IWire, I read the Automatic Transfer Switch - Art 702 link you noted with great interest... thanks. Looks like seems we think alike... wow... if you were a girl I'd marry you, LOL!

It looks like we're fighting a losing battle though; the duties the NEC is charged with is growing increasingly corrupted by manufacturers. Generators are protected and the associated wiring is protected not only by internal electronics (which are very sensitive) but by an OPCD. As was poined out in the thread, if you've got 40 20A breakers, do you need 800A service? And how many times are POCO service feeders sized way to small if they had to follow code? So if there service doesn't have to be upgraded, why should the genset?

Larry Fine makes a good point in that thread of using the aux contacts for load shedding (mine has them) but will that be enough to satisfy an AHJ under the proposed rules?

I do have a problem with the this part of the 702.5 Capacity and Rating for 2008:

(B) System Capacity. The calculations of load on the standby source shall be made in accordance with Article 220 of by another method that is acceptable to the authority having jurisdiction.

It the "another method that is acceptable to the authority having jurisdiction" I have a problem with. I can just see how that will go with the "right" types... though some AHJ's don't seem to give a hoot how or even if a genny is installed. My system passed without the genny in place! AHJ and POCO couldn't care less about what kind of generator I was using... they just wanted to see if the wiring was done to code, no interconnection, proper grounding and bonding, and gas piping was correct and holding 5 PSI when they got there. POCO even said we don't check "appliances". I've seen this on other jobs too - except for some reason when diesel is involved.

It should be pointed out that a genset with a dedicated panel can be overloaded just the same. A 10 Kw genset hooked up to an 8 breaker panel, with 5 15A and 3 20A breakers has a total load potential of 135A. Generator only produces 41.66A so we're in the same boat again. That genset can be overloaded.

As Reno pointed out, it's no good to have a massively oversized genset either. And what about physical space, there might not be enough room for such an oversized unit, not to mention the gas requirements of having such a huge genset. What if the POCO won't upgrade your gas service enough to feed an oversized beast (a 45Kw unit will burn over 500,000 BTU on average), then what happens?

Regarding disconnects really doesn't make a differnce in my opinion... you've got one of the best ones of all - the gas (or fuel) valve - turn it off and the genset stops producing power instantly. Fire department would probably do that anyway in an emergency.

Joe