Data Aire gForce Ultra - Fan Speed Modulation Proportional to Cooling Demand (Mod to Comp); Fan Speed Modulation to Return Air (RA) Temperature (Mod to Rett); Fan Speed Modulation to Constant Static Pressure (Air Pressure); Fan Speed Modulation Based on BMS (BMS Speed)

10-2014 gForce User Manual ● 101
9.1.2 Fan Speed Modulation Proportional to Cooling Demand (Mod to Comp):
Proportional fan speed control is based on the cooling demand. The fan speed ranges
from 70% to 100% of fans total capacity. When the fans start, they operate at the
minimum fan speed. As the compressor modulates from minimum to maximum speed,
the fan speed will modulate proportionally to the compressor VFD between the
minimum fan speed to the maximum fan speed. The fans will operate at the maximum
fan speed when reheat or humidification is required.
9.1.3 Fan Speed Modulation to Return Air (RA) Temperature (Mod to RetT):
The dap4™ controller is set for fan speed control based on Return Air (RA)
temperature. As the RA temperature rises, the fan will start at the minimum speed and
increase by 10% for every 0.1⁰F above RA Temp setpoint plus RA Temp deadband.
9.1.4 Fan Speed Modulation to Constant Static Pressure (Air Pressure):
In the Constant Static Pressure Control mode, the fan proportionally increases or
decreases the speed to maintain a constant static pressure set-point in the controlled
space.
NOTE: This feature requires an optional differential pressure transmitter to
measure and control the static pressure of the controlled space.
9.1.5 Fan Speed Modulation based on BMS (BMS Speed):
In this mode, the controller allows the BMS to change the constant fan speed mode of
the fans from 70% to 100%. The fans will run at a constant speed in this mode. When
the fans start, they will operate at the front panel’s programmed constant fan speed
then it will modulate to the BMS programmed fan speed when a network
communication with a BMS is established.
If the reheat or humidifier is required, the maximum fan speed setting is used. If reheat
or humidifier is required while the fan speed is commanded by the BMS to a value that
is lower than the maximum fan speed, the fan speed will automatically increase to the
maximum speed. The fan speed will revert to the BMS programmed fan speed when
reheat or humidification is no longer needed.