Fan Mode Operation
Terminal Unit
Control (TUC)
high or low temperatures. In addition, the TUC calculates the heating setpoint equal to the cooling setpoint minus an adjustable heating offset. Furthermore, the heating setpoint cannot exceed a value less than or equal to the cooling setpoint. The TUC is in the cooling mode when the space temperature rises 1° F above the cooling setpoint. The TUC is in the heating mode when the space temperature drops 1° F below the heating setpoint. The unoccupied setpoints are typically widened to account for night setback and are adjustable with either Tracer® or EveryWareä software.
Off Position
On a
High, Medium, or Low Postion
With the fan mode switch in the high, medium, or low position; the fresh air damper option and the control valve(s) operate to maintain setpoint.
Auto Position
As the capacity requirement increases at low fan speed, the control valve gradually opens. The fan speed increases to medium after reaching the low speed capacity switch point. This causes the control valve to reposition to maintain capacity, gradually opening as demand increases. The fan speed increases to high after reaching the medium speed capacity switch point. This causes the control valve to reposi- tion to maintain output capacity, gradually opening as demand increases. As capacity decreases, the control valve closes until reaching the fan switch point. After reaching the fan switch point, the fan speed decreases to medium with the control valve repositioning to maintain constant capacity. As capacity decreases, the control valve closes until reaching the fan switch point. After reaching the fan switch point, the fan speed decreases to low with the control valve repositioning to maintain constant capacity. At low speed, the control valve closes incrementally as demand decreases.
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