Hoping someone could help...

[soby]

Neither meter. It refers to the meter put by utility to track total production of the PV so that MA can give credits for total production of solar as well. See blue circle in picture below. Capture1.JPGif not clear, Please also refer to the post wilow made to which you responded that it is clear (re your post, #18). my point is that meter can only read total production if scenario #1, in my previous post is what is happening.

gjohn,
I stumbled upon this issue with the critical loads panel and the SMART energy meter back in May: https://www.solarpaneltalk.com/forum...s-backup-loads

I am your guinea pig because I convinced my installer to add an APC UTS10BI: https://www.apc.com/shop/us/en/produ...240V/P-UTS10BI.

The backup loads from the StorEdge inverter feeds the generator input of the APC automatic transfer switch. When the grid is up, the backup loads feed is unused. When the grid goes down, the transfer switch SHOULD start sucking power from the LG Chem battery. I say should because it's not all up and running yet (long story but at least I'm generating power!). I hope to be able to test this setup in about a month pending an RMA replacement battery from LG Chem (again, long story).

[Ampster]

I don't see a post where scenerio #1 is described. Do the production meter and the energy meter report the same numbers for the same period? Do you get a production number from the SolarEdge that you can compare to the other two meters?

[gjohn]

When you say "production meter" are you referring to the one inside the SolarEdge or the one labeled "Energy Meter" on that diagram. I can tell you that those two meters will read different values depending on what the loads are drawing.

Neither meter. It refers to the meter put by utility to track total production of the PV so that MA can give credits for total production of solar as well. See blue circle in picture below. Capture1.JPGif not clear, Please also refer to the post wilow made to which you responded that it is clear (re your post, #18). my point is that meter can only read total production if scenario #1, in my previous post is what is happening.

[Ampster]

When you say "production meter" are you referring to the one inside the SolarEdge or the one labeled "Energy Meter" on that diagram. I can tell you that those two meters will read different values depending on what the loads are drawing.

[gjohn]

I may not understand your wiring. The only one I have seen is your hypothetical one withe the hypothetical transfer switch. I couldn't open
the other one.

this is the wiring diagram for Storeedge, that both me and willow have. in willow's case there is a production meter on the line going to load. What i still dont have total confirmation from this forum is if the critical load is fully powered by the grid or if the solaredge is combining the power from grid and PV and then realllocating the power to the critical load (backed-up) and noncritical load
https://www.solaredge.com/us/solutions/grid-backup#/. if the former, it is clear why the production meter will faithfully capture the total solar output. if the latter, no one has explained yet why the production meter will see the full PV output.

[Ampster]

What did you find out when you put the clamps on? The point of my post was for you to observe the power coming from the SolarEdge inverter and compare that to the SolarEdge . Also observing the power going to the sub panel should give you some insight Don"t expect the load on the critical loads subpanel to be balanced. Each leg could be different, whereas the output of the SolarEdge should be balanced.

I may not understand your wiring. The only one I have seen is your hypothetical one withe the hypothetical transfer switch. I couldn't open the other one.

[gjohn]

Either one. One should be your subpanel consumption, which might not be active unless you are on backup power. The other should be production.

I dont see how your phrasing in this post is correct. If you look at what Willow sent, the subpanel is always active from solaredge because that is the critical load that has no other line connection to get power other than from one of the two output lines from solaredge, while the other non-critical circuit panel is directly connected to solaredge and the utility connection. And finally if the current in both the lines are the same, the power (I*V) in those lines also will be the same because the voltage is standard 120/240 and that means when the solar is producing just enough for all the house loads, that equates to the same amount of power utilized by both critical and no-critical loads which is absurd. the only explanation that is so far seem to make sense (your's is not yet making sense to me) is from willow who thinks the critical load subpanel is purely powerd by grid.

[Ampster]

Either one. One should be your subpanel consumption, which might not be active unless you are on backup power. The other should be production. You could also try it on your service entrance and see net production.

[gjohn]

Place a current clamp on the output from the SolarEdge and you will see that it should be the same as the production meter on the SolarEdge.
..

Thanks for that insight. which output? i assume the line from solar edge that goes to main panel? - remember there are two accessible "outputs" from solar edge: one that runs to main panel and another that runs to the sub-panel with critical load as Willow showed using his installation.

