Variable speed systems

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by Teets, Oct 16, 2009.

  1. Teets

    Teets CT pump guy

    Aug 23, 2007
    well tech
    Watertown, Connecticut
    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. masterpumpman

    masterpumpman New Member

    Mar 26, 2007
    Consult and Teach Well Drilling Internationally
    Virginia Beach, VA
    Get away from variable speed pumps!

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

    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 "Master Certified Ground Water Contractor"
  3. Sponsor

    Sponsor Paid Advertisement

  4. nhmaster

    nhmaster Master Plumber

    Jul 30, 2008
    Tech. Instructor
    S. Maine
    Unfortunately the out lay of cash has no doubt already been made. Where's Valveman with his picture of junk pumps :D
  5. valveman

    valveman Cary Austin Staff Member

    Mar 15, 2006
    Pump Controls Technician
    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 don’t 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 VFD’s before they start to realize that there is a better way.
Similar Threads: Variable speed
Forum Title Date
Pumps and Tanks Well Forum & Blog. Water is life. Grundfos Variable Speed Well Pump Failure Aug 29, 2016
Pumps and Tanks Well Forum & Blog. Water is life. variable speed well pump to ditch tank? Feb 28, 2016
Pumps and Tanks Well Forum & Blog. Water is life. Variable Speed/Flow pumps and energy usage Feb 18, 2010
Pumps and Tanks Well Forum & Blog. Water is life. Bladder Tank Sizing for Variable Speed Pump Dec 4, 2009
Pumps and Tanks Well Forum & Blog. Water is life. Goulds constant press & variable speed pumps May 23, 2008

Share This Page