310.12(B)

Does 310.12(B) apply to the scenario?

  • 310.12(B) would still apply.

  • 310.12(B) would no longer apply, and the feeder would need to be increased in size to meet 310.16.

  • 240.4(B) would apply

Results are only viewable after voting.
Status
Not open for further replies.
C

cherriott

Member
Location
Georgia
Occupation
Inspector/Plans Examiner
A single family dwelling has a 200 ampere Meter/Disconnect combo with 12 space panel (see Eaton model CMB1212B200BTS for an example) with feed-through lugs. A 4/0 Aluminum feeder cable is installed between this equipment and the branch circuit panelboard located inside the home. Up to this point, I believe 2020 NEC §310.12(B) would apply.

Scenario: The HVAC Condensing unit sits 3' to the right of the meter/disconnect. Rather that pulling the branch circuit from the interior panel, they decide to pull power from 2 of the available 12 spaces in the meter/disconnect combo. Would 310.12(B) still apply to the feeder supplying the branch panelboard even though the feeder no longer supplies the "entire load" associated with the dwelling?

The answers in the poll are actual answers I have received from electricians and electrical inspectors. Once we all agree on an answer, I'll throw another curveball your way.
 
First of all, my '17 NEC has no 310.12, but I'm inferring the topic by the question.

It still applies because a feeder need not be larger than the service conductors.
 
LarryFine said:
First of all, my '17 NEC has no 312, but I'm inferring the topic by the question.

It still applies because a feeder need not be larger than the service conductor
Click to expand...
This post references the 2020 code. 2017 would be 310.15(B)(7). What is your code reference for your answer? In this case, there really isn't any "service conductors" because the conductors supplying the meter center are supplied and installed by the serving utility, making the service point on the load side of the meter. The service disconnect is directly connected to the bus bar on the load side of the meter, therefor no "service conductors" are present (speaking hypothetically.)

Make sure you vote as well.
 
Last edited:
infinity said:
#4/0 Al is rated for 180 amps. Next size up rule would allow a 200 amp OCPD.
Click to expand...
This here. As long as the calculated load is 180 or less it really doesn't matter if you can apply 310.12(B) because 4/0 aluminum is acceptable here anyway.
 
I feel like we can all agree that 240.4(B) would apply in this situation. The feeder conductors when supplying the entire load associated would need to be rated for 166 amperes. If the feeder doesn't supply the entire load, then it would need to meet 240.4(B).

This seems to trip a lot of people up, and I can see why. You would think that the feeder/service conductor would need to be rated for more when supplying the entire load.

See my next post in this forum for the curveball.
 
cherriott said:
This post references the 2020 code. 2017 would be 310.15(B)(7). What is your code reference for your answer? In this case, there really isn't any "service conductors" because the conductors supplying the meter center are supplied and installed by the serving utility, making the service point on the load side of the meter. The service disconnect is directly connected to the bus bar on the load side of the meter, therefor no "service conductors" are present (speaking hypothetically.)

Make sure you vote as well.
Click to expand...
The application of 310.12(C) does not require that there be "service conductors installed".
And I have no interest in voting on things like this...I see polls as a waste of time and having ZERO value to the members of this forum.
 
don_resqcapt19 said:
The application of 310.12(C) does not require that there be "service conductors installed".
And I have no interest in voting on things like this...I see polls as a waste of time and having ZERO value to the members of this forum.
Click to expand...
Then remove the capability?
 
cherriott said:
This post references the 2020 code. 2017 would be 310.15(B)(7). What is your code reference for your answer? In this case, there really isn't any "service conductors" because the conductors supplying the meter center are supplied and installed by the serving utility, making the service point on the load side of the meter. The service disconnect is directly connected to the bus bar on the load side of the meter, therefor no "service conductors" are present (speaking hypothetically.)

Make sure you vote as well.
Click to expand...
I voted first.

What I referred to mentions calculated sizing, not actual wires, so it still applies.
 
Status
Not open for further replies.
Top