Quote Originally Posted by mirinex View Post
hi mark I am looking at the manual for the hz322 and it doesn't say anything about cooling only!
The zone control may drop the power to BK in both heating and cooling, but the control board in the furnace only responds to it when it is running in the cooling mode.
That function works the almost the same in every brand of furnace, with the only real difference being how much the airflow is reduced.

Adjustments can be made to the 1st and 2nd stage heating airflow with the user interface in the furnace, but there is a minimum required airflow for the furnace to operate correctly, so there are limits to how low it can be set.