Code reference for grounded conductor - Electrician Talk - Professional Electrical Contractors Forum

subelect · 12-28-2008, 08:26 PM

For my own knowledge, I am trying to get a few code requirements straight.

When we wire up a 440 volt, 3 phase system for a new application (say with 250-250-250-3/0 quad wires) with no neutral load, should the grounded conductor be phase marked white or green at the first connection point? What is the code reference?

Next, at a dwelling's service entrance and the homeowner has us install a connection box (for his small generator to feed his 110 volt gas furnace)to the side of the breaker box, doesn't that still constitute being a part of the service entrance? Can't you connect the neutral and egcs together at that connection box bolted to the side of the breaker box? Since it is physically attached, what part of the NEC says that is not the service entrance?

Thanks.

480sparky · 12-28-2008, 08:42 PM

Grounded conductor is 200.7.
Grounding conductor is 250.119.

InPhase277 · 12-28-2008, 09:15 PM

Quote:

Originally Posted by subelect

For my own knowledge, I am trying to get a few code requirements straight.

When we wire up a 440 volt, 3 phase system for a new application (say with 250-250-250-3/0 quad wires) with no neutral load, should the grounded conductor be phase marked white or green at the first connection point? What is the code reference?

Yes, where the neutral wire is used, it should be identified. Article 200.

Quote:

Next, at a dwelling's service entrance and the homeowner has us install a connection box (for his small generator to feed his 110 volt gas furnace)to the side of the breaker box, doesn't that still constitute being a part of the service entrance? Can't you connect the neutral and egcs together at that connection box bolted to the side of the breaker box? Since it is physically attached, what part of the NEC says that is not the service entrance?

Thanks.

It depends on how the generator's neutral is grounded and how the switching occurs for connection to the generator. This is covered in 250.30, Separately Derived Systems. Basically, if the generator's neutral is NOT bonded to the frame, and the system neutral and generator neutral are solidly connected, it is not considered a separately derived system, and the bond takes place at the Main Bonding Jumper.

If the generator's neutral IS bonded to the frame, and the system neutral and generator neutral are not solidly connected, then it is a separately derived system.

jwelectric · 12-29-2008, 12:24 PM

Quote:

Originally Posted by subelect

Next, at a dwelling's service entrance and the homeowner has us install a connection box (for his small generator to feed his 110 volt gas furnace)to the side of the breaker box, doesn't that still constitute being a part of the service entrance? Can't you connect the neutral and egcs together at that connection box bolted to the side of the breaker box? Since it is physically attached, what part of the NEC says that is not the service entrance?

Thanks.

What kind of box?

What kind of generator?

No it is not part of the service equipment.Atricle 230 will tell you what is part of the service equipment and a box mounted to the side of a panel enclosure is not mentioned in that article therefore it is not part of the service equipment.

Depending on the type of generator and its connection to the building will mandate if a disconnect that is rated as service equipment will be required.