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1. All fans assigned to a fan group will turn on once the room temperature rises above the ACTIVATION
TEMPERATURE. The default activation temperature is 75°F or 25°C.
2. The fans will start at low speed (15 Hz or 27% minimum). The low speed for each fan group is
configurable.
3. As the temperature rises in the building, the fan speed will increase until the temperature reaches the
end of the MODULATION BAND. The modulation band default is 5°F or 3°C and is adjustable. In the
default case, at 80°F or 28°C (activation temp + modulation band), the fan will be at its maximum
speed (55 Hz (HVLS) / 80 Hz (Vent) or 100%). The maximum speed for each fan group is configurable.
4. As the temperature decreases, the speed will decrease until the temperature falls back down to the
activation temperature. At this point, the fans will be back at minimum speed.
5. As the temperature decreases below the activation temperature, the fans will continue to operate at
their minimum speed until the temperature falls below the HYSTERESIS temperature. The hysteresis
temperature default is 1°F or 0.5°C. In the default case, below 74°F or 24.5°C (activation temp -
hysteresis temp), the fan will stop and will stay off until the temperature rises back above the activation
temperature.
6. There is also a MINIMUM cycle timer in the system to help prevent frequent fan cycling. The default
setting is 30 minutes. Once the fans start, the fans will run for at least this amount of time before
turning back off.
Figure 36 - Fan Cycle
NOTE: All fans assigned to a group will follow the average temperatures defined for that group.
They will also follow the min and max VFD speeds assigned to that group. The Activation
Temperature, Modulation Band, and Hysteresis Timers are dependent on the Low and High Alarm
Temperature Limits. Sometimes the adjustment range is limited to prevent overlap with the Alarms.
Table 6 - Automatic Mode Operation Summary
Monitoring Points Units Configurable Item Range/Limit
Power Kw Min Speed 15 Hz to Max
Current Amps Max Speed
Min Speed to
55 Hz (HVLS)/80 Hz (Vent)
Speed Hz Activation Temperature 40-100°F (5.5-38°C)
Motor Voltage Volts Modulation Band 1-15°F (0.5-7°C)
% Load % Hysteresis Temperature 0.5-20°F (0.5-11°C)
Run Time Hours Min Cycle Timer 1-60 Minutes
VFD Temp °F/°C Temperature Units °F/°C
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