Trane CNT-SVX07C-EN, Zone Controller, N512 manual Troubleshooting, Valves remain closed

Chapter 7 Troubleshooting

Table 17. Fan does not energize (Continued)

Probable cause	Explanation
Cycling fan operation/	The controller operates the fan continuously when in the occupied, occupied standby, or
continuous	occupied bypass mode. When the controller is in the unoccupied mode, the fan is cycled
	between high speed and off with capacity.
Unoccupied operation	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.
Fan mode off	If a local fan mode switch determines the fan operation, the off position controls the fan
	off.
Requested mode 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.

Table 18. Valves remain closed

Probable cause	Explanation
Unit wiring	The wiring between the controller outputs and the valve(s) must be present and correct
	for normal valve operation. Refer to applicable wiring diagram.
Failed end device	The valves must be checked to ensure proper operation.
No power to the con-	If the controller does not have power, the unit valve(s) will not operate. For the Tracer
troller	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.
Power-up control-wait	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.
Diagnostic present	Several diagnostics affect valve operation. For information about these diagnostics, see
	Table 16 on page 59.
Normal operation	The controller opens and closes the valves to meet the unit capacity requirements.
Unit configuration	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.
Manual output test	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.
Random start	After power-up, the controller always observes a random start from 5 to 30 seconds. The
observed	controller remains off until the random start time expires.
Requested mode 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.
Entering water	The controller includes entering water temperature sampling logic, which is automati-
temperature	cally initiated during 2-pipe and 4-pipe changeover if the entering water temperature is
sampling logic	either too cool or too hot for the desired heating or cooling. (See “AI1: Entering water
	temperature” on page 17.)
Valve configuration	Make sure the valves are correctly configured, using the Rover service tool, as normally
	open or normally closed as dictated by the application.

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