Terminal Unit
Control (TUC)
96 UNT-IOM-6
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.
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