Australian Split Phase

Hi everyone

I am in a country area in Australia and we use a split phase 240 Volt system. IE: two phases being delivered to the house but 180 out of phase and 480Volt across the two.

Should I configure two VTs onto one Iotawatt or do I have to use two units and treat them as two isolated single phase 240 Volt systems?

Does the system support split phase 480 or perhaps I configure it as a 3 phase with one phase missing?

Any guidance would be appreciated.


There are a couple of ways to approach this. First impression is that it’s not unlike a North American 120/240 split phase system, but maybe there are some differences. In North America, the single phase is split with a center tapped transformer. I’m assuming that’s what’s going on here, and if so, I think you would be fine with a single 230/240 Volt VT.

If, for some reason, the two phases come from different transformers, you may need to use two VT’s, but that is easily handled by IoTaWatt. I would recommend you wait about a month for the version 5.0 IoTaWatt that will have native ability to support up to three VTs.

You should not need two units unless you need to monitor more than 14 circuits.

It would be a single transformer. No electricity network company would (should) feed a single premise with phases from two separate transformers.

The Australian system is 3 phase 90˚ out of phase with a cross-phase voltage of 415 not 480. Some houses get 2 phases delivered although it’s pretty rare. Here’s a graph of the voltage variance between phases at my house (in 2046) over a 40 minute window or so. They seem to track fairly well and I’d say that it’d be reasonable to get your voltage from the 9V AC input on the device on one phase and multiply each of your phases current readings by that voltage. You will however lose pf measurements I’d imagine which will mean you won’t be measuring real power, rather apparent power.


That would work for apparent power, but to measure real power it’s necessary to have a voltage waveform in phase with the current. IoTaWatt can do this by numerically phase shifting a reference phase (derived reference) or by using discrete VTs for each phase (direct reference). The advantage of direct refer3nce is that it picks up any variation in voltage. Most IoTaWatt users have one VT and get reasonably accurate results with derived reference.

Pretty sure the phase to phase angle is 120° for three phase electrical power everywhere in the world. The voltage does vary and it can be in a Delta (3 wire + ground) or Y (3 phase wires + neutral + ground) configuration.

Split-phase in the US is 180° apart by grounding the center tap of a transformer that is connected to a single phase of the (3 phase) high voltage distribution line.

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It would be 120 degrees. In Australia it would be in almost all cases 3 phase and neutral (star winding on output of transformer) provided for a 3 phase connection. The earth wire (ground) would be created at the meter board with earth stake and bond between neutral and earth.

A single phase connection is a single phase conductor and a neutral.

There are some less common supply arrangements, for example a SWER transformers as well…

Late nights and cloudy heads - it’s definitely 120˚- apologies

Hi I am a newbie to this group and not super techie. Many country properties get two phases (mine is 32amps each phase). Apparently it is used to balance loads or such in single run lines where we have many houses on a dead end road and one line. I am looking at the Aussie bundle and wondering if I need two units or can go with one?

Almost certainly one IoTaWatt, but the rest is unclear. Are you saying you have two 230V mains and a neutral?

It’s a holiday week end here and it’s late, so responses tomorrow will be slow.

Yes two 240v phases each 32amp and a neutral.

You can use one V5 IoTaWatt. If your mains cables are less than 10mm, you can use ECS1050 CTs, otherwise you will need 2 ECS16100 for the mains. Order up to 11 more ECS1050 for individual branch circuits.

You will need one AC transformer for derived reference, or two for direct reference. I recommend you buy the AC reference transfomer(s) and USB power supply locally from Radio Parts as in the description at the bottom of the Aussie bundle.

I also live on a 2 phase (180 degree) rural service. The Transformer CT is Neutral (& MEN Earthed), so the 2 phases are opposite. I had an argument with Essential Energy when my 2 of 5Kw inverters were commissioned, in that he said all current (ie 10Kw) flowed back on the Neutral (which is incorrect) so limited me to 8.4 kw export.
I have just ordered an IoTaWatt for my installation. I have 2 of SolarEdge 5kw inverters, as well as a Victron charger/inverter on one phase connected to 4x 2Kw Zenaji batteries (Lithium Titanate packs made in Australia).
My feeling on the Voltage reference is if the phases are reasonably matched, one reference should be enough, but in my case I intend to have both phases referenced.
btw, I have a wired ethernet connection to my Inverters & CCGX. I will interface the IoTaWatt with a simple router: cheap & easy! I get 4 ports for the existing inputs & the Wan port to the other router. Wifi for the IoTaWatt. All for $29 fo a TL-WR841N.
Too easy!
(Doug in N NSW, Australia)
Anyway, more on my system later

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Hi Doug

I also live on a two-phase polyphase 180 degree 480Vac home.

Keen to know how you went with the IoTaWatt. I also have a solar system split over two-phases.

By the way the neutral is common to both phases.

Peter (Far North Qld(

That’s an old post so I don’t know when @Doug will see it. My take on this is that it’s probably the same as North American split-phase except 240V/480V instead of 120V/240V. It would make no sense to distribute two phase 180° apart when you can just pull both from a center tapped transformer. It also offers no advantage in motor starting like three-phase. IoTaWatt should work fine with one 240V transformer.

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I have asked a similar question in my latest post. With a few more technical questions.