Trane Tracer ZN.520 Manual page 99

CNT-SVX04A-EN
Troubleshooting
Table 62 Valves stay 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.
Random start After power-up, the controller always observes a random start
observed from 5–30 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.
Power-up control When power-up control wait is enabled (non-zero time), the
wait controller remains off until one of two conditions occurs:
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 Table on page 92.
Manual output test The controller includes a manual output test sequence you can use
to verify output operation and associated output wiring. However,
based on the current step in the test sequence, the valve(s) may
not be open. Refer to "Manual output test" on page 88.
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.
Requested mode off You can communicate a desired operating mode (such as off, heat,
and cool) to the controller. When Off is communicated to the
controller, the unit controls the fan off. There is no heating or
cooling (valves are closed).
Sampling logic 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. Refer to
"Entering water temperature sampling function" on page 59.
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 re-attempt sampling
routine.
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