Filter
Top Products
UNT-IOM-6 113
Terminal Unit
Control (TUC)
Table 49. Fresh Air Damper Closed
Probable Cause Explanation
Normal Operation · 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.
Unit Disabled ·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.
Override Present 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.
Latching Diagnostic Present 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.
Autocycle Test 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.
Unit Configuration 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.
Warm-Up Mode 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.
Local Fan Switch: Off 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.
No Power to the TUC 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.
Motion Detection Feature 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.