Trane UniTrane Installation Operation & Maintenance page 113

Table 49. Fresh Air Damper Closed
Probable Cause
Normal Operation
Unit Disabled
Override Present
Latching Diagnostic Present
Autocycle Test
Unit Configuration
Warm-Up Mode
Local Fan Switch: Off
No Power to the TUC
Motion Detection Feature
UNT-IOM-6
Explanation
• The two-position fresh air damper opens under normal unit operation
during occupied mode and closes during unoccupied mode.
• Modulating analog and 3-wire floating point economizers open to
the minimum position (configurable) when the unit is occupied and
modulate to meet unit capacity requirements.
• If the minimum damper position is zero, the damper may close for
extended periods. During the unoccupied mode, the normal fresh
air damper position is closed.
• Tracer
® may disable via the shutdown mode on a system or if
BIP1 is configured as external interlock.
• During the stop modes, the fresh air damper remains closed.
The fresh air damper may be overridden closed by either the
Tracer ® system or by Everyware™ software. Whenever any override
is active, the TUC drives the fresh air damper closed, unless the
damper is concurrently overridden open.
Specific diagnostics affect damper 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, the current test sequence stage may require the
damper to close. Refer to the "Autocycle Test" section on page 71.
The TUC cannot control fresh air damper outputs if the unit is config-
ured for no fresh air damper. Also, if the fresh air damper is incor-
rectly configured (on/off, modulating analog, or 3-wire floating point),
it may not operate properly.
When the occupied preheat damper position is closed, the unit
closes the fresh air damper whenever the zone temperature falls
3° F or more below the active heating setpoint. The fresh air damper
remains closed until the zone temperature is within 2° F of the
active heating setpoint.
Using the local fan mode switch to determine the fan operation, the
off position will control the unit fan off close the fresh air damper.
The TUC requires 24 VAC power for proper operation. Wiring
The wiring between the controller outputs and the fresh air damper
must be present and correct for normal damper operation. Refer to
typical unit wiring diagrams on pages 105-106.
If motion detection is enabled and no motion is detected in the
space (by a motion sensor wired to BIP2), the TUC will
apply an alternate fresh air minimum damper position.
Terminal Unit
Control (TUC)
113