RESOLVED - IoTaWatt kWh reading much lower than power company reading

It’s all starting to make sense now - when I hooked the DSO up initially I realised the MP2037 was 180 degrees out from it’s respecting CT phase, so I swapped it over on the DSO and didn’t think any more of it!

It also did occur to me that they might have chnaged the MP2037’s supplier and that it was wired back to front, but alas when I looked, it appears they went out of their way with a keyed connector so that it can’t be swapped over on the plug. I guess this was only done this way as they are using the same parts for their DC and AC plugpacks and there’s no “right” way with AC.

That was what confused things even more - the reverse arrow ↺ never appeared at any time when I had it hooked up incorrectly.

I guess I had done a very good job of confusing my poor IoTaWatt (not to mentioned myself)

Thanks for the explanation as well, It’s been over 20 years since I studied any electrical theory at uni and it’s slowly coming back.

Now i can move on with getting the branch circuits added and my other 2 IoTaWatts installed as well - I have two subpanels, one for the pool and aircon, and another for our granny flat. It’s probably overkill but hey, the more data, the better.

Thanks again!


Ok, just to clarify it in my mind, the actual problem is that the VT is 180 degrees out with respect to the IoTaWatts “A” phase, is that correct to say?

At the risk of appearing pedantic, the IoTaWatt A phase is, by definition, the VT. The CT on the same phase as the VT should produce a current signal that is in phase with it. So if your CT is reversed with respect to the VT, it would be 180 degrees out of phase.

I wouldn’t necessarily characterize that as a problem though. It should still read the correct power value, but will be negative if you have “allow negative values” checked. Same for the other two.