240V Single -Phase Power Feed

[FountainGuy]

I have an EE that is specifying (3) #3/0 + #6G for a 200A power feed to a non-residential site. Shouldn't it be just (3) #3/0 (two hot and a ground), just like for power to a house?

The only unique thing about this power feed is that the power is going from the meter and disconnect to an ATS first (ASCO model ATS-G-1PH-11BE-3R), then to the load center. I know that you can order the ATS with an optional full rated neutral configuration, but is the neutral lug on the ATS not necessary for this feed as the main panel accepts just two hot and a ground?

 

[augie47]

Assuming your disconnect at the meter has OCP then this would be a feeder. If there is no neutral load then the equipment ground is all you need past your service disconnect. That said, I would be surprised if the ATS or generator did not have a neutral load.

 

[infinity]

I have an EE that is specifying (3) #3/0 + #6G for a 200A power feed to a non-residential site. Shouldn't it be just (3) #3/0 (two hot and a ground), just like for power to a house?

The only unique thing about this power feed is that the power is going from the meter and disconnect to an ATS first (ASCO model ATS-G-1PH-11BE-3R), then to the load center. I know that you can order the ATS with an optional full rated neutral configuration, but is the neutral lug on the ATS not necessary for this feed as the main panel accepts just two hot and a ground?

Is this the service disconnect? If so you need a separate EGC run with the feeder to the panel. So you what then EE specified seems correct.

 

[FountainGuy]

Yes. Power on site originates from 240V 1-PH meter, then to service disconnect, then to ATS, then to breaker panel (normal) and to diesel generator (emergency power).

 

[infinity]

Yes. Power on site originates from 240V 1-PH meter, then to service disconnect, then to ATS, then to breaker panel (normal) and to diesel generator (emergency power).

Thanks for clarifying that. Once you go past the service disconnect you need an EGC in each feeder but unless the transfer switch or panel require a neutral you do not need to install one.

 

[FountainGuy]

And the EGC for a 200A feed should be the same size as the 240V conductors, 3/0 in this case, correct? I had another site in which (2) #3/0 + #6G was specified for the feed and the county said that it had to be (3) #3/0 per 2017 NEC 250.24(c).

 

[infinity]

And the EGC for a 200A feed should be the same size as the 240V conductors, 3/0 in this case, correct? I had another site in which (2) #3/0 + #6G was specified for the feed and the county said that it had to be (3) #3/0 per 2017 NEC 250.24(c).

No, for the feeders EGC it can be sized according to T250.122 which would be #6 for 200 amps. Once you're beyond the service disconnect 250.24(C) has nothing to do with it.

 

[Ingenieur]

so no 120 vac loads?

 

[FountainGuy]

so no 120 vac loads?

Yes, there are several 120V loads in the load center. I'm just concerned about conductor sizes and quantity between the existing disconnect and the ATS, and then from the ATS to the load center and to the generator. I believe that (3) #3/0 + #6G is correct as the EE specified.

I originally thought that it would be (3) #3/0 to the load center and that the third conductor is ground and the neutral doesn't become a neutral until the ground wire reaches the main load center. I don't have but two hot and a ground coming to my load center at my house and the neutrals and ground wires are on the same bus. My house has the main on the load center, which makes this conductor quantity/size different.

 

[infinity]

A 200 amp, single phase, 120/240 volt feeder with 3-#3/0 and 1-#6 EGC is an extremely common installation.

In your house your SEC's are 3 conductors, H-H-N, not H-H-EGC on the line side of the service disconnect.

 

[Strathead]

Yes, there are several 120V loads in the load center. I'm just concerned about conductor sizes and quantity between the existing disconnect and the ATS, and then from the ATS to the load center and to the generator. I believe that (3) #3/0 + #6G is correct as the EE specified.

I originally thought that it would be (3) #3/0 to the load center and that the third conductor is ground and the neutral doesn't become a neutral until the ground wire reaches the main load center. I don't have but two hot and a ground coming to my load center at my house and the neutrals and ground wires are on the same bus. My house has the main on the load center, which makes this conductor quantity/size different.

You have, at a minimum a problem with semantics, and I tend to believe that leads to or originates with a failure to understand so let me try to clarify a little.


neutral carries the unbalanced current between hot conductors
grounded conductor is a conductor intended to carry current that is intentionally in contact with earth or ground
grounding conductor is a non-current carrying conductor that ties non-current carrying conductive parts together and to earth, or the grounded conductor or both.
ground is earth.

Also, please read the definitions in the front of the code book, for more clarification.

So, the service coming in to your house contains two hots and a neutral (definitely not ground or a grounding conductor). Once it leaves the first means of disconnect there are two hots, the grounded conductor (which is also the neutral) and a grounding conductor. We, in the industry often use the word(s) ground and ground wire, but the code doesn't, and when someone is trying to grasp the concepts, the use of "ground" can get in the way of understanding.

Hope this helps.

 

[FountainGuy]

Thanks, Strathead. What threw me off is that the neutral (carries the unbalanced current between hot conductors) that enters the house alongside the two hots is typically a bare stranded aluminum conductor.

 

[kwired]

Thanks, Strathead. What threw me off is that the neutral (carries the unbalanced current between hot conductors) that enters the house alongside the two hots is typically a bare stranded aluminum conductor.

It can be bare if on the supply side of the service disconnect. There is no separation of grounded/equipment grounding conductors on the supply side of service disconnect - just one grounded conductor that does bond to any metallic enclosures.

 

[Strathead]

Thanks, Strathead. What threw me off is that the neutral (carries the unbalanced current between hot conductors) that enters the house alongside the two hots is typically a bare stranded aluminum conductor.

The other conductors are generally aluminum in this situation also. This is for overhead. When run underground the neutral is and insulated conductor wright along with the hots. The code just allows but doesn't require the neutral to be bare because it is grounded at the utility transformer and therefor deemed safe.