VFD EAGLE – Setting the Relief Valve

The Relief valve on a VFD Eagle pumping system is important to the protection of the irrigation piping.

Normally, the valve will open as the system pressure rises 15-20 psi above the “Normal Mode Setpoint.” Once open, it should control the system pressure within a range of 10-15psi above the “Normal Mode Set Point.”

The procedure to set the relief valve is as follows:

1) Remove the lock nut from the speed control and turn the screw in (clockwise) until it bottoms out. Depending on the size of the valve typically 3″, 4″ or 6″, the adjusting screw should be turned out 11/2, 2 or 3 turns respectively.

2) The control pilot, CRL, should be turned in until no more than 3/4″ of threads are exposed. Use a correctly sized wrench to perform this adjustment and turn the screw slowly to avoid damaging the threads.

3) Close the station discharge isolation valve.

4) Turn on the pressure maintenance pump in the “hand” position.

5) Slowly unscrew the CRL adjusting screw until the valve opens and continue until the pressure indicated on the OIT is 12psi over the “Normal Mode Setpoint.” Tighten the lock nuts.

6) Close the ball valve on the downstream side of the CRL forcing the relief valve closed. Once the pressure has risen to a high system condition, open the ball valve and confirm that the relief valve opens to once again reduce the system pressure.

The relief valve is now set “more or less” as it needs to be, however fine tuning will need to be performed with the entire irrigation system connected to the pump station. This is performed as follows:

1) With the VFD operational, place one main pump in the “Hand” position with no flow demand in the field.

2) Using the OIT, press “speed control,” press “Toggle.” The pump that is running is now in “Manual Speed Control.”

3) Cursor right and increase the speed to 100%. Monitor the pressure and relief valve operation. It should rise as it did with the PM pump and open at or abut the system High Pressure Alarm Setpoint. The pressure should then reduce to approximately 12 psi above “Normal Setpoint.”

4) Adjust the CRL until this pressure is attained

5) Lower the pump speed until the valve closes being sure that it does before reaching “Normal Setpoint.”

6) Increase the speed manually again until the valve opens then reduce it until it closes. The operation should be repeatable.

7) Small adjustments of the speed control and/or CRL may be necessary to fine tune the valve’s response. Make small adjustments slowly. Do not become frustrated at the valve response drifts. Go back to the original speed control and CRL setting if necessary and try again.

All irrigation systems are different. Elevation changes, various piping configurations and pressure control devices will cause different operation of the system relief valves. If proper control cannot be attained and all components are clean and functional, call SyncroFlo Technical Service for assistance.