I've searched and searched the forum but couldn't find a clear cut answer (at least to me!!) for this.
We will have a 20 amp hook-up for a week in Maine and it will be chilly at night. I know I can't use heat pump/ac, but can 20 amps power the propane furnace (Suburban NT-26SEQ) safely?
Oh sure. No problem whatsoever. It depends on your converter, but typically it won't pull more than around 8-11 amps full out off your 20amp 110vac line.
You should not have a problem running the furnace. It runs from 12v for the fan and the propane provides the heat so the draw on the 20amp AC is low. The furnace only pulls 10amp DC that is around 1 amp AC.