here are my two cents (or a bit more).
As mentioned, Generac will not honor warranties for their current product line for off-grid applications. They are supposed to be coming out with a line (6-7KW I believe) that will be warranted for off-grid. The products will be available in 1Q next year (I think).
If you are off-grid and have a generac generator and want to start and stop it from your inverter, you have a few options.
1) Remove the control assembly and modify it. This involves unsoldering or removing the leads from the AUTO-OFF-MANUAL switch and installing a modification. I can supply diagrams to do this, but it is a modification that will prohibit you from replacing the control card under warranty.
2) Use an external 240VAC, 60Hz source to "fool" the generator into thinking it is receiving utility power. To start the generator, you simply interrupt the "utility" voltage and the generator will start and run until the utility voltage returns.
You cannot use the 240 (0r 120) VAC output from the inverter to do this. Consider, for a moment, the operational syntax of the inverter. In the invert mode, the inverter produces 120 or 240 VAC to supply loads in the dwelling. When the inverter senses an external AC input (from a generator, for example) it switches from the invert mode to the charge mode. As soon as this switch is made, the inverter stops producing an AC output.
So, if you connect the inverter's AC output to lines N1 and N2 of the generator, the generator will see a utility voltage and remain dormant. If you interrupt line N1 or N2, the generator will start. Now, at least, you've got the generator started and running and the batteries are charging.
OK, the batteries are now charged and the inverter signals the generator control to close the open line N1 or N2. The relay drops out but, there is no AC available from the inverter; it's still in charge mode. The generator is dumb; it simply keeps running because is detects no AC utility voltage on lines N1 and N2.
The only way to do this is to use a separate, self-contained source of 240VAC, 60 Hz. I have developed such a device and have it installed and operating in two off-grid applications.
Now, this ain't no sales pitch; I'm just trying to help. If anyone is interested in this gadget of mine, send an email to johnwhass @ aol.com
and I can send you some info. If you're a good electronic technician, you can probably build it yourself.
I also have wiring diagrams for most generac products.
If you want to use a different generator, I suggest you visit the web site of US Carbueration. They take standard Yamaha generators (up to 6600 Watts, I believe) and modify them to use propane, natural gas or gasoline. The generators can be started remotely. For propane use, they can be ordered with an automatic primer which ensures reliable starts, even in winter . I'm in the White Mountains of New Hampshire and they work well here.
I've put a lot of effort getting various types of generators to work with various off-grid systems. Drop me an email if you need help.