Another Grundfos Cu301 issue

[ajcook]

I see lots of good advice on your forum about the Cu301 system, which I have. The controller is in the basement and the pump is in a 35ft well; not sure which pump model. The system (set at 70psi) is ~14 years old with no issues until this irrigation season. The irrigation system is set to run starting at 4am and finish around 7:30am when no other appreciable demand is on the pump. After running for an hour or so, the system would shut off for a few seconds and kick back on and run for another minute or so and repeat. The "shutting off" makes a loud enough knocking noise to wake us up and keep my wife up. The Cu301 was showing the pump overspeed light and the maintenance light during the shut off but both disappeared quickly and the system started up again... rinse & repeat. The Grundfos manual suggests the Maintenace light should stay on once tripped. I checked the pre-charge tank and it was a little low so I charged it up to 59psi (I know it is supposed to be 49psi but I was going from bad memory on the pre-charge setting for 70psi). Then, the lights showed the overvoltage light and the Maintenance light with the same performance of run for an hour so just fine and then cycling off and on. I set the system pressure to 50psi and the off/on cycling stopped but the water pressure in the sinks and shower pulses slightly.
I am going to check the pressure valve for rust fouling and set the pre-charge to the proper setting while the system is down and relieved of pressure.
I like the idea of the CSV set up you recommend but I'm concerned if the issue might still be the pump.

 

[ajcook]

I see lots of good advice on your forum about the Cu301 system, which I have. The controller is in the basement and the pump is in a 35ft well; not sure which pump model. The system (set at 70psi) is ~14 years old with no issues until this irrigation season. The irrigation system is set to run starting at 4am and finish around 7:30am when no other appreciable demand is on the pump. After running for an hour or so, the system would shut off for a few seconds and kick back on and run for another minute or so and repeat. The "shutting off" makes a loud enough knocking noise to wake us up and keep my wife up. The Cu301 was showing the pump overspeed light and the maintenance light during the shut off but both disappeared quickly and the system started up again... rinse & repeat. The Grundfos manual suggests the Maintenace light should stay on once tripped. I checked the pre-charge tank and it was a little low so I charged it up to 59psi (I know it is supposed to be 49psi but I was going from bad memory on the pre-charge setting for 70psi). Then, the lights showed the overvoltage light and the Maintenance light with the same performance of run for an hour so just fine and then cycling off and on. I set the system pressure to 50psi and the off/on cycling stopped but the water pressure in the sinks and shower pulses slightly.
I am going to check the pressure valve for rust fouling and set the pre-charge to the proper setting while the system is down and relieved of pressure.
I like the idea of the CSV set up you recommend but I'm concerned if the issue might still be the pump.

 

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[Valveman]

Sorry I missed this. Most likely the problem is with the CU301 controller, not the pump. It is a default setting to cycle on and off when the CU301 looses contact with the motor. I would recommend a 10 gallon size tank with the CSV1A set for 70 PSI using a heavy duty 60/80 pressure switch as can be found in the PK1A kit here.

PK1A Pside-Kick Pressure Tank Kit – Cycle Stop Valves, Inc

Buy It! Interactive Animation Installation Video General Information Typical Applications Specifications Dimensions Installation Instructions Troubleshooting VFD Controller Replacement WARNING: This product can expose you to chemicals including nickel, which is known to the State of California...

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