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NetworkAIR FM DX 60 Hz Operation, Maintenance, and Troubleshooting38
PID controls
Path: Main > Setup > System # > System Config > PID Controls
The Proportional plus Integral plus Derivative (PID) loop is used to control the output of the LiquidCool,
reheat, and dehumidify modes.
Choose which mode or actuator PID loop to tune, using the 01of03: [Mode/Actuator name] setting.
Model. Choose the multipliers to use in the PID algorithm. You can omit the derivative or the integral
and derivative multipliers in the algorithm.
Note: Controllers that use temperature as the process variable calculate the process error in
units of Centigrade.
P. The proportional multiplier (gain) for this mode or actuator. The proportional multiplier adjusts for the
difference (error) between the measurement (temperature or humidity) and the setpoint. The proportional
multiplier is expressed in percent of output per unit of error.
I. The integral multiplier (reset rate) for this mode or actuator. The integral multiplier adjusts for error
measurement and the amount of time that the error has existed. The integral multiplier adds to or
subtracts from the output in small increments to correct for the offset error caused by the proportional
contribution. It is expressed in percent of output for each minute and unit of error (error multiplied by
minutes).
D. The derivative multiplier (derivative) for this mode or actuator. The derivative multiplier adjusts the
output for rapid changes in the error, correcting for the rate of change of the error over time. It is
expressed in percent of output for each unit of error per minute (error divided by minutes).
How to tune the PIDs
A qualified service technician must tune the PID loops to optimize the performance of each mode. The
units shown are for temperature. In the dehumidify loop, the units are in percent relative humidity
(%RH).
Caution: The PID loops must be tuned after the equipment in the room is installed and
running. The loops should be tuned periodically to account for changes in the room load.
1. Select the PID loop to tune.
2. Adjust the integral and derivative constants to zero and the proportional constant to twenty.
3. Set the temperature (cool or reheat) setpoint value and start the System.
4. When the temperature reaches a stable value, increase the proportional constant by 10. If the
temperature does not respond to this change, adjust the setpoint.
5. Repeat step 4 until the temperature value starts to oscillate and the peak amplitude of the
oscillations is constant.
01of03:LiquidCool
Mode: Prop+Int+Der
P: 020 %/°
I: 000 %/°*min
na0432a
D: 000 %/°/min
na0433a