Zone demand controlled dual heat pump system and controller therefor

A thermal zone demand controlled dual cascade arranged heat pump system and system controller for building spaces, comprising:

• (a) a pair of heat pumps being located externally of the building space;
• (b) a plurality of thermostats each being located within a respective one of said thermal zones for sensing the temperature of air therein, said thermostats each having low speed and high speed blower control circuits each becoming electrically energized at a predetermined temperature range, one of said thermostats being a main thermostat and having a mode selector switch for selection of a "cool" mode, a "heat" mode and an "off" mode;
• (c) a conditioned air supply and return assembly having a conditioned air chamber, an air return plenum and a plurality of air supply conduits for conducting conditioned air from said conditioned air chamber to respective thermal zones;
• (d) a plurality of thermal zone air supply blowers each being situate for moving conditioned air from said conditioned air chamber through respective air supply conduits to respective thermal zones and each having low speed and high speed operating coils;
• (e) a pair of heat transfer refrigerant coils being interconnected respectively with said pair of heat pumps and being located in series within said conditioned air chamber upstream of said air supply conduits;
• (f) an air return blower being located within said conditioned air chamber and forcing air from said air return plenum into said conditioned air chamber;
• and
• (g) electronic heat pump and blower control circuitry being conditionable to select one of said heat pumps as the primary heat pump for operation to accommodate a predetermined thermal load and to select the other of said heat pumps as the secondary heat pump for operation simultaneously with said primary heat pump to accommodate thermal load in excess of said predetermined thermal load, said electronic heat pump and blower control circuitry also being conditionable for reversing said primary and secondary selection of said pair of heat pumps, said electronic heat pump and blower control circuitry further having a plurality of zone control circuits each being electronically coupled with one of said plurality of thermostats for thermal zone and thermal load controlled zone blower and heat pump control signals.