Distinguish Consumers from Producers in Solar Sub-Panel


#1

I have the Solar Sense with the 2 pairs of CTs. I have a 400A safety switch where the Sense is installed like so: (The Sense CTs barely fit over the 350 MCM copper cables)

This is on the outside of my house. To the right of the switch is the utility meter, to the left is a 400A automatic transfer switch that feeds 2 200A sub-panels in the basement on the other side of the wall (and a 20kw Diesel generator is also connected to the transfer switch, but not at the time the photo was taken).

You can just make out the sense antenna sticking out the bottom of the safety switch. I have a detached shop building located 200 feet away, which contains a 3rd sub-panel, which includes 6 breakers for a 20kw micro-inverter based solar array (80 panels). Here it is:

The 6 20A breakers at the top are for the solar strings, and all the lower breakers are loads in my shop.

So what happens is that EVERYTHING that goes on in the shop sub-panel is going through the Sense solar CTs. So what happens is that anytime a device in the shop uses power, it gets subtracted from the solar total.

So would it be possible for sense to distinguish ingress vs. egress on the Solar CTs and not count the egress (loads in the shop) towards solar production, but instead treat them as loads just like everything I got hanging off the 2 sub-panels in the main building?


#2

Nice setup – thank you for sharing the pictures!

You are right that since your solar feed is actually solar minus the load in your shop (if we understand your description correctly), so it won’t result in an accurate metering of what is going on. And, for the case where your solar is off or producing less than your shop load, when the current will flow in the other direction – it would make sense for Sense to realize this and not count it as negative production! But, that still won’t help you while solar is producing since we will just see solar production minus the shop consumption at that point and won’t really have a way to pull these apart.

We’ll keep an eye out for this sort of thing to see if there are other installations like yours and figure out if we can better account for this in some future software update. Hope this helps!


#3

Appreciate the feedback. Here’s a diagram of my setup:

As you can see, my only option for installing sense where the CTs can reach both the regular house load and the solar, is in the disconnect switch where the 2 come together.

Since sense can pull apart loads in the house based on power fingerprint/signature, why can it not do the same for events across the Solar CTs?

I would think my 6 Micro-inverter strings would have a very distinct signature, with current flowing in only one direction and only during the daytime, with the intensity typically increasing until noon, and then slowly decaying again.

Everything else, on the other hand, would be flowing in the opposite direction, and would always represent the loads connected to that sub-panel.

So why not apply the sense device algorithms to the Solar CTs just like it is already doing for the load CTs?


#4

Would an option be to purchase a 2nd sense (with no CTs) and dedicate it to pickup the Solar only?

Going that route, I could redo the config at the house and move the main CTs to monitor all power consumption from the meter base by placing them as follows:

And the “remote” solar CTs would then wrap around the 6 circuits for the solar system as follows:

I’d have to extend the wires a bit, but that would not be a big deal. If I really wanted to do it perfectly, I’d add a subpanel dedicated to the solar arrays, but I’m hoping not having to go that extent. Btw, the bus bar in that panel is rated for 225A and the main breaker has been swapped out for one that is 150A. So 225A * 1.2 = 270A. 270A - 150A = 120A. So I’m meeting code with my 6 x 20A solar breakers in the panel, barely (and passed inspection).

So in essence, the 2nd Sense unit and pair of solar CTs, would be tied to a single account in the “cloud” and show consumption and solar production on the same timeline. The shop is on the same LAN as the house and the AP there is on the same SSID as the APs in the house. So the 2nd sense would just be a means of extending the current picked up by the solar CTs back up to the cloud.

Here’s a pic showing the shop building relative to the house. So there is no way to physically connect the main CTs to the service entrance feed and the solar CTs to the solar only.