the temperature of air leaving a cooling coil is monitored for dropping below various threshold values . the number of cooling stages which chill the refrigerant flowing through the cooling coil is first reduced when the temperature drops below a first threshold and continues to drop relative to a previously sensed temperature . damper positions governing the amount of air flowing to zones to be cooled are thereafter adjusted when the temperature continues to drop relative to a previously sensed temperature . all adjusted positions are at least maintained relative to a calculated offset value until the temperature rises above a second threshold value greater than the first threshold value . all cooling stages are turned off if the sensed temperature drops below a third threshold value lower than the first threshold .