Auto-Zone Control Systems Auto-Zone Basic Systems Installation & Operation (Version 02C) - Manual (Page 24)

Section 1 Auto-Zone Basic
1-18 Design Guide
Relay Expansion Board
The following describes the operation of each of the relays on the optional relay
expansion board. You can choose the appropriate relays for any given application.
Relay #1 - Parallel Fan
If the Zone is in cooling mode or vent mode, the parallel fan can activate any time the
zone temperature drops 0.5
°F below the heating setpoint. It de-activates when the
temperature rises 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 any time 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 handling unit. 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 any time 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 an attempt to satisfy its own heating needs before creating a heating
demand at the Zone Manager.
Relay #4 - Series Fan
The series fan runs any time the main fan is running. This includes occupied and
unoccupied modes. The fan can only start running when the zone damper is closed, so it
determines that the damper is closed before starting the fan.