Trane ZN.520 manual Troubleshooting, Valves stay closed, Probable cause, Possible Explanation

Troubleshooting

Valves

Table 30: Valves stay closed

Probable cause	Possible Explanation
Unit wiring	The wiring between the controller outputs and the valve(s) must be present and correct for normal
	valve operation.
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.
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 valves may not work correctly.
	When power-up control wait is enabled (non-zero time), the controller remains off until one of two
Power-up control	conditions occurs:
wait	The controller exits power-up control wait once it receives communicated information.
	The controller exits power-up control wait once the power-up control wait time expires.
Diagnostic present	A specific list of diagnostic affects valve 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 valve(s) 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 valves to close.
	You can communicate a desired operating mode (such as OFF, HEAT, and COOL) to the controller. When
Requested mode off	OFF is communicated to the controller, the unit controls the fan OFF. There is no heating or cooling
	(valves are closed).
	The controller includes entering water temperature sampling logic which is automatically invoked
	during 2-pipe and 4-pipe changeover when the entering water temperature is either too cool or too hot
	for the desired heating or cooling. For more information see, Entering Water Temperature Sampling,
Sampling logic	on page 43 for more information.)
	Example: A 2-pipe heat/cool changeover unit will not cool if the entering water temperature is too
	warm for cooling or if the entering water sensor is not present. The unit will not heat if the entering
	water temperature is too cool for heating. If failed the controller will close valve for one hour then
	reattempt sampling routine.
Table 31: Valves stay open
Probable cause	Possible Explanation
Unit wiring	The wiring between the controller outputs and the valve(s) must be present and correct for normal
	valve 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 valves may not work correctly.
Diagnostic present	A specific list of diagnostic affects valve 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 valve(s) may be
	open.For more information see, Manual Output Test, on page 48 for more information.)
	The controller includes entering water temperature sampling logic which automatically invoked during
Sampling logic	2-pipe and 4-pipe changeover when the entering water temperature is either too cool or too hot for the
	desired heating or cooling. For more information see, Entering Water Temperature Sampling, on page
	43 for more information.)

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