What have I done wrong?

Hey All,

I have my IoTawatt all set up and things seem to be working well. I am in Australia with 3 Phase Power. I am using the derived method for my power. However, my problem lies with the power readings compared to my power meter and solar inverter. Looking at kWh generated, i find that i need to multiply the reading from IoTaWatt for my Solar by 1.79 in order to get within 0.05kWh of the correct reading from the inverter. From my power meter, I have found I need to multiply the IoTaWatt reading by approx 1.65 to get in the correct range. I’ve monitored these values for a few days now and multiplying by these values gets as close to what the actual reading so i am happy.

However, this tells me that I have probably set something up incorrectly with IoTaWatt but I dont know what it is. To confirm, yes I have checked the VT and it is set up correctly I am using the MP-3027. I am using the ECS16100 on my main power supply and the ECS1050 on my other circuits.

Hopefully someone can help me figure out where I have gone wrong.


Have you checked that you have each CT on the right phase, A,B or C ?

It does sound like there is a problem with either phase assignment or CT orientation. Be sure you have read the documentation

There are literally dozens of incorrect combinations of phase assignment and CT orientation. Only one of them will give the correct result. By following the documentation procedure, specifically insuring all of your CTs are oriented the same with respect to source and load, the possibilities can be reduced to six. By insuring you have identified the VT phase A, the possibilities are two, and by observation of the effects of a large resistive load like a hair-dryer or toaster, you can get that right.

When an incorrect phase is specified, or a CT is reversed, the power of that phase is reduced to about half for a purely resistive load and somewhere near half for a reactive load. So if one phase is correct and two not, you will show about 2/3 power or less, which would need to be multiplied by 1.5 or more to be correct.

That sounds like where you are at. Concentrate on the mains, get the VT phase A right, then if possible switch a resistive load on the other phases until you see them change by the nameplate rating if the appliance.

Thanks overeasy - I have doubled checked and confirmed that my CT’s are correct for orientation. I believe I have the VT phase A correct. I just had a play around with switching the values around and saw the power drop by about half, in its current configuration this is the highest power i can get out read out. Additionally whenever I change the phases around, I end up with the reverse symbol displayed. In its current config there are no reverse symbols.

What is weird is the solar reading as well… I am not exactly sure what phase this should be on, as it goes directly to our meter not into the house.

In saying all these, i am a bit of a noob, so may still have something wrong.

Attached are some pictures on my setup if this at all helps.

So for those phases where there is a wall socket, if you plug in a hairdryer or even a 100 Watt incandescent light (remember those?j, by how much does each change as it is turned on and off?

That’s the gold standard. The effects of various configuration errors can be all over the place, including appearing reversed (in fact that’s common), but a hair dryer will only show its full Watts on the correct combination.

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Thanks Overeasy,

I did as you said - I actually used a 1600w heat gun and tested the different areas of my house. I have then compared that to my meter and it is bang on now.

Thanks for the advise!

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I wasn’t at all happy with that.

I’m happy with that.

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