Abstract: A control is functional to perform a method of determining a maximum desired airflow for each of a plurality of zones in a multi-zone HVAC system, and an expected airflow to those zones. In part, these determinations are based upon an algorithm that calculates the relative size of the ducts leading to each of the zones. The expected and maximum airflows are compared for each of the zones, and if any zone has an expected airflow that exceeds its maximum airflow, certain steps are taken to reduce airflow to that zone.

Abstract: A device and method for controlling the conditioning of air in the zones of a forced air HVAC system. The device comprises thermostats located in at least two different zones, air ducts and dampers located therein to control the flow of air to the different zones. The microprocessor receives signals from the thermostats corresponding to perceived temperatures in the zones and compares the perceived temperatures to predetermined temperatures and determines a trajectory for each of the zones. The microprocessor in turn sends signals to the dampers corresponding to a positions between fully open and fully closed to control the amount of conditioned air through the ducts such that each of the zones follows the trajectory and reaches the predetermined temperatures at about the same time. The microprocessor further determines system demand and turns the HVAC system on and off in response to the system demand.