Instruction manual
OM 751-4 30 www.DaikinApplied.com
desCrIptIon of operatIon
Integral Time
The integral time, or integral action, causes the controlled output to change in propor-
tion to time difference between the sensor value and set point. The difference over time
between the actual value and set point forms an “area under the curve” (see Figure
20). The integral action works to reduce this “area under the curve” and to eliminate
any natural system offset.
Figure 20: Integral time
Area Under The Curve Too Small
The smaller the integral time, the faster the output ramps up or down with small chang-
es in the space. The smaller the integral time, the quicker the system reacts to small
changes in the space. If the Integral Time is set too small, long oscillations occur (see
Figure 20).
In general, it is best to start with a relatively large integral time setting (the factory default
setting is best) and adjust to smaller values. If you want the system respond strongly
to small changes in the space, lower the integral time. If you want the system to react
weakly to small changes in the space, adjust the integral time to a higher setting.
Indoor Air Fan Operation
The UVC supports a three-speed indoor air (IA) fan; low, medium, and high. The UVC
calculates the effective fan speed and operation based on the unit mode, the occupan-
cy mode, and the values of several network variables.
Auto Mode
The UVC is provided with a user selectable auto fan mode feature. When in auto fan
mode, the UVC uses the space temperature PI loop to automatically adjust the fan
speed as needed to maintain space temperature. This ensures that the UVC main-
tains the lowest and quietest fan speeds whenever possible. When in auto fan mode,
a maximum of six fan speed changes per hour is allowed (by default). This prevents
frequent automatic fan speed changes from disturbing room occupants.
Occupied, Standby, and Bypass Operation
During occupied standby and bypass modes, the IA fan, by default, remains On.
Unoccupied Operation
During unoccupied mode, the IA fan typically remains off and cycles with calls for heat-
ing and cooling.
Cycle Fan
The UVC is provided with a Fan Cycling Conguration variable that can be used to
force the IA fan to cycle with calls for heating and cooling during the occupied, standby,
and bypass occupancy modes. When the fan is off, the OA damper is closed. Daikin
recommends using this feature only when it is acceptable that normal ventilation is not
required.
When the IA fan is set to cycle, the UVC is congured to continue fan operation for a
time period after heating or cooling is complete.