I want to find and purchase two automatic transfer switches so two 240V 100A supplies can back each other up. No generator is used, so I don't need generator controls or time delays.
Just use a regualr ATS and only feature you will not be using ise generator start/stop singals.
But you still need timer fortransferring back and forth after adequate time delays to see the voltage/freq is stable after return of a source. Also you want to make sure that the outage is permannet (not momentary dip) before you tranfer to other source.
Plus a standard product will maintain UL listing etc...