I decided to connect my generator to the house and simulate what OP is describing. Mine is a model 64514, similar to his. What I found really doesn't surprise me, but good to know, and not good.
With typical loads: fridge, TV, satellite receiver, satellite internet modem and router, charging 1 phone and 1 laptop.
All measurements using Kill A Watt P3
L1-123.4V
L2-120.6V
60.6Hz
1200W Microwave on L1, 600W coffee pot on L2.
NOTE: MW is specified as 1200 working watts. The P3 flashes 1700 during operation, indicating the actual load is greater than the P3 1500W rating. However, 8oz of water was placed in the MW. MW was operated for 30sec during each test and operated as expected. The water warmed up each time.
Coffee pot ON, L1-123.4V, L2-117.8V 60.3Hz
MW & pot ON, L1-120.6V, L2-126.5V 59.8Hz
Now here's the kicker
Just MW ON, L1-120.6V, L2-133.2V 60.4Hz
With a heavy load on L1 and little load on L2, L2 goes over 130V
End of Test
Yea, I'm bored
