American Standard UV05 User's Manual | Page 31

American Standard Air Conditioners User's Manual - UV05.
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McQuay OM 751

31

Description of Operation

In general, it is best to start with a relatively large proportional band setting (the factory 
default setting is best) and adjust to smaller values.

If you want the system to respond strongly to small changes in the space, adjust the 
proportional band to a higher setting.

If you want the system to react weakly to small changes in the space, adjust the proportional 
band to a higher setting.

Integral Time

The integral time, or integral action, causes the controlled output to change in proportion 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 22). The integral action 
works to reduce this “area under the curve” and to eliminate any natural system offset.

Figure 22: Integral time

The smaller the integral time, the faster the output ramps up or down with small changes 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 22).

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 occupancy 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 maintains 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.

Area Under The Curve

Too Small

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