[Ampster]

@willow -You could be right, and you may have indeed solved the problem that no one else so far did! - ie solaredge is normally allowing the grid powering the to power the critical-load subpanel fully, and hence the production meter will indeed calculate the power generated in full. I have not find any documentation yet on this front. I thought solaredge was splitting the PV to both critical and no-critical lines under normal circumstances. Anyone else has a different opinion?

You were correct that the power from the SolarEdge was being split. It was not the SolarEdge that was splitting the current, rather the loads that were splitting the current. In the situation where there is generation that exceeds the load the grid presents as a load and the current from the inverter is split between the grid and the other loads behind the meter.That was being done after it leaves the SolarEdge inverter.
If you want to document it you can perform this simple test. Place a current clamp on the output from the SolarEdge and you will see that it should be the same as the production meter on the SolarEdge. Place the clamp on the legs after the meter and you will see that the result is Production less Consumption. In other words, the Net result of production less consumption.

I regret that I was able to articulate it as clearly as @willow but at least you are off the tangent of trying to solve the problem with a transfer switch..

[Ampster]

..... @Ampster /anyone: do you know how that happens ? In my mind that meter is only seeing the current (i) and meter-resistance(R) in that line of non-critical load and then using the "equivalent" of i*i*R to calculate power but is then ignoring the other subcircuit with the critical load from a physics standpoint.

It is all about where the CTs are placed hat measure the current. SolarEdge uses internal CTs but it may also be able to use external CTs like my Outback Skybox can. I am glad the discussion has moved from whether a transfer switch will work to a discussion about how best to measure production.

[gjohn]

@willow -You could be right, and you may have indeed solved the problem that no one else so far did! - ie solaredge is normally allowing the grid powering the to power the critical-load subpanel fully, and hence the production meter will indeed calculate the power generated in full. I have not find any documentation yet on this front. I thought solaredge was splitting the PV to both critical and no-critical lines under normal circumstances. Anyone else has a different opinion? If not, i will tag this as solved. Thanks again Willow, that is indeed a fantastic pointer, which makes an ATS unnecessary for that reason in MA for solaredge (hope someone can confirm this for sure).

[willow1]

gjohn, think the critical loads are only fed from SE and the battery when the grid is down. When the grid is up, the main load or grid feeds these circuits (otherwise there would be no power to these circuits when there is no power being generated by the inverter, and the output to the main load would be reduced as well).

[gjohn]

@Willow - that was superhelpful. So the grey meter, despite it being on the main panel load which ONLY supports the non-critical load (because you confirmed the subpanel supporting critical load is only supported by solaredge) is able to calculate the total production power. @Ampster /anyone: do you know how that happens ? In my mind that meter is only seeing the current (i) and meter-resistance(R) in that line of non-critical load and then using the "equivalent" of i*i*R to calculate power but is then ignoring the other subcircuit with the critical load from a physics standpoint.

Forget the transfer switch for the moment. Also, I think Kirchoffs law is confusing the issue. Do you understand why the meter only sees the net? You would have to take the load somewhere else, for example behind a separate meter, and then all your production will be seen by your main meter.

.

[willow1]

gjohn, see below:
1. which of the meter is the total solar measurement -i assume the grey NOT the black? and is that meter installed before the connections go to solar edge? I assume it is after.
Yes, the meter second box from the left is the total output measurement. It is after the SE which feeds the combiner box (third from left) along with the the AC output from the Enphase microinverters.
2. on your StoreEdge picture, which line is the critical load and which one is the main panel load?
The critical load feed is the one on the right of the picture (lower of the two feeds to the right). The main panel AC feed is the feed on the left which then goes to the right of the picture on the top.
3. On a monthly basis does the reading from your TOTAL meter approximately equals what is reported by Solaredge? If not, could you please quote some numbers for one or two months, if possible?
Its a bit complicated given that that I have to add together the output from the SE monitoring as well as the output from the Enphase Envoy monitoring. In total though, they are roughly what is reported on the total output meter. There is a two month delay in the Eversource SMART billing / credits, but they do approximate what the SE and Envoy monitoring apps each report.
4. is your crtical load panel put on a seperate fuze box that is only powered by Solaredge? ie there is only one incoming connection to that panel, and that is from Solaredge.
The critical load sub panel and breakers are powered only by SE (from the battery) when the grid is down. If the grid is up, AC power is used from the PV or from the grid if not generating PV at the time. Here's a link to photos of the main / subpanel with the subpanel cover open and closed.

https://1drv.ms/a/s!AurfEsR2BLA4geVO_2xvXBmoEdicEg