Trane UniTrane Installation Operation & Maintenance page 110

Table 45—Continued. Fan Outputs not Energizing
Probable Cause
No power to the TUC
Autocycle test
Wiring
Table 46. Valves Closed
Probable Cause
Normal operation
unit disabled
Override present
Latching diagnostic presen
Autocycle test
Maximum heating/cooling
capacity of zero
110
Explanation
The TUC requires 24 VAC power for the unit to
operate properly.
The controller includes an auto cycle test sequence that verifies
analog and binary output operation and associated output wiring.
However, based on the current stage in the test sequence, supply
fan may be off. Refer to the "Autocycle Test" section on page 71.
The wiring between the controller outputs and the fan relays and
contacts must be present and correct for normal fan operation.
Refer to the typical unit wiring diagrams on pages 105-106.
Explanation
The valves open and close to meet unit capacity requirements.
• The TUC may be disabled via the shutdown mode on a Tracer
system or if BIP1 is configured as external interlock.
• During the stop modes, the valves remain closed unless freeze
avoidance is enabled and the fresh air temperature falls
below the freeze avoidance setpoint (configurable).
• If the fresh air temperature falls below the freeze avoidance
setpoint, the valves open. The TUC enables freeze avoidance
whenever the freeze avoidance setpoint is not zero.
The valves may be overridden to the closed position by either the
Tracer ® system or by Everyware™ software. Whenever any override
is active, the TUC drives the valves closed unless they are concur-
rently overridden open.
A specific list of diagnostics effects valve operation. For more
information, see the "Diagnostics" section on page 73. Latching
diagnostics require a manual reset to restore normal unit operation.
The controller includes an autocycle test sequence that verifies
analog and binary output operation and associated output wiring.
However, based on the current stage in the test sequence, the
valve(s) may be closed. Refer to the "Human Interface" section on
page 62.
®
The Tracer may limit the maximum heating/cooling capacity of the
TUC from zero to 100%. When the maximum cooling capacity is
zero, the cooling valve remains closed. When the maximum heating
capacity is zero, the heating valve remains closed.
Terminal Unit
Control (TUC)
UNT-IOM-6
®