Solar startup for CTs on other than solar circuits

I have been successfully using the Main CTs on my second Sense to directly monitor a hot water tank. This is yielding very interesting comparative data, namely: Sense-native detection vs Sense-native ground-truth monitoring.

Meanwhile I’ve had that same Sense’s Solar CTs (one of them only) on a 120V window air conditioner to give me some ground-truth data on that. It “works” but the calibration is off.

It seems though that the Solar CTs are bad … the other CT has zero output when clamped to the same wire. After testing with a Fluke and comparing to my primary Sense signals, I determined with Support that they need to be replaced.

Meanwhile I have just installed another Sense (Solar) elsewhere, for a friend.
In that solar-less setup I put the solar CTs (both this time) on a 208V air conditioner.
All the signals seem to check out in realtime (vs. a Fluke) but the friend is expressing concern about the “calibration” phase for solar. There are messages in the UI to that effect.

So the question is: What is the full startup/calibration sequence for solar if you specifically aren’t using the solar CTs to monitor solar inverter outputs? Are there actually expected nighttime cycles where 0w output is needed for calibration? Is there some kind of offset established based on the inverter load (capacitance)?

I see that “Sense needs at least 500W of total solar production” during the “calibration step” but I can’t find much beyond that.

The ultimate question is: What is the startup sequence if I want to put the solar CTs on something other than solar?

BTW: In the case of my friend’s panel, the 4 CTs and cables are really jammed in since the panel is very small and I am loathed to have to touch anything now. Meaning: If there are options, the ideal startup procedure should not involve having to clamp/unclamp after the initial install.

[I’m also gnawing at the heels here hinting at a non-solar mode for the solar CTs!]

@ixu: Did you get any clarity on this? Anything you’ve learned to share further? I’d like to use the solar CTs to check on consumption from mini-split heat pumps (which the Sense has trouble seeing independently, since they are inverter-driven/variable).

@asa.hopkins

The details of solar startup on non-solar devices are still a little unclear but I think you won’t have issues if you clamp the solar CTs to your mini-split circuit. Even if the absolute calibration is off (which I have experienced) you will get a clear picture of your mini-split usage.

I’m guessing, but if you put your mini-split in a non-variable mode (heating and constant fan using >500W) you’ll have the best chance of success with the startup. I have cheated the on/off solar startup requirements (i.e. “Switch your inverter on/off”) by, rather than switching the device on/off (e.g. hot water heater), quickly unclamping/clamping the CTs … though of course this is sub-optimal.

BTW: You can “test” your solar CTs on other-than solar by clamping them on the Mains and mirroring that input. That way you get a clear picture of the calibration, literally, when you view things in the Power Meter.