Sequence of operation
CNT-SVX04A-EN
67
Modulating outdoor air damper operation
The controller operates the modulating (3-wire floating) outdoor air damper
according to the effective occupancy, outdoor air temperature (communicated
or hardwired sensor), space temperature, effective setpoint, discharge air
temperature, and discharge air temperature setpoint. Default minimum damper
positions are provided and can be changed (using Trane's Rover service tool)
for occupied and occupied standby modes, and for low=speed fan operation.
The controller can also receive a communicated outdoor air minimum position
from Tracer Summit. See Table 39 below and Table 40 on page 69.
A communicated minimum position from Tracer Summit has priority over all
configured setpoints. When a communicated minimum position is not present,
the controller uses the configured minimum for low fan speed whenever the
fan is running at low speed, regardless of the occupancy state.
Table 39
Determining the economizer damper minimum position setpoint
During occupied modes, the damper remains at a minimum damper position,
whether a configured minimum position or communicated from Tracer
Summit, unless ASHRAE Cycle 1, ASHRAE Cycle 2, or economizer functions are
active.
ASHRAE Cycle 1 conformance
ASHRAE cycle 1 admits 100% outdoor air at all times except during a warm-up
cycle. To set up the Tracer ZN.520 zone controller for ASHRAE cycle 1
conformance, set the occupied outdoor air damper minimum position to 100%
open. During occupied periods, the modulating damper opens 100%.
If the space temperature drops 3ºF below the active setpoint, the Tracer ZN.520
zone controller closes the outdoor air damper regardless of the active minimum
damper position.
Occupancy
Tracer Summit
setpoint
Fan speed
Active minimum setpoint
Unoccupied
Any value
Any value
0%
Occupied
Occupied bypass
Occupied standby
Valid
Any value
Tracer Summit
Occupied
Occupied bypass
Occupied standby
Invalid
Low
Occupied low fan minimum
Occupied
Occupied bypass
Invalid
Med/high
Occupied minimum
Occupied standby Invalid
Med/high
Occupied standby minimum
