The
zone control system allows a single HVAC unit to have separate
temperature zones in the house (the number of zones allowed
is determined by the zone control equipment manufacturer and
the HVAC contractor). Each zone is controlled by its own space
thermostat and motorized zone damper. If any of the zone thermostats
call for heating or cooling, the zones not calling will have
their dampers powered closed, and the zone(s) calling will
have its (their) damper(s) remain open. The heating or cooling
equipment will also be brought on at the same time. When all
zone thermostats are satisfied, the heating or cooling equipment
turns off and all zone dampers return to the open position
to allow for continuous air circulation.
If
one of the zone thermostats is calling for heating and another
zone thermostat is calling for cooling, the one calling for
cooling will take priority and the system will operate in
the cooling mode. When the thermostat that is calling for
cooling is satisfied, the system will change over and take
care of the heating requirement. This is referred to as "Auto
Changeover - Cooling Priority." Other systems offer "Auto
Changeover - Heating Priority" and "First Call Priority"
