Recently had my 35 year old Federal Pacific service entrance replaced. As I was labelling the circuits, I found that the 15 amp furnace fan circuit also has a bunch of lights on it. If I add them all up plus the 12 amps for the fan (that's what's on the fan label and I assume it's the max load at startup), I come up with about 2200 watts.

I know that's way more than the 1800 available from a 15 amp circuit but they are never all on at the same time and I've never blown the breaker. It would be unusual for more than about 300 watts worth of lights to be one at the same time.

Should I move some things off that circuit anyway? Should the furnace fan have its own dedicated circuit?