Installation and Maintenance Manual

Startup
94 UNT-SVX07D-EN
longer. At 100 percent capacity, the heating valve is fully
open (modulating valves) or on continuously (two-
position valves).
The Tracer ZN520 fan output(s) normally run continuously
during the occupied and occupied standby modes, but
cycle between high and off speeds with heating/cooling
during the unoccupied mode. When in the occupied mode
or occupied standby mode and the fan speed is set at the
high, medium, or low position, the fan runs continuously
at the selected speed. Refer to the Troubleshooting section
for more information on abnormal fan operation.
When the unit’s supply fan is set to auto, the controller’s
configuration determines the fan speed when in the
occupied mode or occupied standby mode. The fan runs
continuously at the configured heating fan speed or
cooling fan speed. For all fan speed selections except off,
the fan cycles off during unoccupied mode.
The economizer outdoor air damper is never used as a
source of heating. Instead, the economizer damper (when
present) is only used for ventilation; therefore, the damper
is at the occupied minimum position in the occupied
mode. The damper control is primarily associated with
occupied fan operation.
Fan Mode Operation (Tracer ZN520)
For multiple fan speed applications, the Tracer ZN520
controller offers additional fan configuration flexibility.
Separate default fan speeds for heating and cooling
modes can be configured. The fan runs continuously for
requested speeds (off, high, medium, or low). When the
fan mode switch is in the Auto position or a hard-wired fan
mode input does not exist, the fan operates at the default
configured speed. See Table 25, p. 94 for default fan
configuration for heat and cool mode. During unoccupied
mode, the fan cycles between high speed and off with
heating and cooling fan modes. If the requested speed is
off, the fan always remains off.
During dehumidification, when the fan is on Auto, the fan
speed can switch depending on the error. Fan speed
increases as the space temperature rises above the active
cooling setpoint.
Additional flexibility built into the controller allows you to
enable or disable the local fan switch input. The fan mode
request can be either hard-wired or communicated to the
controller. When both are present, the communicated
request has priority over the hard-wired input. See
Table 26, Table 27, and Table 28.
Continuous Fan Operation (Tracer ZN520)
During occupied and occupied standby modes, the fan
normally is on. For multiple speed fan applications, the fan
normally operates at the selected or default speed (off,
high, medium, or low). When fan mode is auto, the fan
operates at the default fan speed.
During unoccupied mode, the controller controls the fan
off. While unoccupied, the controller heats and cools to
maintain the unoccupied heating and cooling setpoints. In
unoccupied mode, the fan is controlled on high speed only
with heating or cooling.
The unit fan is always off during occupied, occupied
standby, and unoccupied modes when the unit is off due
to a diagnostic or when the unit is in the off mode due to
Table 25. Fan configuration (Tracer ZN520)
Auto Fan Operation Fan Speed Default
Heating Continuous Off
Low
Medium
High
Cooling Continuous Off
Low
Medium
High
Table 26. Local fan switch enabled (Tracer ZN520)
Communicated Fan Speed
Input
Fan Switch
(Local)
Fan
Operation
Off Ignored Off
Low Ignored Low
Medium Ignored Medium
High Ignored High
Auto Off
Low
Medium
High
Auto Off
Low
Medium
High
Auto (configured default, determined by heat/cool mode)
Table 27. Fan operation in heating and cooling modes
(Tracer ZN520)
Fan Mode
Heating Cooling
Occ. Unocc. Occ. Unocc.
Off Off Off Off Off
Low Low Off/high Low Off/high
Medium Med Off/high Med Off/high
High High Off/high High Off/high
Auto Default fan sp. Off/high Default fan sp. Off/high
Table 28. Local fan switch disabled or not present (Tracer
ZN520)
Communicated Fan Speed Input Fan Operation
Off Off
Low Low
Medium Medium
High High
Auto (or not present) Auto (fan runs at the default speed)
UNT-SVX07_-EN.book Page 94 Friday, April 27, 2012 9:40 AM