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Kyle_in_rure
Dec 26, 2012, 04:23 PM
Hello,
I installed a generator interlock kit on my main panel to use with my Coleman 5000 watt generator during long power outages. I hooked it up and tested it and all was successful. However, One concern I have is with the lack of switching with the neutral; the neutral bus will still be connected to the utility even when I use the generator. I'm assuming that all is well because there will be no load being used from utility power, only from the generator, but all of this is a little over my head. I have a couple of questions:
Are there any potential problems that arise with this situation? I do know the neutral and grounds are NOT bonded in my generator, if that affects anything.
Would there be a significant danger in this regard if they were bonded? (besides current flowing on both neutral and ground conductors between generator and panel)
Thanks.

mike 165278
Dec 26, 2012, 06:49 PM
The neutral does not need to be broken. The generator frame should be grounded, and the neutral should remain unbonded.

hfcarson
Dec 27, 2012, 06:05 AM
Kyle...
As long as your transfer switch isolates and/or disconnects all the phase conductors from the utility, a solid neutral in the transfer switch should not cause you any issues...
Whether the generator is internally neutral to ground bonded (which is common on smaller units) or not should not be an issue. Being sure you have an established neutral to ground bond at your main panel that remains, regardless of the utility or generator connection is important.
f.y.I. NEC 700.5 in the Handbook discusses the transfer switch connections and some of the bonding issues in some depth...

tkrussell
Dec 27, 2012, 07:45 AM
Hrcarson,

Article 700 is for Emergency Systems. Only.

ARTICLE 702 Optional Standby Systems applies to residential systems.

Article 250 handles grounding and bonding.

hfcarson
Dec 27, 2012, 08:27 AM
Yes Sir, Article 700 is for Emergency Systems although regarding the grounding and bonding, this issue is referred to again in 701.5, 701.7, 702.5 and 702.7...
"See the commentary..."
Kyle's question included the issue of the grounding and bonding of generator or lack of, along with the neutral connections to the normal. The commentary of 700.5 in the handbook talks about the solid neutrals in transfer switches as required by 250.24 and the corrective actions available (250.6(B)) when multiple grounding creates objectionable currents. I believe this is general information that can be applied to emergency, standby and optional systems.
I had only intended on providing this for informational purposes...

Kyle_in_rure
Dec 27, 2012, 09:26 AM
So basically it is dependent upon a solid neutral/ground bond as well as a solid ground connection at the main panel.

Thanks for the answers.

tkrussell
Dec 27, 2012, 10:38 AM
Correct. Only if a system is considered as a separately derived system, which yours is not, N/B connections at all distribution points.