Grid Tie 240 VAC w/ transfer switch? [RE-wrenches]

[Bob-O Schultze, Electron Connection]

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Chris,
ASSUMING (because you don't say) that your customer wants a manual 
switch (else how would he know he had an outage and to "power down"?) 
and that he has a 200A service, you could put in a manual 200A DPDT 
or 3PDT switch. Two cautions. One, they are a big mother, far bigger 
than a separate service panel, so what's the point? Two, you'll have 
to have the utility power the house down or work getting the feeders 
into the switch hot. Doable, but a little scary. Feeding a dual 60A 
CB and can from the utility side of the switch to the AC1 inputs 
should be no problem IF you can find a way to do it without sticking 
your #6 wires in the same lug as your 200A (probably 4/0 AL) feeders. 
That would work but be a NEC no-no.
Bob-O

>Dear Wrenches:
>
>My client's system is in California; he has two Bergey XL 1's on order, and
>has two Trace SW4024's and six 120W modules.  He is in a place with rolling
>power outages and wants back-up (vis a vis eight of the Surrette S460
>batteries).  His power is rarely out for more than an hour at a time.  His
>site offers excellent sun and winds, with 15 to 18 mph averages.
>
>But, he doesn't want a separate sub-panel for his important loads.  Has
>anyone done a grid-tie with a transfer switch (located before the main
>electrical service panel), where one side of the transfer switch is from
>utility power, and the other leg is 240VAC from the inverter's output?  My
>client wants total back up not just dedicated loads, and says he'll "power
>down" in the event of a power failure (and yes, I've cautioned him that if
>the grid fails, it would be easy to max out his inverters). There is no
>fuel generator integrated into this system.
>
>I've talked with a nice fellow from Asco (http://www.asco.com) about
>whether their transfer switches would work for this application.  We both
>think it would--but know of no one who's tested or tried this.
>
>One thing I'm uncertain about, code-wise, is feeding the utility input into
>the AC 1 "in", from the utility side of the transfer switch (like, with a
>separate 60A circuit breaker).
>
>Anybody got any ideas or experience with this type of system?  I'd
>appreciate any advice you could offer.
>
>Chris Daum
>Oasis Montana Inc.
>406-777-4321 or 4309
>406-777-2632  fax
>http://www.oasismontana.com

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