I didn’t want to hijack the other active generator threads.

I have the opportunity to buy a brand new, 100amp Generac load center automatic transfer switch for cheap. I currently don’t have a standby generator, but would like one in the future. Am I able to have this installed, and use a portable gennie that only pushes 30amps? Basically, can I use an automatic transfer switch with a portable generator instead of a standby? I’m having a surprisingly difficult time finding my answer elsewhere on the web. I realize I’ll have to selectively energize only certain circuits, but it’d be nice to only have to do this portion once. Thanks.

Yes you can use it. It has a manual throw arm.

Depending on the size of your existing service you will need to separate circuits and put in a sub panel.
Reason being 100 amp is probably too small for your entire panel, and if it is switching your entire panel it has to be “service rated”

I can go into more detail but I would need more info on your current setup.

RXG16EZA1 is what I’d be getting. Seems to be a pre-wired 16 circuit sub panel with a built in ATS. My home is new construction, with 200amp service. I had intended on only feeding necessary circuits, and not my whole panel.

Define "Cheap".  I would buy it; depending on price.  

I don't see why you could not use it.  If you have a 240 output on the genny, simply install the transfer switch with an plug outside then just plug the genny in.  It would be very easy to convert to a whole house generator when you make that purchase later on.

Bill

The spec sheet has that listed as an 85 amp panel, which is an odd size.

You can feed this with a 60 or 70 amp breaker from your main panel for the utility side feed.
All of the circuits that you want on the gen will connect to these breakers.
It is capable of up to a 16kw genset.

Someone else more familiar with the generac switches will need to comment on this ATSs ability to automatically connect to the energized bus. I believe when you loose power, then plug in your gen it will automatically switch to the secondary feed.

Mount it beside your 200A panel and connect with ENT conduits. Feed with a plug in 100A breaker from existing panel. Run critical circuits from 200A over to 100A. Then use a generator inlet box for emergency power feed. When you get a better generator you can use the start circuit to make it auto.