ATS and Conductors

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RAYMFL

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If running conduit from a service to an ATS and a second conduit from the ATS back to the service to feed an existing sub panel, do all the conductors have to be run in both conduits? Can the neutral be omitted from the return conduit from the ATS since it is already terminated at the service panel?

Ray
 
If the grounded conductor is not needed in the transfer switch, then it's nothing more than a 1 phase or 3 phase circuit w/o a grounded conductor running out and back.
Rick
 
buckofdurham said:
If the ats is part of the service then you would use the neutral to ground the can.
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It sounds like the ats and the sub panel is fed from the service panel.
 
chris kennedy said:
Isn't this where we argue 300.3(B)?
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Mabe

My question is, if 300.3(B) must reign, what is the logic behind it?

The service has a 150A MCB with feed-through lugs. Feed to sub panel at house enters at the service panel. Connected to a residential service (to answer previous questions).

Ray
 
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RAYMFL said:
Mabe

The service has a 150A MCB with feed-through lugs. Feed to sub panel at house enters at the service panel (to answer previous questions).

Ray
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Are you feeding the ats via the feed thru lugs w/o ocp?. This would require a main breaker and also the grounded conductor.
 
chris kennedy said:
Isn't this where we argue 300.3(B)?
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Chris, what would be different than a standard single phase or three phase circuit without a grounded conductor.
Rick
 
RUWired said:
Chris, what would be different than a standard single phase or three phase circuit without a grounded conductor.
Rick
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I think nothing. OP has stated that there is an OCPD ahead of the ATS. This is a feeder and I see nothing in 215 that requires the grounded conductor to enter the ATS.

I'm not a fan of 300.3(B). The NEC defines branch circuit, multi wire branch circuit, feeder, service ect. It does not define circuit. That could be anything that supplies power.

300.3(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
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As far as I'm concerned, if the grounded conductor does not serve the AST ( for monitoring or control) then why spend money and take up space.

Sorry I brought it up Rick, but I'll bet this will be discussed further.
 
Yes, you would have to run the grounded conductor in both conduits. The one returning should NOT be connected to the same bar at the service. Instead it should be isolated and travel through to the sub-panel. As Chris pointed out, 300.3(B) would apply.
 
How about 250.24(A)(5). Since these raceways and conductors feed an ATS and then return to feed a sub panel, wouldn't the grounded conductor have to be removed from the bonded neutral at the service disconnect anyway. That would require the grounded conductor be run in the second conduit.
 
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RAYMFL said:
If running conduit from a service to an ATS and a second conduit from the ATS back to the service to feed an existing sub panel, do all the conductors have to be run in both conduits? Can the neutral be omitted from the return conduit from the ATS since it is already terminated at the service panel?
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Yes, the neutral absolutely must be run through the two conduits and the ATS, precisely because there are two conduits. This is no different than the neutral of a 3-wire circuit supplied from a 2-pole GFCi breaker.

If one conduit was used for both directions of the run, the neutral would not be necessary. Then it would be similar to a neutral not being necessary to accompany a 2-wire switch loop.


Added: Paul groks.
 
Thanks for all the input. Felt it necessary to able to give a reasonable explanation to the contractor and this helped me think it through.

Ray
 
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