AHU - VFD Operation

AHU - VFD Operation

Testing Procedure

Pre-Conditions Check

Before testing is started, it must be verified that the AHU is running.
  • Verify that device is “Occupied”.
  • Verify fan is running by checking that duct pressure is more than 0.4psi [Pressure Min Threshold]
If this condition is not met, STOP the workflow and ARCHIVE.

Setup Testing Conditions

In order to ensure that testing is accurate, first check to make sure that the AHU is currently maintaining pressure as directed by its setpoint. If not, then the test will be aborted.
  • Verify that duct static pressure sensor is within 5% [Relative Tolerance] of setpoint.

Testing VFD Response

Raise Duct Static Setpoint
  • Command static pressure setpoint to 20% [Relative Modulation] above setpoint
  • Pass if static pressure sensor reads within 5% [Relative Tolerance] of setpoint
Lower Duct Static Setpoint
  • Command static pressure setpoint to 20% [Relative Modulation] below setpoint
  • Pass if static pressure sensor reads within 5% [Relative Tolerance] of setpoint

Tuning Parameters

DisplayHint
Relative Modulation [20%]How much do we want to change the setpoint from the current one in percentage.
Relative Tolerance [5%]How much do we tolerate the difference between sensor and setpoint in % after the change to be able to say that the test has been succesful.
Nominal Tolerance [0.1psi]How much do we tolerate the difference between sensor and setpoint after the change to be able to say that the test has been successful.
Pressure Min Threshold [0.4psi]How much should the duct pressure be minimally.
Reaction Time [300sec]How long to wait for the actuators to fully do their job.
Stabilization Time [60sec]How long to wait for the system to come to stability after we have given it an actuator command and the conditions have been fullfiled.
Measure After [60sec]How long to wait in seconds to start checking the feedback readings.

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