New Aussie 3 Phase Install - Some follow up questions

Hi all

I just installed my IotaWatt, not real issues with installing it and loving the information its giving me already. Its a temporary install at the moment and was wondering the best way forward to configure my setup.

I have 3 phase power, with 3 phase solar and AC. I also have 11 separate circuits.

At the moment I am not monitoring the mains or solar. I have a power meter with my inverter which is doing that. So my 14 inputs are 3 phase ac + 11 circuits using derived reference.

Its a temporary install because at the moment I have an extension lead from the garage to a powerboard (in a weatherproof box) by the switchboard. The power then goes into a plastic box which houses the IotaWatt and I have 25mm conduit from the switchboard into the same box for all the CT.

I am getting an electrician in to install some new sockets soon either inside or near the switchboard.

Firstly, should I consider getting multiple sockets, one (or double I guess) for each phase. I could then switch over to direct reference. I am wondering how much more accurate it could be with direct vs derived… at the moment the total it seems to be within 100w of what my inverter is reporting, but my phases are within 3v of each other, and I’ve seen them out differing by 10-15v sometimes during the day, who knows if it goes higher. I can afford to combine some circuits to free up inputs. There are 3 lighting circuits, but the entire house was halogen at one point and now its LED… so with everything on its only using 600w (5kw with bathroom heat lamps but they never get used)… so direct reference would be achievable if its worth doing.

Second, am I able to use my inverters power meter in any way to feed data to IotaWatt? If I could feed voltages from the 3 phases I wouldn’t need either reference maybe?. I could feed in main and solar usage… and later battery usage when we get that. I doubt I would never be able to monitor the battery as its a hybrid inverter and I would assume its DC from the inverter to the battery. But that information would change my readings a lot. IotaWatt wouldn’t know if the battery is charging, discharging… so solar would not be accurate at all. Multiple IotaWatt or data from external sources would make it a lot more powerful, and reduce the amount I need to monitor to get a full picture / use external sites. I can see myself getting a 2nd IotaWatt if I get an EV charger, and might end up monitoring everything anyway… but I would still need an external site to merge all the information from the 2 IotaWatts.

Hope that all made sense.


Capturing data and analysing it are two separate activities. Iotawatt does both but on limited circuits (more so with three phase as 3 inputs are needed to monitor each 3 phase ‘supply/circuit’).

Each iotawatt unit can only display the data it captures, it can’t add data from other sources - you will need something else to integrate and display data from more than one source (e.g. a second iotawatt or your solar). Most people with multiple iotawatt’s use influxdb to consolidate the information into a single database and then build dashboards in a graphing solution (I use grafana but there are others)

Unless there is massive variation in voltage on your phases then a single VT and derived three phase is your best option - you don’t need local sockets on each of the 3 phases and you don’t lose 2 inputs to the additional VTs. Bob might comment on impact on reliability of data if phase voltage wanders significantly. 3v in 240 is around 1.5% - how accurate does your data need to be? - the CTs are only around 99% accurate at best.

You could only combine circuits if they are on the same phase (I think)

With 14 inputs for the Iotawatt (derived voltage) and assuming your 11 circuits are single phase then:

Input 1 = mains A
input 2 = mains B
Input 3 = mains C
then input 4 to 14 are your 11 (single phase) circuits.

Maths on the each input on the mains incomer using the appropriate MIN / MAX functions will give you imported and exported on each phase.

Solar on each phase can come from a calculation of the consumption on each phase and the amount imported. IncomingA + SolarA = sum of each phase A circuit consumption.

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There is no difference between direct and derived reference for phase A. It is only phase B and C that can be impacted by large voltage differences from A. So 1.5% variation on two phases would potentially only be about a 1% overall variation.

The AccuCTs are 0.5%.

Based on that feedback…

I downloaded the data from the inverter over the last week. The difference between phase voltages were at its greatest 15.52v (6.7%). Average difference 3.6v (1.5%). It was above 3% for 15% of the time and above 2% for 33% of the time. Considering 80% of my GPOs and Hotwater are on the measured phase, its going to be more accurate than those averages.

I might get the extra plugs installed but only use them if I end up getting a 2nd IotaWatt.