APC ACRC500 Manuel d'installation télécharger pdf (Page 24)

InRow RC Operation and Maintenance16

Tune the PID loop

Tune the PID loop to optimize the performance of the cooling group.

Caution: This procedure must be performed by APC authorized personnel only. The PID

loop must be tuned after the equipment in the room is installed and running. The loop should

be tuned periodically to account for changes in the room load.

1.Adjust the integral and derivative constants to zero and the proportional constant to 1.0.

2. Set the temperature setpoint value and start the cooling group.

3. When the temperature reaches a stable value, increase the proportional constant by 0.5. If the

temperature does not respond to this change, adjust the setpoint.

4. Repeat step 3 until the temperature value starts to oscillate and the peak amplitude of the

oscillations is constant.

5. Note the time, in minutes, between the peaks of the oscillations. This is the Ultimate Period, P

6. Note the value of the proportional constant. This is the Ultimate Gain, G

7. Compute the PID constants using the table below. Use the equations for that control method in

the row to compute the values for each constant.

8. Set each constant according to these calculations.

You may need to further tune the PID loop in the following ways to account for changes in the room

load:

Control Method Proportional Integral Derivative

P 0.5*G

––

P + I 0.45*G

0.54*G

–

P + I + D 0.6*G

1.2*G

0.075*G

Loop Behavior PID Tuning Correction

Slow response to temperature changes Increase the proportional multiplier or increase the

derivative multiplier.

Overcooling/undercooling after changes in the room

load or changes in setpoint

Increase the derivative or the proportional multiplier.

Environmental temperature never reaches the

setpoint

Increase the integral multiplier.

Overcooling/undercooling on constant room load Decrease the integral multiplier.

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APC ACRC500 Manuel d'installation Page 24