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UNT-IOM-6 55
Tracer
®
ZN.010
and ZN.510
Table 17. Valves Stay Open
Probable Cause Explanation
Normal operation The controller opens and closes the valves to meet the unit capacity require-
ments.
Valve override The controller can communicate a valve override request to affect the
valve operation.
Manual output test The controller includes a manual output test sequence that verifies analog and
binary output operation and the associated wiring. However, based on the
current step in the test sequence, the valves may be open. Refer to the Manual
Output Test section on page 51.
Diagnostic present A specific list of diagnostics affects valve operation. For more information, see
the Diagnostics section on page 50.
Sampling logic The controller includes entering water temperature sampling logic that automati
cally invokes during 2-pipe or 4-pipe changeover to determine if the
entering water temperature is correct for the unit operating mode. Refer to the
Entering Water Temperature Sampling section on page 41.
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 device, the valves may not work correctly.
Unit wiring The wiring between the controller outputs and the valve(s) must be present and
correct for normal valve operation. Refer to the typical unit wiring diagrams in
the Appendix of this manual.