Sorting out an Australian three-phase installation


&That was productive. It looks now as if the mains are correct. That said, I think the other circuits are still pretty much scrambled with respect to phase assignment and/or CT orientation. At a minimum I would expect the AC to read fairly close on all three phases. Not sure what the load is in the garage, but shouldn’t be reversed and the PF on 1 and 3 are questionable.

One thing that the light experiment shows is that voltage on the three phases is probably not as consistent across the three phases as some other derived reference installations. That is probably why the light is 120/131/139 watts across the three phases. If you want greater accuracy you may want to consider using direct reference after you get the other unit.

In the meantime, you will need to somehow determine the phase for the branches that you have. Can you get a picture of the back of the board where they all connect? Specifically, I’m interested in what’s going on behind this:


I will post a photo shortly but most Australian Boards are setup so that there is NO exposed wiring.

My initial thoughts were (and please change/reset if you have a different plan).

a) Create a table that assumes 2 x IotaWatt, lists the IotaWatt inputs, VT or CT, Circuit measured and Phase and CT Orientation.
(I can post this and will get to you amend as you see fit).

b) Other than the 3 phase MAINS, remove the other CTs for now.

c) Run some controlled testing against an unloaded circuit (other than say the 150w light).
Ideally they all measure the same usage within a few watts, but it would be nice to know that the CTs are all reading as expected. I can continue this with the new CTs that should be here in the next day or so.

d) Option 1: If I can get to the back of the board (which I doubt) we can use multimeter/voltmeter to trace circuits.
If this is likely to happen I will get a electrician in to assist but having the table to document in will be invaluable.

d) Option 2: I shutdown power to a minimum (eg MAINS A/B/C and enough for a VT then use my phone to provide WiFi to IotaWatt. Run something on each of the Circuits with a roving CT and see where it pops up (Mains A/B/C) and document the phase that phase is ok.

e) when the new IotaWatt arrives it will have 2 x VTs. (Whats the best way to test them against my current VT or is the plan to go with Phase A and C (as thats most used) and if they read the same we assume B is good?

e) wire up both units/inputs based on what we have learned

f) restart the inputs and feeds and give it a week.

According to the meters we are pretty consistently sitting on 44kw used per day and making about 4kw on a sunny day. Unless we use the Sauna but its rare.

Thoughts/comments/preferred direction>

EDITs added picture
note that largest cable is 6mm so I could get away with a smaller CT


I think this is the next step.

Introducing another IoTaWatt before this one is reconciled would just compound the problems. One thing at a time.

Does this come close to the IoTaWatt Mains total now?

If the mains prove out with the meter, the next step is to sort out the various branch circuits.


Read time for me is 10:00 which is UTC 0.00 so will get both done in about 30 minutes.

I am talking with Tristan from emoncms as the daily feeds (kwhd) went away and they are likely to be reset. I am going to see if I can make a daily feed from Iotawatt using the MAINS total and delta.


That’s way to complicated, and I trust the IoTaWatt datalog more for this anyway. You can get the current kWh to date for any input or output from the graph app. Just run the graph app and click on the desired input or output under the “energy” tab. Here’s my meter:

The max value at the bottom is your present “IoTaWatt Meter” reading. You should record this at the same time as the physical meter reading. There is no time latency. Everything is now.


Thats a much better and more reliable way to do it.
Ideally I would leave it another 24 hours (as we moved CT for Mains 3 yesterday) and it might be good to give it some additional time.

Graph is below. I have left the csv in there so you can see both the Mains and Solar totals.

Actual reads from the meter will go here shortly:
As mentioned, the solar is pretty much accurate.

Date Mains Meter
07/08/2018 27,737 53
08/08/2018 27,790 25
09/08/2018 27,815 54
10/08/2018 27,869 44
11/08/2018 27,913 46
12/08/2018 27,959 76
13/08/2018 28,035 44
14/08/2018 28,079 69

So at present it seem to be under-reading but it might be that with the change to Mains3/C we are now ok. Lets give it another 24 hours.


Here are the readings updated for today. Keep in mind that its really only the last 3 that we think we have configuration correct (so last 2 readings as we are trailing by a day).

We are now much closer but only reading 80% of actual.

I will get out the multimeter and take a quick look at voltages for A/B/C and post readings.

