potential to expand to 11kw. We have a 3 phase inverter I think. We are getting a Zappi with the higher 22kw charge rate but I am a bit clueless about the Viallant heat pump. Is there such a thing as a 3phase ASHP and should I be specifying thats what I need? If so why?

[LiamJones]

Unless you need a large heat pump (lots of kWh) no, I don’t think there’s any benefit. Just stick it on its own phase.

[Andehh]

FWIW we have a 1ph 12kw unit, never occurred to me to get a 3ph...

[freshy]

1 hour ago, LiamJones said:

Unless you need a large heat pump (lots of kWh) no, I don’t think there’s any benefit. Just stick it on its own phase.

How big is a large heat pump?

 

Watching this thread with interest since I have a 3-phase supply and the solar installer is telling me I don't need a 3-phase inverter for my 6kw solar PV. 😕

[MMcGill]

14kwh heat pump for me - 13.6kwh solar over three phases…

 

bit I’m still trying to figure is;

 

if solar is outputting 12 kWh and the three phases are drawing;

 

1 - 8kwh (where the heat pump is)

2 - 2 kWh 

3 - 0 kwh

 

I would hope that we’d us 10 of the 12kwh available, however, this is the bit i don’t know, if the solar is on the phases evenly ie 4kwh each will I instead have to rely on the meter to recognise the balance of incoming and export;

 

so using the above;

 

1 - Using full 4 in but draws 4 from the grid

2 - Uses 2 exports 2

3 - exports 4

 

so the meter recognises the above so nets it to 2kwh export.

 

or is there something in between to ensure the full 12 of solar is used before pulling anything from the grid?

 

[Alan Ambrose]

>>> the conumer unit will put power to whatever phase is calling for it...

 

Hmmm, nonsense - in the sense that it can’t move power from one phase to another. So, that could leave you exporting on 2 phases while you import on the phase the HP is connected too. Which may have a cost penalty unless your supplier does the net-metering thing.

 

ideally you use all PV power you generate on site first *before* sending some back to the grid. This added complexity of phase balancing and contractors being less familiar with 3P inverters, HPs, car chargers etc is one of the downsides of 3P.

[joth]

Search this forum for "polyphase" it's been covered many times. So long as you have a SMETS v2 smart meter vector sum metering is guaranteed by the standard.

If you have an old installation with separate import and export meters, good luck: the suppliers often don't know how it should be setup, and the installation contractors often fail to set it up properly even if told. 

 

https://forum.buildhub.org.uk/search/?&q=polyphase&search_and_or=and

 

Edited November 17, 2023 by joth

[MMcGill]

Thanks - new build so new Octopus meter so fine from that perspective 

[Alan Ambrose]

>>> vector sum metering is guaranteed by the standard

 

Ah, so in a sense, his HP man is 'right' - that is the DNO will 'exchange' your export for import at zero price difference.

 

[Carrerahill]

On 16/11/2023 at 16:53, MMcGill said:

Hey all - my ASHP supplier has installed a single phase ASHP rather than the three phase I ordered and is trying to convince me it won't matter - The house has three phases available. Now I get that the electrician can balance across the phases so from a supply no problem, but I also have a 13kwh of solar with a three phase inverter, his view is again no problem as the conumer unit will put power to whatever phase is calling for it... Is this right, I',m not in the detail of this one and worried that the ASHP will only be able to make use of one phase worth of solar? Any pointers to reading material / your views would be helpful!

 

Simply, it is not ideal.

 

The issue you have is your ASHP will pull from say L1, however your PV will generate on L1/L2/L3 - any benefit of self consumption of L2/L3 generated power will be lost where house load is low as you will push that to grid, i.e. export getting pathetic SEG payment rather than benefit of use which, financially, far outweighs SEG payment. 

 

Also, phase balancing is all very well in theory, in that your electrician may load L2 and L3 with more house load than L1, in practise if your house loads are low, all electric loads more or less off and ASHP going full pelt you now have a nice imbalance, not really your issue, more the DNO/local transformer, but not ideal - can cause neutral issues. 

 

 

Edited November 17, 2023 by Carrerahill

[joth]

5 minutes ago, Carrerahill said:

The issue you have is your ASHP will pull from say L1, however your PV will generate on L1/L2/L3 - any benefit of self consumption of L2/L3 generated power will be lost where house load is low as you will push that to grid, i.e. export getting pathetic SEG payment rather than benefit of use which, financially, far outweighs SEG payment. 

 

This is incorrect. I can point you at the smart meter spec that makes vector summing clear, if it helps.