Terminal Unit
Control (TUC)
Table 49. Fresh Air Damper Closed
Probable Cause | Explanation |
Normal Operation | · The |
| during occupied mode and closes during unoccupied mode. |
| · Modulating analog and |
| 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 |
| 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. |
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 |
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. |
113 |
