PV Feed through in sub panel

Merry Christmas

steve burke

Member
Hello Gentlemen,
This is a code question about running PV conductors continuously through, but not connecting to, a sub panel.

the setup..
Have a 200A westinghouse main that i would like to feed 15a (12a from collectors) of solar from a detached garage. Also have 25A breaker at bottom of main panel on house receiving 20a of house solar.

Plan to keep existing 100A subpanel in garage—linked to house main panel with 60 feet of 1-1/4 PVC under driveway and protected by 60amp breaker in main panel. This will service 50A EV charger (3 #3).

In order to get PV from garage roof to main, we need to run pv conductors from garage roof, through garage subpanel and share the conduit with the three #3s providing power to garage.

To keep with the 120% rule for main panel, plan to run two #10s from garage to bottom of main panel while keeping existing #3s (from main to garage) to power car charger.

The question is whether the solar conductors from the garage must be unboken from the garage roof, through the garage sub, and into the house main, of if we can make a connection inside the subpanel transitioning from Romex to THHN.

Ideally, we will run 10/2 romex from garage solar connection and into the sub, then go to individual #10 conductors at sub (without going through a sub breaker), through conduit and into the main panel.
thank you.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
If the garage subpanel is supplied by a 100A breaker in the service panel, and if that breaker is at the opposite end of the bus from the service (next to the 25A breaker for the existing PV), then it would be allowed and much simpler to just terminate the new inverter output conductors in the garage subpanel on a 15A breaker, again at the opposite end of the bus from feeder connection. Or if the 100A breaker in the main panel is not at the opposite end of the bus, to move the 100A breaker.

Cheers, Wayne
 

steve burke

Member
If the garage subpanel is supplied by a 100A breaker in the service panel, and if that breaker is at the opposite end of the bus from the service (next to the 25A breaker for the existing PV), then it would be allowed and much simpler to just terminate the new inverter output conductors in the garage subpanel on a 15A breaker, again at the opposite end of the bus from feeder connection. Or if the 100A breaker in the main panel is not at the opposite end of the bus, to move the 100A breaker.

Cheers, Wayne
Thank you Wayne,
In wiring pv to garage sub (bottom), and using 100A disconnect at bottom of main is far simpler. That said, are you sure that I will not run afoul of 120% rule?
I was concerned that a 100A breaker at bottom of main (although only backfed with 12 amps of solar from garage sub) would be problematic. Thanks again.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
The 120% rule looks at 125% of all the inverter output currents flowing through each bus (along with the opposite end of the bus requirement). So the 100A subpanel can take 16A; 12A < 16A. The 200A main panel can take 32A; 20A + 12A = 32A.

Cheers, Wayne
 

steve burke

Member
The 120% rule looks at 125% of all the inverter output currents flowing through each bus (along with the opposite end of the bus requirement). So the 100A subpanel can take 16A; 12A < 16A. The 200A main panel can take 32A; 20A + 12A = 32A.

Cheers, Wayne
Thanks Wayne. We will proceed with the 25A breaker (20A PV from main house) and 100a breaker (12A from garage PV) both at bottom of main panel. This saves a bunch of cost & work.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
Thanks Wayne. We will proceed with the 25A breaker (20A PV from main house) and 100a breaker (12A from garage PV) both at bottom of main panel. This saves a bunch of cost & work.
You didn't mention before that you already have PV on the house. At the main 200A/200A panel you can connect a total maximum of 32A of PV Imax. It looks like you are just barely compliant.
 
Top