100% Backup Generator - Disconnecting Means

[charlie b]

I was reminded this morning by the following quote that I wanted to post a question of my own.

. . . the transfer switch is service rated with a disconnecting means. GEC is relocated to the ATS.

It came from this thread:
http://forums.mikeholt.com/showthread.php?t=147660

I have a similar situation, one in which the owner wants a generator to supply the entire load of the building. It is not a dwelling unit, and the system will fall under 702 (optional standby). Can I bring both the utility service and the generator output directly to the ATS, and let the ATS serve as the building?s required disconnecting means?

From the comment I quoted above, I infer that I can specify an ATS that has the appropriate listing. I also infer that a "service-rated ATS" would have a method of bonding Neutral to Ground, a place to connect the GEC, and a method of providing separate N and G conductors downstream from that point. But how does it function as a disconnecting means? Does the ATS simply need a mid-position for OFF (and be lockable in that position)? Is there a separate breaker downstream of the transfer portion of the device, but within the same enclosure, so that that constitutes the building?s disconnecting means?

 

[augie47]

I have seen service rated ATS units with a service disconnect and a generator disconnecting and I have also seen units with only a service disconnect means.
In the case where there is only a service disconnect means, my opinion would be that you need to meet 225.32-36 with 702.11 in mind ('08 Code references) for the generator.

 

[hillbilly1]

I have installed lots of those, the Blue box uses those on retrofits. The transferswitch is service rated and uses motorized breakers. (actually one motorized breaker for the utility side, and one motorized molded case switch for the generator side) It has a key switch that can be turned to make the switch "Go to neutral". If the utility breaker trips, it will lock itself out from transferring so it does not transfer into a fault.