See Disabling PRAC+ Loop Tuning for how to disable adaptive tuning and use manual tuning. With manual tuning, a loop is considered well tuned if it comes within setpoint by the minimum tune band within 60 samples.
When you attempt to manually tune a loop, make sure to check if another control loop is causing a cascading effect on the loop you want to tune. If the mixed dampers are cycling wildly, you should not try to tune the cooling valve. Start at the beginning of a mechanical system and work towards the end to keep things simple.
Verifying that hot water temperature and pressure are stable also makes tuning a heating loop much easier. Again, start with the heating/cooling plant, using it as the source energy for a control loop, and ensure things are stable before attempting to tune.
Table 1 provides a manual tuning checklist.
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Step |
Completed |
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If tuning problems have been identified using trend data, use the Tuning Reset command to reset the parameters to the factory-default tuning parameters. See Resetting Tuning Parameters for procedures. Allow the system to stabilize for at least four times the time constant after resetting the parameters. For example, wait 60 minutes for zone control (4 x 15 min.) and approximately 2 minutes for discharge air temperature control (4 x 30 s) |
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If tuning problems persist, review the Process ID selection and consider using a faster or slower Process ID for this PID loop. See Table 1 for a list of Process IDs. |
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If tuning problems continue, perform a step test. Manually tune the PID using the calculated parameters from the step test. See Performing a Step Test for procedures. |
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If tuning problems continue, manually tune the PID using the instructions in the Disabling PRAC+ Loop Tuning section. |