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What does the NEC consider a sub-Panel


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Okay I?ve been down this road before but I can?t find anything in either the NEC, or the ?Electrical Inspection of Existing Dwellings (By Hansen) that gives me a clear definition of when a panel is a sub-panel. I know I?m going to get push back on an issue and I want supporting reference material.

The house was built in 1972 with several additions.

Scenario 1 ? There is a disconnect on the outside of the house next to the meter. Directly on the other side of the wall, inside the garage, there is a panel filled with breakers, but with no single disconnect. Is this a sub-panel requiring the separation of the grounds & neutrals?

Scenario 2 - There is a disconnect on the outside of the house next to the meter. Somewhere in the garage there is a panel filled with breakers and also has a single disconnect (in addition to the disconnect on the outside of the house). Is this a sub-panel requiring the separation of the grounds & neutrals?

Scenario 3 - There is a disconnect on the outside of the house next to the meter. Way way far away on the other side of the house there is a brand new garage. There is a panel with breakers and a single disconnect (in addition to the disconnect on the outside of the house). Is this a sub-panel requiring the separation of the grounds & neutrals?

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You won't find a definition of a sub panel in the NEC because they don't use that term.

The NEC reference you're looking for is 250.142(B).

In Electrical Inspection of Existing Dwellings, check sections 3.7.3 and 4.3.1 for an in-depth discussion and some other NEC references.

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250.24 (A) 1 thru 5 give detail on where the grounded service conductor and electrode grounding conductor can be connected. Basically, it says, among other things, that the grounded service conductor - AKA neutral - cannot be connected to equipment grounding conductors or to equipment enclosures on the load side of the main service disconnect. So, you have to carry your equipment grounding conductor from the line side of the disconnect to the load side with a 4th conductor because you can't use the neutral for that after the main disconnect.

Mains have 3 wires, subs have 4.

Marc

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?250.24 (5) Load-Side Grounding Connections. A grounded conductor shall not be connected to normally non?current-carrying metal parts of equipment, to equipment grounding conductor(s), or be reconnected to ground on the load side of the service disconnecting means except as otherwise permitted in this article.

?250.142 (A) Supply-Side Equipment. A grounded circuit conductor shall be permitted to ground non?current-carrying metal parts of equipment, raceways, and other enclosures at any of the following locations:

(1) On the supply side or within the enclosure of the ac service-disconnecting means

(2) On the supply side or within the enclosure of the main disconnecting means for separate buildings as provided in 250.32(B)

(3) On the supply side or within the enclosure of the main disconnecting means or overcurrent devices of a separately derived system where permitted by 250.30(A)(1)

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?250.142 (A) Supply-Side Equipment. A grounded circuit conductor shall be permitted to ground non?current-carrying metal parts of equipment, raceways, and other enclosures at any of the following locations:

(1) On the supply side or within the enclosure of the ac service-disconnecting means

....

Does this mean that it's ok to ground an AC condenser disconnect enclosure and air handler disconnect enclosure to the neutral but not the condenser unit itself or the air handler itself?

Marc

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?250.142 (A) Supply-Side Equipment. A grounded circuit conductor shall be permitted to ground non?current-carrying metal parts of equipment, raceways, and other enclosures at any of the following locations:

(1) On the supply side or within the enclosure of the ac service-disconnecting means

....

Does this mean that it's ok to ground an AC condenser disconnect enclosure and air handler disconnect enclosure to the neutral but not the condenser unit itself or the air handler itself?

Marc

They mean alternating current not air conditioning. But you knew that didn't you?

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?250.142 (A) Supply-Side Equipment. A grounded circuit conductor shall be permitted to ground non?current-carrying metal parts of equipment, raceways, and other enclosures at any of the following locations:

(1) On the supply side or within the enclosure of the ac service-disconnecting means

....

Does this mean that it's ok to ground an AC condenser disconnect enclosure and air handler disconnect enclosure to the neutral but not the condenser unit itself or the air handler itself?

Marc

They mean alternating current not air conditioning. But you knew that didn't you?

Jeez.[:-paperba

Marc

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Thanks Chad, Jim Marc I appreciate it. It would make life easier if we all used the same language. Reading the code is like translating Japanese sometimes.

It's done for job security.

If everyone understood the rules and why they were written, there'd be no need for enforcers.

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Thanks Chad, Jim Marc I appreciate it. It would make life easier if we all used the same language. Reading the code is like translating Japanese sometimes.

It's done for job security.

If everyone understood the rules and why they were written, there'd be no need for enforcers.

OK ... you guys set this up all by yourselves ... and I can't resist!!

+++++

And then you add in the dialects from a Canadian and someone from Louisiana you really have some potato and ham soup or gumbo.

+++++

[;)][;)]

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