APC ACRA100 Installation Manual download pdf (Page 36)

Pumped Refrigerant System Operation and Maintenance28

Further tune the PID loop in the following ways to account for changes in the room load:

RDU (component) run hours

The RDU records the number of hours each of its components has operated. When a component is

replaced, use the Reset Run Hours option to reset the run hours for the displayed component to zero.

Path: Main > RDU > Status > Run Hours

Run Hours. View the run hours for the Refrigerations Pumps (1 and 2) and for the DC Power Supplies

(1 and 2).

Reset RDU run hours

Path: Main > RDU > Configuration > Reset Options > Run Hours

Reset Run Hrs. Reset the run hours for the Refrigerations Pumps (1 and 2) and for the DC Power

Supplies (1 and 2) when one of these components is replaced.

CM (component) run hours

Path: Main > Cooling Modules > Select CM > Status > Run Hours

Run Hrs. View the run hours for the fans and fan air filters (RA only of the selected CM).

Reset CM run hours

Path: Main > Cooling Modules > Select CM > Configuration > Reset Run Hours

Reset Run Hrs.

Reset the run hours for the fans and fan air filters (RA only) of the selected CM after

they are replaced.

Thresholds

Set alarms to alert you to threshold violations.

Path: Main > Cooling Modules > Select CM > Configuration > Alarm Threshlds

When the monitored input violates the set temperature threshold of the CM, an alarm will occur. Set

thresholds for the following sensors:

Rack Inlet. The temperature of the air entering the rack at the rack inlet sensor.

Supply Air. The average temperature of the air output from the CM, measured by the supply air

temperature sensors.

Return Air. The temperature of the air entering the CM at the return temperature sensors.

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 ACRA100 Installation Manual Page 36