Trane LO manual Terminal Unit Control TUC, UNT-IOM-6

Terminal Unit

Control (TUC)

the outside air temperature falls to 10° F or more below the zone temperature. The TUC will control the damper to a position to produce optimal cooling during economizing. If power is interrupted or the TUC is turned off, the damper will spring back to the closed position.

If the occupied preheat damper position is configured as closed (the factory configures as open), the fresh air damper remains closed during the transition from unoccupied mode to occupied mode until the zone temperature is within 2° F of the heating setpoint (warm-up sequence), or cooling setpoint (cool-down sequence). During the warm-up sequence, the damper fully closes, the fan operates on high speed, and the heating valve drives fully open to until the zone temperature approaches the occupied heating setpoint. If the zone temperature falls 3° F or more below the heating setpoint during the occupied mode, the TUC reinitiates the warm-up sequence until the zone temperature is within 2° F of the heating setpoint.

If during the occupied heating mode, the TUC determines that no heating capacity is present and the zone temperature drops 3° F below the heating setpoint, the TUC closes the fresh air damper regardless of the occupied preheat damper position. The cool-down sequence has a maximum duration of one hour and cannot be reinitiated once the unit is in occupied mode.

All units ship from the factory with the damper in the closed position.

Note: The open position of the damper does not correspond to the amount of fresh air provided to the unit. It is the installer’s responsi- bility to ensure that the building’s minimum fresh air requirements are met while taking the necessary freeze conditon precautions to protect the unit.

96 UNT-IOM-6