We have an Air Ease Ultra80 oil furnace. (combo forced air heat/AC system). Model # LUF80A112/125D20-2 A

Last summer I installed a LUX programmable thermostat (TX9100E).

Had no issues with cooling in summer.

Now that the heat is coming on, I noticed it is cycling differently than before.

The furnace always had a purge cycle at end of heat cycle, but now it seems that the unit is going through a short cycle BEFORE the heat cycle as well: furnace fan comes on, runs for a few seconds (with NO HEAT produced), then shuts off. Then, a few seconds later, fan AND burner come on, run a normal heat cycle, then a purge.

I was wondering if this is a single or two-stage furnace, and I might have the stat wired for the wrong one? I assumed it was a single stage, and wired it according to instructions for a single-stage. Can anyone confirm if this model is a single stage?