Addding 3 phase inverter to IoTaWatt setup

Hi Everyone,

I Have an IoTaWatt installed which is monitoring the consumption on 12 circuits in my home and I looking at getting solar installed at my place. It looks like the inverter will be 3 phase so I assume there will be 3 phases that will need to be monitored by the IoTaWatt.

My IoTaWatt has 2 unused inputs (13 and 14), will it be possible to use the IoTaWatt to monitor a 3 phase inverter with only 2 CTs?

If the inverter distributes production evenly across each phase can I get away with monitoring a single phase and multiplying by 3 (or the sum 2 phases and multiplying by 1.5)?

Can I run all 3 phases through a single CT and get production for all 3 phases on the one CT?

here is a snapshot of the current circuits on my IoTaWatt.:

I can rearrange some circuits on the board but I want to have a plan so the I know what should be done so it can all be sorted by the spakie on the day the inverter is installed.



Maybe. If the inverter connects with 3 wires and does not use a neutral.

Yes you can if they are equal or nearly so, but that’s a big IF. You can measure them with IoTaWatt to find out but then it’s kind of a catch-22.

No, all of the circuits on a particular CT must use the same reference phase/voltage. The status display doesn’t show the phase of each circuit, so I can’t say what could be combined. Would need to see the inputs display with the phase assignments.

There are other ways to combine circuits. You can use a headphone splitter to combine two or more CTs into one input:

  • They must be the same model/capacity.
  • The total Amps of all must not exceed the capacity of the CT model.
  • The circuits must have the same phase reference.

Thanks @overeasy,

it looks like the inverter includes a neutral line:
“Grids Supported - Three Phase: 3 / N / PE (WYE with Neutral)”

as for the balanced loads from the inverter - as you say catch-22 I will probably need to shift some circuits around to free up a CT (or as you suggest consolidate 2 CTs with a 3.5mm splitter).



What model inverter ? 99% of them that i have come across (In Australia) - all balance the output across all 3 phases - so measuring one and tripling it would be pretty close - the issue is that the usually balance the amps output on each phase - so if there is a big difference in voltage between your phases your results will be skewed


Thanks @craigcurtin that makes sense, the inverter am looking at is the SolarEdge SE7k-AUB hybrid inverter.

I guess I could put the 2 spare CTs on 2 phases and sum them and multiply by 1.5 and get a more accurate reading.

Yep if its AU it will try to balance all 3 phases (which is prety stupid if you think about it - would make much more sense to feed more current to the lower voltage phases to enable them to be raised) - but that s how inverters are made - have not seen one you can do differently

You are not talking a lot of difference really - between my 3 phases i have a 5 volt difference from highest to lowest.



Thanks, Craig,

That makes it easier to monitor, however, as you say - it would be more sensible to feed into the lower voltage phase as needed.

Much appreciated.