Auto-Zone Plus
Section 2
Design Guide 2-31
Zone Controller Auxiliary Relay Board
Operation
Relay #1 - Parallel Fan
If the zone is in cooling mode or vent mode, the parallel fan can activate anytime the
zone temperature drops 0.5°F below the heating setpoint. It de-activates when the
temperature rises 0.5°F above the heating setpoint. The space temperature must be below
the AUX HEAT setpoint in the occupied mode before the Parallel Fan relay can be
energized.
Relay #2 - Box Heat
If the zone is in cooling mode or vent mode, the box heat can activate anytime the zone
temperature drops 1.5°F below the heating setpoint. It de-activates when the temperature
rises to within 1.0°F of the heating setpoint. Box heat is not allowed to activate in the
heating mode when there is hot air being supplied by the air handler. This output was
intended to allow zone re-heat while the Zone Manager is satisfying cooling demands in
other zones. The space temperature must be below the AUX HEAT setpoint in the
occupied mode before the Box Heat relay can be energized.
Relay #3 - Aux Heat
In the occupied mode, the aux heat can activate anytime the zone temperature is 0.5°F
below the aux heat setpoint. It de-activates when the temperature rises 0.5°F above the
aux heat setpoint. In the unoccupied mode, the aux heat uses the unoccupied heating
setpoint with the same deadband values mentioned above. This prevents the zone from
maintaining the same aux heat setpoint at night that it does during the daytime.
This output was intended to allow zone heating, to augment the normal heating mode and
also to allow a zone to attempt to satisfy its own heating needs before creating a heating
demand at the Zone Manager.
Relay #4 - Series Fan
The series fan runs anytime the main fan is running. This includes occupied and
unoccupied modes. In the unoccupied mode, the fan can only start when the zone damper
is closed. The controller checks to be sure the damper is closed before starting the fan.
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