A question for load side connection 705.12(B)

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fandi

Senior Member
Location
Los Angeles
diagram.png

Hi All,
The design is only for NEC 2017 and not NEC 2020. The 100A bus MSP only has a main and a PV breaker.
To me, the diagram would meet 705.12(B)(2)(3)(c) but my co-worker said that section does not apply to the design because there are no loads at the MSP. The language of the code section c) is '...both load and supply devices, ...' .
He also said 705.12(B) does not apply to the design because the MSP is not capable of supplying multiple branch circuits or feeders, or both because to him, there are no circuit breakers at this MSP other than the 100A main breaker and the 100A power production source breaker.
So my question is not about whether the diagram meets the code but is my co-worker right about two underlined things he said.

Thank you.
 

packersparky

Senior Member
Location
Wisconsin
Occupation
Inspector
I believe it could be compliant with 705.12(B)(2)(3)(c).

(c) The sum of the ampere ratings of all overcurrent devices on panelboards, both load and supply devices, excluding the rating of the overcurrent device protecting the busbar, shall not exceed the ampacity of the busbar. The rating of the overcurrent device protecting the busbar shall not exceed the rating of the busbar. Permanent warning labels shall be applied to distribution equipment displaying the following or equivalent wording:
WARNING:
THIS EQUIPMENT FED BY MULTIPLE SOURCES. TOTAL RATING OF ALL OVERCURRENT DEVICES EXCLUDING MAIN SUPPLY OVERCURRENT DEVICE SHALL NOT EXCEED AMPACITY OF BUSBAR.

The warning sign(s) or label(s) shall comply with 110.21(B).
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
...
So my question is not about whether the diagram meets the code but is my co-worker right about two underlined things he said.

Thank you.
Your co-worker's arguments are all wrong.

The 100A breaker to the gateway serves both loads and supplies, and even if it only served one of those it would still count toward 705.12(B)(2)(3)(c).
'Capable' does not mean that multiple feeders and branch circuits have to be presently installed.
 

packersparky

Senior Member
Location
Wisconsin
Occupation
Inspector
Your co-worker's arguments are all wrong.

The 100A breaker to the gateway serves both loads and supplies, and even if it only served one of those it would still count toward 705.12(B)(2)(3)(c).
'Capable' does not mean that multiple feeders and branch circuits have to be presently installed.

Isn't the MSP panel compliant though as long as it doesn't supply any other loads? I don't believe he was asking about the gateway.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Isn't the MSP panel compliant though as long as it doesn't supply any other loads? I don't believe he was asking about the gateway.
Yes the install is compliant. But that wasn't his question. (Note the part of his post I quoted.)

The install happens to be compliant, but not for the reasons his co-worker is giving.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
The OP has no details on the MSP. But say it is a main breaker 4 position panel, where none of the positions accept tandem breakers. Then I think the second argument in reference to the second sentence of (2017) 705.12(B) has merit (if not for the reasons cited, which have to do with what is installed, rather than what is installable.)

That sentence starts off "Where distribution equipment, including switchgear, switchboards, or panelboards, is fed simultaneously by a primary source(s) of electricity and one or more other power source(s), and where this distribution equipment is capable of supplying multiple branch circuits or feeders, or both . . ."

Seems to me that sentence implies at least 4 separate connections (per pole) to the busbar, 2 for the two separate "feeds" from the multiple power sources, and 2 for the multiple branch circuits or feeders. So if the equipment is limited to 3 connections (per pole), it would not meet that predicate.

Is this how the quoted text is commonly understood?

Cheers, Wayne
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Technically you are correct Wayne, but in the real world such a panel would be practically non-existent. I can only think of one panel I've ever seen that could be set up that way, and I've never seen it set up that way.

Also your number of connections doesn't necessarily have to be directly to the busbar, since a quad or tandem breaker supports up to 2 circuits per each connection to the busbar.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Technically you are correct Wayne, but in the real world such a panel would be practically non-existent.
Thanks for the agreement and the reality check.

Also your number of connections doesn't necessarily have to be directly to the busbar, since a quad or tandem breaker supports up to 2 circuits per each connection to the busbar.
Yes, that's why I was careful to specify the hypothetical panel wouldn't accept tandems. : -)

Cheers, Wayne
 
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