Trane Tracer ZN521 Installation And Operation Manual page 74

Chapter 7 Troubleshooting
Table 17. Fan does not energize (Continued)
Probable cause
Cycling fan operation/
continuous
Unoccupied operation
Fan mode off
Requested mode off
Table 18. Valves remain closed
Probable cause
Unit wiring
Failed end device
No power to the con-
troller
Power-up control-wait
Diagnostic present
Normal operation
Unit configuration
Manual output test
Random start
observed
Requested mode off
Entering water
temperature
sampling logic
Valve configuration
64
The controller operates the fan continuously when in the occupied, occupied standby, or
occupied bypass mode. When the controller is in the unoccupied mode, the fan is cycled
between high speed and off with capacity.
Even if the controller is configured for continuous fan operation, the fan normally cycles
with capacity during unoccupied mode. While unoccupied, the fan cycles on or off with
heating/cooling to provide varying amounts of heating or cooling to the space.
If a local fan mode switch determines the fan operation, the off position controls the fan
off.
You can communicate a desired operating mode (such as off, heat, and cool) to the con-
troller. If off is communicated to the controller, the unit controls the fan off. There is no
heating or cooling.
The wiring between the controller outputs and the valve(s) must be present and correct
for normal valve operation. Refer to applicable wiring diagram.
The valves must be checked to ensure proper operation.
If the controller does not have power, the unit valve(s) will not operate. For the Tracer
ZN521 controller to operate normally, you must apply an input voltage of 24 Vac. If the
green LED is off continuously, the controller does not have sufficient power or has failed.
If power-up control-wait is enabled (non-zero time), the controller remains off until one of
two conditions occurs:
1) The controller exits power-up control-wait after it receives communicated information.
2) The controller exits power-up control-wait after the power-up control-wait time expires.
Several diagnostics affect valve operation. For information about these diagnostics, see
Table 16 on page 59.
The controller opens and closes the valves to meet the unit capacity requirements.
The controller must be properly configured based on the actual installed end devices and
application. If the unit configuration does not match the actual end device, the valves
may not work correctly.
The controller includes a manual output test sequence you can use to verify output oper-
ation and associated output wiring. However, based on the current step in the test
sequence, the valves may not be open. Refer to the "Manual output test" on page 52.
After power-up, the controller always observes a random start from 5 to 30 seconds. The
controller remains off until the random start time expires.
You can communicate a desired operating mode (such as off, heat, and cool) to the con-
troller. If off is communicated to the controller, the unit controls the fan off. There is no
heating or cooling.
The controller includes entering water temperature sampling logic, which is automati-
cally initiated during 2-pipe and 4-pipe changeover if the entering water temperature is
either too cool or too hot for the desired heating or cooling. (See "AI1: Entering water
temperature" on page 17.)
Make sure the valves are correctly configured, using the Rover service tool, as normally
open or normally closed as dictated by the application.
Explanation
Explanation
CNT-SVX07C-EN