Liebert TM-10098 service manual iCOM Controls Training and Service Manual

iCOM Controls Training and Service Manual

A suggested tuning procedure is as follows:

1.Initially adjust the integral and derivative settings to 0% / degree-min and 0% / degree / min..

2.Starting with 20% / degree, adjust the proportional setting in small increments (10% steps) until the control sustains a constant hunting action (the temperature swings are approximately the same amplitude from one peak to the next).

3.Note the time in minutes between peaks of adjacent temperature swings and the amplitude of the temperature swing (degrees above the set point).

4.Adjust the proportional control setting to about l/2 the value obtained in Step 2.

5.Adjust the integral setting to a value calculated by the following equation: approximate room load (in % full load) time between peaks x peak amplitude x 4.

Note: If calculation results in a value of less than 1%, then set the integral to 1%.

6.Adjust the derivative to a value calculated by the following equation: time between peaks x 5%.

The above tuning procedure is only an approximation for an initial set of adjustments and are based on the "average" room characteristics. Your particular settings may need to be further adjusted for optimum PID control performance.

Some suggestions for additional tuning are as follows:

•If cooling output overshoot is occurring on load changes, decrease the proportional setting or the derivative setting.

•If system hunting occurs with constant room load, decrease the integral setting.

•If the control responds too slowly, resulting in large temperature excursions on a load change, increase the proportional setting or the derivative setting.

•If a constant temperature deviation exists between the temperature and set point, increase the integral setting.

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