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UV-SVP01A-EN 56
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.
Power-up control
wait
When power-up control wait is enabled (non-zero time), the 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, Tracer™ ZN.520 Unit
Controller diagnostics, on page 52 for more information.)
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. 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.
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. For more information see, Entering Water Temperature Sampling,
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.)
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 be
open.For more information see, Manual Output Test, on page 48 for more information.)
Sampling logic
The controller includes entering water temperature sampling logic which 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, on page
43 for more information.)