I’ve just installed my IotaWatt and would like to offer a few suggestions based on my experience. Although I tried to read the documentation carefully and plan out my install before making any connections, I still missed a few important points. Hopefully these suggestions will help others avoid the same mistakes.
Document Split-Phase Legs for the Panel
North American panels have split-phase power with two “legs”. These panels have breakers running down two columns. But the leg for each circuit in the panel is determined by the ROW in the panel and not the column. Until recently I misunderstood this important detail. This misunderstanding created problems with two situations in my initial install. For some of the CTs, I had wrapped the CT around the wire from more than circuit but didn’t realize that I had combined signals from Leg A and Leg B (resulting in subtracting the power of one circuit from the other). And I had a similar mistake by combining signals from Leg A and Leg B via headphone splitters (into one input of the IotaWatt). I cleared up this mess by creating an Excel spreadsheet showing the Leg for each circuit on my panel. This post on stackexchange provides a good explanation of the layout of the legs in a panel and I think it would be useful to include similar info in the IotaWatt documentation:
Allow Negative Power
I recommend that you enable “Allow Negative Power Values” for all inputs when doing your install. This setting helps avoid accidentally combining inputs from different legs.
CT aligned to VT
I recommend that you orient all CTs to be consistent with respect to the VT and oriented to generate positive power. If you have a solar input generating positive power and want your loads to appear as negative power, can enable the “reverse” option in the VTI input configuration to make all loads appear as negative power.
With “allow negative power” enabled for a CT input, the sign of the power reading for a CT (input) will be determined by the orientation of the CT with respect to the Load AND it will depend on which power Leg the VT is plugged into. To keep the CTs all aligned with the VT, all of the CTs on one Leg will be oriented toward the Load and all of the CTs on the other Leg will be oriented toward the Source. More specifically: If the circuit is on the same leg as the VT, orient the CT toward the SOURCE. If the circuit is on the opposite leg from the VT, orient the CT toward the LOAD. For “pure 240V” circuits, you will connect a single CT to one Leg of the circuit and it should follow the same protocol : if a CT on a 240V circuit is connected to the same Leg as the VT, orient it toward the source. For “120V/240V” circuits, you will connect CTs to both Legs and the CTs will have opposite orientation. The CT on the VT leg should be oriented toward the source. With “allow negative power” enabled on your inputs, you can test each CT to verify they oriented correctly before combining anything.