My old furnace got condemned so I had a new Payne PG96VAT installed. The installer said my old Honeywell CT3300 would be just fine. I'm not so sure.
The t-stat was set with screws A and B both in. I think these screws affect the duty cycle it will let the furnace run but it really is not explained in the manual. I know even with the old furnace that if I jacked up the setpoint, the furnace would not run continuously like it would with a mercury bulb t-stat.
Anyway... with the new furnace being two stage, the t-stat is messing with how the second stage comes on now that it is getting a little colder. It will kick up to the second stage just about the time the t-stat decides the furnace ran long enough and it withdraws the call for heat despite the setpoint not having been reached.
Page 7 of the Honeywell manual says for over 90% AFUE A should be out one turn so I changed it but now have to wait for a cold morning to see how it will react. Anyone care to hazard a guess what the outcome will be for turning screw A out?
Me, personally would like to toss this old POS t-stat but for some reason the wife thinks it's a good one based on what the installer said. She distrusts all the newer stuff.
Oh, I also read on page 2 in the Honeywell manual that this model is not compatible with a multi-stage furnace. Am I wasting my time with it?