Another busbar question

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JoeNorm

Senior Member
Location
WA
I came across a situation I haven't seen yet. It's an older meter can with breaker spaces below the meter socket. I am used to seeing a main breaker suppling the bus but there does not appear to be one here(I have only seen a photo).

If that is the case, how do I apply 705.12 rules for the busbar? It talks about two sources of power on opposite ends of the bus, but they only talk about having an OCPD on either end. In this case it looks like I have a main lug supply, a bus, and a PV source on a breaker.

thanks for the thoughts
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Adding a breaker for PV to that bus would be a supply side connection, since it's not on "the load side of the service disconnecting means".

Cheers, Wayne
 

JoeNorm

Senior Member
Location
WA
The busbar is currently feeding 200A to a house, 50A to a guest house, and 50A to a shop.

We would be adding solar to the Shop. I still am confused and see a busbar with two sources of power on either end of it and loads in between. Does the 120% rule still apply?
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
No, the 120% rule does not apply to supply side connections, one of the advantages of them.

That busbar is a service conductor and is currently only protected by the load calculation (assuming a < 300A meter/busbar). Adding a second source of power isn't going to change that situation or make it worse.

Cheers, Wayne
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
The 120% rule is in the section covering connections on the load side of the service disconnecting means. So it doesn't apply to busbars on the supply side. Those are service conductors and no complicated rules apply to them with regarding to solar or other inverter outputs.

Only other thing to be aware of is that the 2020 NEC outlawed those type of service panels (by requiring each service disconnect to be in its own sectioned off space). But if you are backfeeding the shop and not touching the service panel, your AHJ may grandfather that.
 
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