Trane Tracer ZN521 Installation And Operation Manual page 53

Table 19. Valves remain open (continued)
Probable cause
Entering water
temperature
sampling logic
Valve configuration
Freeze avoidance
Table 20. DX or electric heat does not energize
Probable cause
Unit wiring
Failed end device
No power to the
controller
Diagnostic present
Normal operation
Unit
configuration
Manual output test
Requested mode off
Freeze avoidance
Table 21. Outdoor air damper remains closed
Probable cause
Unit wiring
Failed end device
CNT-SVX07D-EN
The controller includes entering water temperature sampling logic, which is automatically
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
ture, " p. 16.)
Make sure the valves are correctly configured, using the Rover service tool, as normally
open or normally closed as dictated by the application.
When the fan is off with no demand for capacity (0%) and the outdoor air temperature is
below the freeze avoidance setpoint, the controller opens the water valves (100%) to pre-
vent coil freezing. This includes unoccupied mode when there is no call for capacity or
any other time the fan is off.
The wiring between the controller outputs and the end devices must be present and cor-
rect for normal operation. Refer to applicable wiring diagram.
Check the control contactors or the electric heat element, including any auxiliary safety
interlocks, to ensure proper operation.
If the controller does not have power, heat outputs do 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.
Several diagnostics affect DX and electric heat operation. For information about these
diagnostics, see Table 16, p.
The controller controls compressor or electric heat outputs as needed 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, DX or electric
heat may not operate 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 DX or electric heat outputs may be off. Refer to the
p. 43.
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 shuts off the compressor or elec-
tric heat.
When the fan is off with no demand for capacity (0%) and the outdoor air temperature is
below the freeze avoidance setpoint, the controller disables compressors and electric
heat outputs (100%) to prevent coil freezing. This includes unoccupied mode when there
is no call for capacity or any other time the fan is off.
The wiring between the controller outputs and the outdoor air damper must be present
and correct for normal outdoor air damper operation. Refer to applicable wiring diagram.
Check damper actuator to ensure proper operation.
Explanation
Explanation
49.
Explanation
Troubleshooting
"AI1: Entering water tempera-
"Manual output test, "
53