Omit neutral from run to Outside Disconnect

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solarken

NABCEP PVIP
Location
Hudson, OH, USA
Occupation
Solar Design and Installation Professional
I have been running into this a lot lately. With Inverter, transfer switch, and main service panel installed indoors, typically in a basement area, I usually install a wiring trough below the equipment to simplify the paths between components and keep it neat and organized. But typically the utility still wants an outside accessible solar disconnect. To accomodate the utility and to serve as the Rapid shutdown switch, I like to install a lockable disconnect outside, and just run a single conduit through the wall from the wiring trough. The only conductors needed in the switch are the L1 and L2 conductors, and an EGC. I understand 300.3(B) specifies 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, etc. However, the Neutral is not used in the outside disconnect, and the disconnect only serves to de-energize the L1 and L2 conductors. Running the neutral out from the gutter in the conduit with the L1 and L2 and switched L1 and L2 conductors out to the switch and back serves no purpose. I cannot think of an issue with OCPD with this arrangement either. If there were a Ground fault on L1 or L2 in the path, the OCPD protecting the path would trip, with the fault current returning through the bonding jumper at the service. If there were a Line to line fault, ditto. I appreciate any thoughts or opinions on this situation.
 
petersonra said:
note the use of the words "where used" with respect to the grounded conductor.
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Thanks for reply. Yes, that is what I was referring to. Neutral is not used in the disconnect. It is used in the inverter and in the transfer switch. So I believe I should be able to leave it out of the conduit to the switch, while still running it with the phase wiring between the inverter and the transfer switch point of connection. Just trying to confirm others interpret similarly.
 
See also 300.20.

The key here is that all current that might be carried on conductors in the conduit is returned on conductors in the same conduit. So you have L1 going and returning, and L2 going and returning, so you're okay.

I've dealt with more than one inspector who didn't understand this. Just a heads up.
 
jaggedben said:
See also 300.20.

The key here is that all current that might be carried on conductors in the conduit is returned on conductors in the same conduit. So you have L1 going and returning, and L2 going and returning, so you're okay.

I've dealt with more than one inspector who didn't understand this. Just a heads up.
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What about current on the neutral caused by imbalanced 120V loads?
 
ggunn said:
What about current on the neutral caused by imbalanced 120V loads?
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There is none present if the neutral does not connect to the equipment. If you bring the neutral to the switch and back out in the same conduit, then the neutral currents cancel each other out, too. Makes no difference.
 
jaggedben said:
There is none present if the neutral does not connect to the equipment. If you bring the neutral to the switch and back out in the same conduit, then the neutral currents cancel each other out, too. Makes no difference.
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Exactly, in the simplest case, if I brought the neutral from the gutter out to the switch and back to the gutter, it would just be a long loop of wire that serves no purpose.
 
It seems to me a neutral would only be needed if this was a service disconnect where a grounded conductor must be terminated. Even if so, a single conductor should suffice. Otherwise, just an EGC would be needed.
 
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