Vertiv Liebert iCOM DP400/500, Installer/User Manual

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Figure 3.2 Temperature Control with a Deadband
No. Description
1 ½ of proportional band.
2 ½ of proportional band.
3 Deadband.
Considerations when Using PI Temperature Control
Several factors, such as room heat load, external heat gains, and component specific performance can affect the PI control
loop. Adjusting the temperature proportional band and integration time can improve cooling unit performance and avoid
problems detailed in Table 3.1 below.
Problem Solution
Cooling is slow to activate
Decrease the proportional band slightly and monitor operation.
Repeat until cooling-reaction time is acceptable.
Compressor short-cycle alarm
Increase the proportional band slightly by increasing the integration time between 3 and 5 minutes, and monitor
compressor run time.
Set the temperature deadband to 2.
Run time must be more than 3 minutes to prevent a short-cycle of the compressor.
Excessive valve oscillation or
hunting
Increase the proportional band and/or increase integration time.
Table 3.1 PI Temperature Control Troubleshooting
3.1.4 Compressor Control by Cooling Requirement
Compressor control is directly linked to temperature control in that the cooling requirement determined by the
temperature proportional band determines compressor operation. Depending on the type of cooling unit, the number and
type of compressors varies. The following describes compressor operation along the proportional band for the varying
compressor options.
3 Service Operation
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