Adding a new Subpanel

Joined
Aug 30, 2004
Messages
28,656
Location
CA
Follow-up to this thread: https://bobistheoilguy.com/forums/t...-electrical-service-from-100a-to-200a.319253/

My house has a "main disconnect" next to the electric meter. Multiple electricians have inspected this "situation" and think I already have 200A service, but am simply out of space. In this "main disconnect" panel, there is a 100A breaker plus a 50A breaker for my A/C unit.
299794463_467472348292234_4682084432409946486_n.jpg

298951567_1143609189524319_5173332517958573970_n.jpg


The 100A breaker leads to a 100A subpanel that is located in an utility room (which is adjacent to the garage). As you can see from these photos, this subpanel is very full.
298806131_548353090305637_5334491377646693484_n.jpg

299650974_1006144273415196_3007783736638718576_n.jpg


I would like to add a second 100A subpanel (in the garage). Obviously the goal is to add capacity for future needs. It has been suggested that I relocate the 50A A/C breaker to this new panel. Based on these photos, does this appear feasible?
 
Joined
Jul 29, 2022
Messages
126
Location
Arizona
As long as the utility confirms the feeder is capable of 200A and the service entrance is rated adequately you should be good.

Meter from PG&E is already rated for 200A. My biggest concern would be that the service entrance does not have enough space (and potential bus bar rating) for you to add another 100A breaker for the subpanel assuming you still have the 30A PV inverter setup. Not sure if you planned on moving both the PV & HVAC to the subpanel.
 
Last edited:
Joined
Sep 30, 2013
Messages
15,275
Location
Indiana
Short answer, yes.

Around here at least, pretty much everything built within the last 30 years or so from the utility to the house is suitable for 200 amps regardless of the house having a 100amp or 200 amp service. You would want to talk to your service provider about that though.

Either way, I don’t see an issue with you adding another sub panel. Simply having the panel will not create any extra loads or create problems.

At the end of the day, you’ll still be fused at 100 amp breaker at the disconnect as well as the 100 amp feeding your new sub.

Remember to separate your grounds and neutrals on the new sub as well as remove the green bonding screw. This should have been done on your “main” as well since it is technically a sub off of your disconnect.
 

The Critic

Thread starter
Joined
Aug 30, 2004
Messages
28,656
Location
CA
299859220_573777731123780_8397451061267384306_n.jpg

298060933_1139036863691212_7172044991042962446_n.jpg


Plot twist: apparently there is an "intermediary" between the main disconnect and the utility room's subpanel.
 

The Critic

Thread starter
Joined
Aug 30, 2004
Messages
28,656
Location
CA
What a mess. I’m having a hard time following the photo.
No dispute.

Here's what I realized: there is a 30A breaker backfeeding into the meter/main combo panel for solar system #1. There is a 35A breaker backfeeding into that weird "intermediary" for Solar system #2. In total, isn't that 65A being backfed into a 100A main breaker?

I thought NEC rules limited the backfeeds to 120% of the bus rating.....which is at most, 40A for a 200A box?
 

The Critic

Thread starter
Joined
Aug 30, 2004
Messages
28,656
Location
CA
Upon further inspection, it appears that I do have 200A electric service at my house. Although the label was gone from my panel, I found a similar house in the neighborhood and a nice neighbor who allowed me to look inside their panel.

1661559983537.png


I was also able to verify that the incoming lines are appropriately sized for 200A service.
1661560030185.png

So, I think the game plan is to:

Add a new 125A subpanel to the garage.
Move the A/C unit's breaker to this new panel, but downsize to 40A (from 50A). AC unit mfg confirmed that 40A is sufficient for my model.
Move the 30A Solar Backfeed for Solar System #1 to this new panel
Run a 20A outlet from this new panel for my air compressor
Add a 60A breaker to this panel and run some 6AWG to an enclosed box for a TBD future EV charger
 
Top