A roof air will start at 102 volts but I don't have that kind of money (to put out the fire and replace the compressor after a short while doing that). To be more explicit, a generator that will high-head start a roof air and slump to a minimum of 108 volts. I've seen windings turn from a nice varnish yellowish amber to black in three seconds. Starting caps assist help but that 108 volts is it. I'd like to see somebody test this with any 2K rated unit. My 5500 diesel running through a transformer (to use both phases) use to slump to 111 volts on high head restart.