A friend lost power at his house due to the heavy snow here, and I offered to let him use my 4kw contractors generator to power the furnace. The house has no master transfer switch nor did it have any outlets on the same circuit as the furnace, which is hardwired.

I figured it would be sufficient isolation (from the utility company) if we turned the master (200A) breaker to the OFF position.

The plan was to supply 15-20 amps for the entire house by making up an AWG 14 (or AWG 12) cable with male 3-prong connectors at both ends, and use it to connect the generator with any household outlet on a 15 or 20 amp circuit. The plan also included turning off all non-essential lights and appliances, and unplug the refrigerator (to avoid a surge) before plugging in power. I figured if the load got too heavy for safety it would pop the breaker for the one circuit the generator was powering, or the built-in breaker in the generator.

We never got to test it because power came back on before we did this, but I got as far as making the male/male cable. I figured the biggest risk would be if the powered cable was unplugged from the wall and there would be an unsafe set of exposed prongs.

Is there anything else wrong with this idea?