Tried to wire the 3 kw set into the garage to test for possible use during a power outage. The terminals show the correct voltage of 240 volts between the L1 and L2 terminals with the switch in the correct position, so I wired up the L1 and L2 terminals to the hot legs of the fuse box and the ground to the ground. When we tried to run the garage, it acted like a low voltage on one or both legs, burnt up the heater PC board and overloaded a couple of motors that were on (but no problems). Anyone got any ideas? Unit works great on 120 volts with a plug hooked to L1 and L2.