Trane Tracer Unit Ventilator, ZN.520 manual DX/Electric Heat, Outside Air Damper

Troubleshooting

Table 31: Valves stay open

Probable cause	Possible Explanation
	When the fan is off with no demand for capacity (0%) and the outdoor air temperature is below the
Freeze avoidance	freeze avoidance setpoint, the controller opens the water valves (100%) to prevent coil freezing. This
	includes unoccupied mode when there is no call for capacity or any other time the fan is off.

Normal operation

The controller opens and closes the valves to meet the unit capacity requirements.

DX/Electric Heat

Table 32: DX or electric output(s) does not energize

Probable cause	Possible Explanation
Unit wiring	The wiring between the controller outputs and the end devices must be present and correct for normal
	operation.
Unit configuration	The controller must be properly configured based on the actual installed end devices and application.
	When the unit configuration does not match the actual end devices, the unit may not work correctly.
Diagnostic present	A specific list of diagnostics affect compressor and electric heat operation. For more information see,
	Tracer™ ZN.520 Unit Controller diagnostics, on page 52 for more information.)
	The controller includes a manual output test sequence you can use to verify output operation and
Manual output test	associated output wiring. However, based on the current step in the test sequence, the DX or electric
	outputs may be OFF. For more information see, Manual Output Test, on page 48 for more information.)
	When the fan is OFF with no demand for capacity (0%) and the outdoor air temperature is below the
Freeze avoidance	freeze avoidance setpoint, the controller disables compressors and electric heat outputs. This includes
	UNOCCUPIED mode when there is no call for capacity or any other time the fan is OFF.
Normal operation	The controller energizes the outputs only as needed to meet the unit capacity requirements.

Outside Air Damper

Table 33: Outdoor air damper stays closed

Probable cause		Explanation
Unit wiring	The wiring between the controller outputs and the outdoor air damper must be present and correct for
	normal damper operation.
	The controller must be properly configured based on the actual installed end devices and application.
Unit configuration	When the unit configuration does not match the actual end devices, the damper may not work
	correctly.
Random-start observed	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.
	When power-up control wait is enabled (non-zero time), the controller remains OFF until one of two
	conditions occurs:
Power-up control wait	1.	The controller exits power-up control wait once it receives communicated information.
	2.	The controller exits power-up control wait once the power-up control wait time expires.
Diagnostic present	A specific list of diagnostics affects outdoor air operation. For more information see, Tracer™ ZN.520
	Unit Controller diagnostics, on page 52 for more information.)
	The controller includes a manual output test sequence you can use to verify output operation and
Manual output test	associated output wiring. However, based on the current step in the test sequence, the unit damper
	may not be open. For more information see, Manual Output Test, on page 48 for more information.)
Fan mode OFF	When a local fan mode switch (provided on the Trane zone sensor) determines the fan operation, the
	OFF position controls the unit OFF and damper to close.

UV-SVP01A-EN 57