APC ACRD101 User Manual

The Proportional plus Integral plus Derivative (PID) loop controls the output of the fans.

Caution: This procedure is to be performed by APC authorized personnel only. Improperly 
set PID controls could result in equipment damage.

There are two sets of PID coefficients stored in the unit. One set is used when the unit is programmed for 
Spot (Proportional) mode and the other set is used when the cooling unit is programmed for InRow 
mode. Only one set can be active at a time. The active PID set is determined by the value of the Type and 
Capacity Ctrl properties (Path: Main > Configure Group). The active set can be read, written or set to 
default.

The proportional multiplier (gain) for this mode or actuator. The proportional multiplier 

adjusts for the difference (error) between the measured value and the setpoint. 

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. 

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. 

(InRow or Spot (Proportional) only)

The Gain, Rate and Derivative coefficients 

return to their default values.