Date	Mains	Meter	IotaWatt
07/08/2018	27,737	53	33.08
08/08/2018	27,790	25	29.69
09/08/2018	27,815	54	52.55
10/08/2018	27,869	44	33.88
11/08/2018	27,913	46	38.77
12/08/2018	27,959	76	58.47
13/08/2018	28,035	44	29.41
14/08/2018	28,079	69	54.23
15/08/2018	28,148	35	27.02
16/08/2018	28,183	0

Added the graph for completeness.

@overeasy Please let me know if you want/need any of the serial capture log files. I have continued logging for now but would like to clean that up eventually…


There’s still something wrong. Could you do that plot with the three individual mains instead of the total and show the CSV?


I thought this might be a good start.

Will plot a second one with Mains/Solar Removed. I can turn off the delta if you want overall totals rather than daily.

2018-08-09 10:00:00, 52.55, 3.12, 11.2, 11.6, 29.7
2018-08-10 10:00:00, 33.88, 3.07, 10.6, 7.4, 15.9
2018-08-11 10:00:00, 38.77, 3.18, 8.2, 15.3, 15.3
2018-08-12 10:00:00, 58.47, 3.26, 16.7, 15.6, 26.1
2018-08-13 10:00:00, 29.41, 3.20, 9.0, 6.5, 13.9
2018-08-14 10:00:00, 54.23, 3.09, 15.3, 13.9, 25.0
2018-08-15 10:00:00, 27.02, 3.29, 7.7, 8.1, 11.2
2018-08-16 10:00:00, 22.82, 2.90, 6.7, 6.8, 9.3
2018-08-17 10:00:00, null, null, null, null, null

I will update both sets of graphs after 10:00am
I will include the CSV from the graph
I will also add the Meter Stats
According to my timestamp you were happier with the install (change and reverse CT for Mains3) from 15th August, so we maybe have 3 decent days.


Updated reads and graphs as of 10:00 so they should line up with prior readings.

As per previous I would only be going from around the 14th onwards and would take earlier with a pinch of salt due to CT on Mains3

Meter Actuals vs Iotawatt

Date	Mains	Meter	IotaWatt
07/08/2018	27,737	53	33.08
08/08/2018	27,790	25	29.69
09/08/2018	27,815	54	52.55
10/08/2018	27,869	44	33.88
11/08/2018	27,913	46	38.77
12/08/2018	27,959	76	58.47
13/08/2018	28,035	44	29.41
14/08/2018	28,079	69	54.23
15/08/2018	28,148	35	27.02
16/08/2018	28,183	34	25.10
17/08/2018	28,217	50	37.66
18/08/2018	28,267	0	


Graph CSV Output

2018-08-11 10:00:00, 38.77, 3.18, 8.17, 15.28, 15.32
2018-08-12 10:00:00, 58.47, 3.26, 16.72, 15.63, 26.12
2018-08-13 10:00:00, 29.41, 3.20, 8.99, 6.53, 13.89
2018-08-14 10:00:00, 54.23, 3.09, 15.30, 13.91, 25.02
2018-08-15 10:00:00, 27.02, 3.29, 7.70, 8.11, 11.22
2018-08-16 10:00:00, 25.10, 3.31, 7.34, 7.01, 10.76
2018-08-17 10:00:00, 37.66, 3.15, 9.99, 8.08, 19.59
2018-08-18 10:00:00, null, null, null, null, null

Please let me know if you want a seperate graph of Mains1/2/3 with no delta or anything else…

EDIT: update graph & numbers with extra day


So right, last three days, IoTaWatt total power has been ~80% of meter power.

To recap where we are:

Given the spaghetti wiring, it has been difficult to determine the phase/load relationship and we’ve been concentrating on trying to get the mains correct. We determined with resonable certainty that the VT was connected to Main1 here. So Main1 is phase A.

We determined that the hot water heater was connected to Main3 here.

We determined that Mains3 is phase B using unity power factor of hot water here. So by elimination Main2 is phase C. This is somewhat supported by the order in which the Mains are presented to the meter here. Note that the sequence right to left on the back of the meter is B, A, C. I don’t know if 3ph meters work like 3ph motors, but if so wiring it A, B, C would have made it turn backwards, so I’m guessing that without color codes, they just connect them up arbitrarily and if it goes backwards, they swap A and B.

So the last piece was to insure that all of the CTs are facing the same way with respect to line/load, and that was corrected. So now I believe that the mains measurements are setup correctly. Yet the readings have been ~20% low for several days.

Going Forward:

Expectation for the mains with derived reference is at least within 5% hopefully better. So I’d like to continue to pursue that 20% difference. My suspicions, in order of interest, are:

  1. One or more CT is reporting low.
  2. There may yet be an error in the configuration/setup.
  3. There are gross voltage deviations between the phases.
  4. The meter is wrong.

