US Split Phase Setup (Software)

Hello and first of all, thank you VERY much for this! It’s an amazing tool that brought me endless enjoyment over the past 2 weekends :). I am going to get it working and then integrate into my grafana/homelab setup which I am very excited about.

However, here’s a quick question. For testing purposes I connected 2x200A CT on main, 2x100A to 2 loads (furnace/HVAC/fan and a living room), and 2x50A to heat pump (1 on each leg). I wanted to test everything before I prettify all the wires and close it up. Here’s my software setup.

However I am unsure about derived three-phase. I am 97% sure I have a split phase system (here’s the picture).

Do I need to enable derived 3 phase power? If I don’t then my pf looks awfully low on one of the legs. And if I do, there’s no option for 180 degrees for some reason. How come?


Hmm it might be correct as is actually. When I turn on microwave it goes from 300watts to 2000 watts image

That looks reasonable. It’s unlikely you have anything other than a standard US split-phase service.

Ah thank you very much. I was concerned that my pf was low, but it looks ok now.

Do I have to worry which way CT is plugged in, or is that only for 3 phase where I have to worry?

For split phase systems, IoTaWatt will automatically numerically reverse when required. It is doing that for all of the circuits where the reverse symbol is displayed ↺.

If you reverse the VT in it’s socket, you will see those four reverse symbols disappear and then the HeatPump_2 will show the reverse symbol whenever it’s value is non-zero. That’s because the orientation of the CTs is relative to the orientation of the VT. In other words, there is no absolute right or wrong way.

The orientation of the mains CT is the exception when there is a PV system and it’s important to see when power is exported to the grid. In those cases, the “allow negative power value” box is checked in the mains CT configuration. The CTs can be reversed to be correct if needed or the “reverse” checkbox in the configuration menu can be used to reverse it numerically.

Thank you very much! That makes sense. The documentation was a bit confusing with regards to if I need to change it.

This is very interesting data. Bryant 80 runs a fan every hour for 15 minutes to circulate air. It runs at 270 watts which is a bit higher then expected but maybe ok. However when the heating pump runs the fan power goes up to 480 watts, which is so strange. Time to investigate.

I cannot comment on your particular furnace, but my Lennox furnace has an ECM blower that can vary the speed (and power consumption) depending on what mode its running in. Fan “On” is reduced speed from heating mode in default configuration.

That makes sense that it runs on two different speeds… but that’s one powerful fan though. 500watts? wow