Backfeeding into a service panel with no main breaker

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Leviathan

Member
Location
Arizona
Occupation
Solar Operations
Hello all,
I'm considerably new to PV design and I have a bit of confusion as to my options with interconnecting into a main service panel with no main breaker. NEC 2017, Arizona, SRP Utility.
Lineside taps are a bit of a pain in the ass with SRP. I know that I can install a new service panel or subpanel with a main breaker. Are there any better solutions? I was under the impression that I could backfeed directly into a hot bus if I included a fused disconnect in the design, but this may be incorrect. Any information or suggestions would be helpful. Thanks in advance.
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Personally I think it's an ideal situation if the existing breakers are less than 6. Just add the PV as the 6th. Utility should have no say in the matter if the building department approves. In my opinion of course. Your milage may vary. And then there's the 2020 NEC which prohibits those panels, not something I've had to deal with yet.
 
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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
jaggedben said:
Personally I think it's an ideal situation if the existing breakers are less than 6. Just add the PV as the 6th. Utility should have no say in the matter if the building department approves. In my opinion of course. Your milage may vary. And then there's the 2020 NEC which prohibits those panels, not something I've had to deal with yet.
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A backfed PV breaker should not count as a 7th handle. I fought that battle and won it here in Austin with some help from an excerpt from a Mike Holt training video.
 
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Leviathan

Member
Location
Arizona
Occupation
Solar Operations
For a little more context, here is the panel in question. I'm really trying to avoid an MPU for this and for similar situations in the future.
NgmEndspBqFv.jpg
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Yup, that's a code violation unless there's a disconnect and overcurrent device upsteam. Either find those things, install them, or replace that panel.
 
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jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
That's a bit of a crazy situation, but it appears you may have a compliant panel (pre-2020 NEC) with 6 service disconnecting breakers at top. And you may be able to legitimately backfeed either bus. On the lower bus it depends on the bus rating and your backfeed size. That label seems to show that tandems are listed to go on the lower bus, which you'd need to do to make space.

I've never actually backfed a panel like this, mind you.

EDIT: The two single pole breakers on the 9 and 11 positions appear to give you 7 handles and would need to be moved to be pre 2020 NEC compliant.
 
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inforaj

Member
Location
Chiago
Occupation
Member
mdOPSP said:
Hello all,
I'm considerably new to PV design and I have a bit of confusion as to my options with interconnecting into a main service panel with no main breaker. NEC 2017, Arizona, SRP Utility.
Lineside taps are a bit of a pain in the ass with SRP. I know that I can install a new service panel or subpanel with a main breaker. Are there any better solutions? I was under the impression that I could backfeed directly into a hot bus if I included a fused disconnect in the design, but this may be incorrect. Any information or suggestions would be helpful. Thanks in advance.
Click to expand...
For the safe side, in some of the projects, I have used the current limiting device that will control the back-feeding currents when the PV system connects to the secondary side of load sections.
 
L

Leviathan

Member
Location
Arizona
Occupation
Solar Operations
inforaj said:
For the safe side, in some of the projects, I have used the current limiting device that will control the back-feeding currents when the PV system connects to the secondary side of load sections.
Click to expand...
Forgive me for being naive, but what sort of device?
 
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PWDickerson

Senior Member
Location
Clinton, WA
Occupation
Solar Contractor
This panel is just asking for an upgrade, and someone would have to do a fair amount of work to address the code violations, but one could certainly install a a decent amount of solar in it if needed. The limitation would be the current limit of the breaker stabs, which are probably 125A. Move the 1P breakers in positions 9 and 11 to the lower section (will require installing mini's), and install the solar backfeed breaker in those freed-up spaces in the upper section. Since there is no OCPD ahead of the multiple service disconnects (solar breaker included), this would be considered a line-side connected system limited in size by the rating of the service equipment. The breaker stabs will be the choke point. This type of installation is allowed in my jurisdiction, but I know that others do not allow it, so check with your AHJ.

Better yet, upgrade that 60 year old panel! Unlike French wines, electrical equipment doesn't improve with age!
 
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