The module inside the ATS is nothing more then dry contacts that are controlled by load conditions. You don't necessarily even need to use their relay components if you didn't want to, something like RIB (relay in a box) could be about as easily used. All you are running to the load shed terminals is 24 volt control circuits to a relay that controls the load to be shed. Many HVAC loads are simple and don't require the relay module because they already have 24 volt control circuitry, you just extend this control circuit to the load shed terminals of the ATS.
I might have been a little wrong before, AC1 and AC2 I are terminals to NC contacts the others I believe their intention is to install a 24VAC transformer within the ATS, and tie the output of it to the load supply terminals. You then have 24 VAC (L1 and L2) on each "load 1-4 output terminals to run to a 24 volt relay to control the desired load. Design should still be NC contact - so that the load runs when control module is in state of rest - which it should be at all times when generator isn't running.
Might depend on whether you want back up heat to be able to run or not, if other then electric heat. Same for gas furnace - interrupting thermostat common wouldn't allow heat to run, just interrupting AC contactor - only prevents compressor from running.
It doesn't monitor AC load. Was already mentioned earlier - it monitors total generator load and when it gets too high it starts to shed loads. This way loads that are not connected to shedding module are by default given priority, the controlled loads are only allowed to run when the total load is low enough to let them run. There are delays and other schemes to turn them back on when total load is reduced again.
Good point.
For that matter if one has a heat pump with electric backup heat you could easily connect the "W" lead through one of the A/C load shed circuits and it would cut off the electric heat. If generator isn't large enough to run the back up heat at all, you maybe somehow set it up to always shed the heat circuit whenever on standby power. Simplest is to just not feed the heat circuit out of the panel the ATS supplies if there is only one panel supplied by the standby system, but there are other ways if only one panel is being supplied.
Then you likely only interested in controlling the AC compressor.
