Adding SolarEdge inverter to existing SE PV+battery system

[Zee]

Trying to wrap my head around the 120% rule in this case.
Specifically, by adding 40A, is there a risk of overloading feeder conductors or sub panel?
My question pertains to how the Back Up Interface works. That confuses me.

Background:
Existing SolarEdge PV+BATT system from 2020/2021.
-SolarEdge Energy Hub 7600 INV
-LG 16 kWH DC battery
-SolarEdge Backup Interface (BUI)
(See inline image, also attached as file)

Plans:
We want to add about 9.6 kW of PV.
Logical choice seems to be to pair it with a SolarEdge Energy Hub 7600 inverter.
How can i do this so I don't overload any existing feeder conductors, and in a Code compliant matter?
Specifically, I am forgetting how the SolarEdge BUI (Back Up Interface) works.
As you can see I simplified what the BUI does on the SLD below.

Can I add 40A of inverter output to the BUI?
(it can take 3@40A)
I.e. is that going to add to the (E) 40A of PV plus the (E) 110A from main breaker upstream and then feed 40+40+110A (190A) to the (E) 125A rated sub panel?

(shouldn't, right?.... because then the (E) 40A+110A (150A) would be a problem already)

Otherwise, I am fairly confident we are good vis a vis the MSP.
( It is a MBO main brkr. only panel, so no distribution and no busbar, so no 120% rule.)

 

[BackCountry]

Trying to wrap my head around the 120% rule in this case.
Specifically, by adding 40A, is there a risk of overloading feeder conductors or sub panel?
My question pertains to how the Back Up Interface works. That confuses me.

Background:
Existing SolarEdge PV+BATT system from 2020/2021.
-SolarEdge Energy Hub 7600 INV
-LG 16 kWH DC battery
-SolarEdge Backup Interface (BUI)
(See inline image, also attached as file)

Plans:
We want to add about 9.6 kW of PV.
Logical choice seems to be to pair it with a SolarEdge Energy Hub 7600 inverter.
How can i do this so I don't overload any existing feeder conductors, and in a Code compliant matter?
Specifically, I am forgetting how the SolarEdge BUI (Back Up Interface) works.
As you can see I simplified what the BUI does on the SLD below.

Can I add 40A of inverter output to the BUI?
(it can take 3@40A)
I.e. is that going to add to the (E) 40A of PV plus the (E) 110A from main breaker upstream and then feed 40+40+110A (190A) to the (E) 125A rated sub panel?

(shouldn't, right?.... because then the (E) 40A+110A (150A) would be a problem already)

Otherwise, I am fairly confident we are good vis a vis the MSP.
( It is a MBO main brkr. only panel, so no distribution and no busbar, so no 120% rule.)
View attachment 2569692

Does the 125A backup loads have an upstream OCPD? It should, and solves the problem you’re asking.

The BUI can take (3) 63A breakers (they’re a weird CHINT breaker) for their 11kw inverter.

The BUI is rated at 200A, it’s inside of a “breaker sandwich” meaning that your backup loads must have an OCPD.

 

[Zee]

Thanks BackCountry.

No, there is no main breaker in the backed up 125A sub panel.
I will see if that is an option.

(BTW - This older BUI can take only 3@40A brkrs max.)

 

[BackCountry]

Thanks BackCountry.

No, there is no main breaker in the backed up 125A sub panel.
I will see if that is an option.

(BTW - This older BUI can take only 3@40A brkrs max.)

Cool, then I’d add a main breaker or back feed a 125A breaker if the panel is listed for it

 

[jaggedben]

Thanks BackCountry.

No, there is no main breaker in the backed up 125A sub panel.
I will see if that is an option.

(BTW - This older BUI can take only 3@40A brkrs max.)

I don't see how it's not a code violation if there isn't a breaker protecting the backup panel. 705.12(B)(1). (2020 NEC reference. )

 

[Zee]

In other words it is ALREADY a code violation whether I add more PV or not?
(since the utility OCPD is 110A and there is 40A PV also. The sum of 150A exceeds the (E) feeders and 125A sub panel rating.)

Also, it seems I have the option of rectifying it by
- either increasing the ampacity of both the downstream feeder and sub panel (to 110A utility brkr + 2@40A pv brkrs = 190A)
- or adding a downstream breaker sized such that it protects the feeder and sub panel? (125A)

 

[jaggedben]

Yeah. If you can't put a breaker in the BUI, hopefully you can put a main breaker in the panel.

Not being familiar with the SE BUI, I don't know what their provisions for a backup loads breaker are. In the Enphase Sytem Controller, there's a provision for a backup loads breaker and I almost always use one. The few exceptions were when I had a main breaker in the backup sub right next to it. Actually I think there was also one time I had a 125A backup panel and the grid, pv and battery breakers were 80+20+20, and I used 2awg to the panel.

 

[BackCountry]

Yeah. If you can't put a breaker in the BUI, hopefully you can put a main breaker in the panel.

Not being familiar with the SE BUI, I don't know what their provisions for a backup loads breaker are. In the Enphase Sytem Controller, there's a provision for a backup loads breaker and I almost always use one. The few exceptions were when I had a main breaker in the backup sub right next to it. Actually I think there was also one time I had a 125A backup panel and the grid, pv and battery breakers were 80+20+20, and I used 2awg to the panel.

For Enphase, I almost always put the backup loads and utility breaker in the MSP and backup loads panel just because the Eaton CSR breakers were hard to find and more costly.

The SE BUI has a built in 200A breaker on the utility side (they make two versions, one is service entrance listed). It does not have a load side breaker, so yes you must put a main breaker or 125 OCPD between it and the loads panel. It’s a really simple device and I’m not very fond of it. I’ve installed two of them and don’t really care for how it works or the conduit layout on the bottom of it (think SolArk but worse).

 

[Zee]

Thx!
Yep, no provision for backup loads breaker in BUI.

But backup loads sub panel has a provision for a main breaker.