So to further explore the obvious #1 there are a few things that can be done.

Take all of the CTs, configure then for phase A. Mark each with a unique number using a felt tip marker, and clamp them on the Main1 line at the same time. Observe the power recorded on each and note any outliers. Do this at both lower and higher power. Also note variations in power factor when above a few hundred watts. Reinstall and configure with the most consistent CTs on the three mains. Wait a couple of 24hr cycles and see if there is better agreement.

If you have a decent true-rms clamp on ammeter like a Fluke, you can configure outputs for each of the mains with Amps as the units, then compare the meter to the IoTaWatt Amps. They should be within 1% on all phases.


My suspicions, in order of interest, are:

One or more CT is reporting low.
There may yet be an error in the configuration/setup.
There are gross voltage deviations between the phases.
The meter is wrong.

I agree 100% with your thoughts and would like to propose the following steps - if you think its ok as its a tweak to your process:

  1. Identify 2 loads (ideally around 100w and 1000W but whatever we can find).
  2. Try and get an independent measurement to validate what they are actually pulling.
  3. Remove all the CTs (video process so I can see exactly where/orientation they were on.)
  4. Loop through the the CTs on the Phase A/Circuit with the load (and just that load)
    a) are they all reading the same measurement (record any deviation and sort/ the CTs)
    b) is that measurement correct to what we know it should be (eg 100W measured vs 100W load)
    c) assuming we have consistent CTs, repeat the process for a circuit on Phase B & C
    e) report back.

I know this is slightly different to running agains MainsA but it means I can control the power draw and there is one less variable.

Other notes:
I have received my next batch of 10 x SCT-013 but I think it will be a week or two before I get the next IotaWatt and 2 x VTs from the UK.
I will source a clamp True RMS meter

If you are ok with this then I will proceed - if not I can measure the other way but figured it was better to at least start with an idea of how accurate our CTs were before we then spent days with each one measuring mains.


CThat’s kind of complicated and introduces some new variables. Your mains cables are real long, so it would be fairly easy to clamp a bunch of CTs to the same cable and see if they are in agreement. I’m looking for outliers more than poor calibration.

I think most, if not all of them, will be accurate. I’m looking for something that is bad. The last two problems resolved this week involved CT issues. One must have been a problem with installation because it resolved. The other was a broken core in a ct causing it to read low. So I’d like to check yours for outliers and go for the hat trick.


OK - lets go with simple first and then add steps as needed.

  1. Remove all the CTs (video process so I can see exactly where/orientation they were on.)
  2. Add as many CTs as practical to Mains A Load
  3. Measure and log them with small and large loads
  4. Report back.


@overeasy I will proceed and do the full test in daylight tomorrow so we know what the CTs look like but…

That said there is a chance for sauna/air con tonight and I have my doubts about CT for Mains1
Why? Was looking for spikes/oddities in the voltage vs Mains ABC and this is recurring theme (see graph below) - Mains 1 is always low… Could be our dud…

Sticking a brand new CT on it for now.

Mains1 reads low vs Mains2 and Mains3. Also voltage shows odd measurement in same period


so…i was wrong…its something else and will do a full CT test as discussed.

This is with 3 x new SCT-013 100A on mains1/2/3 and cranking up the AirCon.
Same weirdness on Mains1


This is consistent with other unexplained issues we’ve encountered. It explains the 1300 watt hair dryer and the lower reading on mains1 during the light bulb test. Also, pretty much aligns with the 20% meter disparency.

At this point it’s necessary to rule out a problem with the IoTaWatt channel 1 being used for that CT. I’ve not had any issues with quality but what we are seeing could be a low burden resistor. So can you swap inputs 1 and 2, swapping the phase assignments at the same time, then crank the AC and see if the low value stays on 1 or moves to 2?

I think we are close to solving this.

UPDATE: This also looks what would happen if Mains1 has the wrong phase assignment. As I recall the assignments were:

Mains1 = phase A
Mains2 = phase C
Mains3 = phase B

Can you verify that’s the current configuration?


Mains1 = phase A
Mains2 = phase C
Mains3 = phase B

Can you verify that’s the current configuration?

This is indeed the current configuration!

I have made the change and inputs are as per below.

I will line up the CTs for some comparison reading testing in a day or so.



Really just need a graph of the three mains through an AC cycle.


Its coming :slight_smile:
Just waiting for the washing machine to finish - 5 mins