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Thread: Variable speed systems

  1. #1
    CT pump guy Teets's Avatar
    Join Date
    Aug 2007
    Watertown, Connecticut

    Default Variable speed systems

    I have to work on variable speed systems at client's homes as a technician. I have 3 current systems that are experiencing greater than normal pressure drops before the well pumps turn on to build the system back up to pressure. On one a subdrive system I'm experiencing an 8 pound drop. On another a balance flow system I'm experiencing a 10-12 pound drop, should only be 5 psi. On the 3rd a Grundfos Sqe system I'm experiencing a 20 to 40 psi drop before the pump starts, but once it starts it delivers 60 psi consistently until I turn off the flowing water and the it build to 80 psi until it turns off. This system is only set for 60 psi. All 3 systems have tank pressure set at 70% of operating pressure. On the Franklin and Balance flow system I've already changed transducers and moved them to the far side the tank tee's. Same results. What do ya guys think, try new panels or what.

  2. #2
    Porky Cutter,MGWC Porky's Avatar
    Join Date
    Jan 2008
    Virginia Beach, VA

    Default Get away from variable speed pumps!

    Variable speed pumps are a nightmare. Look into a simpler mechanical valve. Cycle Stop Valves Inc. www.cyclestopvalves.com.

    The Cycle Stop Valve can work with your variable speed pump and make it work right. I suggest that you go to their web site, find their 800 # and call them. They can walk you through solving your problem. . . simply.

    Porky, MGWC
    NGWA.org "Master Certified Ground Water Contractor"

  3. #3
    Previous member
    Join Date
    Jul 2009
    North of the Mason dixon Line


    Unfortunately the out lay of cash has no doubt already been made. Where's Valveman with his picture of junk pumps

  4. #4
    Moderator valveman's Avatar
    Join Date
    Mar 2006
    Lubbock, Texas


    The Sub-Drive uses a pressure switch with only 1 PSI between on and off. This should work very fast and not let the pressure drop. Is it possible that the line to this switch is partially blocked?

    The Balance Flow and SQE both use transducers. These take a little longer to react, and added with the slow start built in, the pressure could drop with a high demand before the pump gets up to speed. Could also have a blockage in the line to the transducer.

    These are not the problems I normally here from these type systems. They usually just fail in the on or off position. Failing in the off position means no water. Failing in the on position means extremely high pressure, or the pressure relief valve blowing off water.

    Because these systems are still regulating the pressure, I would say the problem is in the sensor or line to the sensor.

    We started fixing variable speed systems with Cycle Stop Valves almost 20 years ago, and we are still doing it everyday. Newer VFD systems are easier to program or dont require programming but, still have the same problems they have had for more than 20 years. A Cycle Stop Valve and a regular pressure switch will work with those type pumps and will solve the problem. The CSV and regular pressure switch will probably cost less than replacing the pressure transducer.

    Variable Speed Pumps were designed to make money for the manufacturer, not to make the installer look good or save the customer money or energy. As I have said before, you should look at what the pump companies are spending the most money advertising, then do the opposite of that. It takes most installers about 5 years of having problems with VFDs before they start to realize that there is a better way.


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