An experiment. Here is the power trace for the Studio for yesterday:
Not a lot going on up there as it is currently unoccupied - just the fridge cycling on and off. The black line is general power outlets, red is the aircon circuits + lights and blue the oven/stove.
From midnight to a little after 8AM the off-grid inverter was supplying power. I had the voltage reference set for each (RED, WHITE, BLUE) to use the off-grid VT reference.
At 8:05AM my off-grid system cut over from supplying its own power to passing through grid power. Not long after that we can see the flat line appear, most obvious in the black line power trace.
So a little while later (~ 9AM) I changed the voltage reference for all three CTs to instead use a derived BLUE voltage reference (RED + 240°).
This resulted in a completely plausible power trace. Grid power is being passed though, so it’s not entirely surprising.
Later in the day (5:50PM) the off-grid inverter switched back from passing though grid power to supplying its own power. I made no change to the voltage reference set up, it was still using the derived BLUE voltage.
Even so, it did not seem to have any issue with reporting plausible power numbers. Now they will be out by a little because there would typically be a 10+ V difference between grid and off-grid voltages.
You can see the reported power numbers for the fridge jump up a little after 6PM, and that would be I presume because the IotaWatt is calculating power using a voltage reference which is a bit higher than it actually is (it will be circa 10 V higher).
Here is the power and PF traces for that black power line (WHITE) phase. PF for the other circuits likely won’t make much sense given power draw is so low:
I find this interesting.
If we compare the midnight to 8AM period with the 6PM to midnight period, there is very little difference in reported PF, even though the former used the VT reference and the latter the derived voltage reference.
I’m no engineer, let alone an electrical one, but does this evening power and PF trace suggest the off-grid inverter’s output maintains synchronisation with the grid (at least while ever the off-grid inverter has a grid input signal)?
It would seem, at least for these Studio circuits, to be a reasonable workaround until hopefully we can resolve the off-grid utility pass through voltage reference issue.
Naturally any time the grid power goes down (around here that’s a matter of when, not if) this means there won’t be any data but at least I have something.
However, I’ve replicated the same thing for the Mancave and unfortunately I don’t get the same outcome.
It should be almost be a replica of the Studio, with one circuit showing the regular power cycling of a fridge while the other circuits have very little consumption unless I’m down there doing stuff and/or have the aircon running. I need to do more investigation of the mancave set up.
All the circuits for the primary dwelling currently being monitored don’t use the off-grid supply so they are working well with their grid voltage reference.
I would like to cover some (if not all) of those primary dwelling circuits which are powered by via the off-grid system at some stage, hopefully by freeing up a CT or two by consolidating circuit monitoring for the Studio and Mancave.