APC ACRA100 Installation Manual download pdf (Page 35)

27Pumped Refrigerant System Operation and Maintenance

Tune the PID loop

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

Note: The PID 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.

NOTICE

HAZARD TO EQUIPMENT

This procedure is to be performed by APC authorized personnel only. The PID loop must

be tuned after the equipment in the room is installed and running.

Failure to follow these instructions can result in equipment damage.

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

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 67 68

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APC ACRA100 Installation Manual Page 35