The Model KLB is designed to maintain optimum occupant comfort by varying the amount of cold air from the constant volume air handler and bypassing the excess cooling air back to the air handler. The KLB responds to the thermostat demand for cooling by varying the position of the unit damper, which in turn controls the amount of air entering a zone. During reduced loads, the damper position changes to deflect supply air into the ceiling plenum or return air duct. In this way, the air handler operates at constant volume, while individual zones benefit from increased control of comfort levels.

Savings result from the elimination of variable speed drives for the air handling system fan(s). At reduced zone loads, cool primary air is returned to the air handler via the plenum or return air duct without experiencing zone heat gains. The lower return air temperature allows the air handler to operate more efficiently.