I had a brand new G71MPP installed this past Monday and have studying the diagnostic LED (can you say "obsessive compulsive"). I've noticed that when my tstat (Honeywell TH8321U) calls for heat:
1. It always runs the vent calibration routine as indicated by CAL,
2. Then the pre-purge/ignition warm up as indicated by blinking a series of flashing H's.
3. Finally it fires the burners and spins up the blower
The install manual seems to suggest that vent calibration *may* be initiated by an initial call for heat, and while I have not been able to observe EVERY heating call...I've seen this sequence every time so far. Have other G71 owners observed this? Is it normal?