3 Phase AC monitoring

Hey Everyone,

I am in Australia and looking to purchase an IoTaWatt. I am just planning out what i need and I would like to confirm with somewhere here before I make the purchase. I have three phase power and we have ducted inverted AC. It looks like the external AC unit is three phase (I am not sure as I am a bit of a noob at all this) with an additional circuit for the internal unit. Do I need to put a CT on each wire of the external AC unit to monitor its power usage? Or will a single CT be sufficient?

Below is a picture of my breakout board.
I am looking at purchasing the following - please let me know this is correct for my needs.

  • 1 x IoTaWatt v5
  • 3 x 100A CTs for Mains
  • 9 x 50A CTs (4 x AC, 1 x Solar Inverter, 1 x Kitchen Power, 3 x Power)

Any advice would be much appreciated.

That should work. Couple of things:

That depends on whether the unit loads each phase equally and how precise you want to be. You will have plenty of CTs at your disposal, so what I would recommend is that you start out doing all three, and then after a day of use, plot the power for the three and see if they are more-or-less the same. If that’s the case, you can remove two and define an output that is the remaining leg x 3.

I see that you are ordering 12 CTs. I will assume that is because you intend to use three VTs. Since you acquire them locally, you might want to try out using derived reference with just one VT to see if the results are satisfactory. That is by far the most popular approach.

I don’t see a breaker labelled as PV or Solar Inverter. Is that elsewhere? Is the inverter single or three phase?

Regardless, the above order should be fine with the caveat that if you are not going to use 3 VTs, there is room for two more CTs, and you can add them at discount and minimal impact on shipping now.

Thank you so much for the reply.

I think I will monitor all three phases. I live rural and its difficult to get an electrician out here so, where possible I want to do it once and right.

I’ve just checked the solar inverter and it looks like It is 1 phase, 2 wire. Below is a picture of the whole box. There are two switches for Solar Supply Main Switch. - Do I need to monitor both wires in this instance?

I should have mentioned in my original post I intend to only use one VT and use derived reference.

Thanks again for the assistance!

Your solar looks to be only single phase so only need 1 CT on the active conductor. The switch is a double pole switch and interrupts both the active and neutral conductors simultaneously.

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