Straightedge,
It's not on you or your company, unless the disconnects were on, thermostats were installed and left on, prior to phase checking, AND the A/C guys notified you of this, AND you signed a waiver accepting responsiblity for it.
ALL trades acccept responsibility for their work and equipment until final inspection and acceptance by the GC or final customer.
If the power company hooked you up the wrong voltage, and you didn't check it prior to powering up, and you smoked all your panels, lights and ect, are you going to blame the power company?
The A/C contractor should of had his guys check incoming power, double check rotation, and installation prior to enabling the equipment.
He don't have a leg to stand on. He is trying to see if you'll pay for his mistake.
Keep in mind the power outage senario. If they burn up due to a sag, that's on the engineering outfit. You just ran what they spec'd out.
