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The main difference between the V2 and V3 (apart from the V2 being no longer available as a kit) is the V2 has 3 current inputs (but it's relatively easy to add another two using some prototype board externally), and the V3 has four current inputs. We believe the V3.4 is a little quieter electrically so the performance is maintained to slightly lower powers than with the V2.

If you wish to have accurate calculations for real power, you will need to measure the AC voltage on all three phases.  I can supply a PCB which operates in this way:

Details on my website's Shop page at http://mk2pvrouter.co.uk/13779.html

ok, so now I have my 3 x V3's can I just connect a CT to each one and I'm away or do I need to account for phase shift? I don't have ACAC adapters on phases 2 and 3 yet.

Thanks

Can you describe the set-up you're aiming for? What will your installation look like, where are you putting each emonTx and where are you measuring what?

I'm looking to buy PV + storage in a few years time and want to accurately calculate what we need. So I want to measure (over a 12 month period):

Kws used per day/week/year for power and heating

Peak load on each phase

I have 3 V3's & 3 CT's, each phase is read from inside the meter box.

V3-1 - Red Phase& Optical Meter Reader for Power

V3-2 - Yellow Phase & Optical Meter Reader for Heating

V3-3 - Blue Phase

Once we go PV, I'll use one to measure utility power and one for power.

TIA.

Thanks, I understand now. With what is essentially a separate installation for each phase, then you don't and can't account for the phase displacement between the phases. But of course you'll only be able to measure real power on phase 1 (the one with the ac adapter), and you'll need a 5 V dc supply for the emonTx's on phases 2 & 3.

But it looks as if the CTs are the secondary measurement anyway, because by definition the kWh optical input from your supplier's meter is correct (even if it's wrong!), and I assume you'll be using the CTs principally for measurement of the peak load current, and of course you'll get the load distribution across the phases as well. That could be important when it comes to in-feed tariffs and stuff like that, because you might find that you get charged for import on one phase even if you're nett exporting but most of the export is on the other two.

That's exactly it, thanks for the help.