Replacing Grundfos Pump in Flow Controller

Discussion in 'Surface Water Loops' started by QAS, Aug 29, 2011.

  1. QAS

    QAS New Member

    I believe that I have a defective pump in my flow controller. The pump itself is noisy. It does work and I do have flow, but it is making a loud whining sound on some cycles, but not on all cycles. We did have air in the system first which had its own distinct sound and had to have the contractor come out to re-flush the loop. To replace the Grundfos pump, do I need to have the loop re-flushed or can I just replace the pump itself without introducing air to the system?
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Is your system a pressurised system or non-pressurised? Is your system horizontal or vertical?

    A horizantol non pressurised system should fair well with a diy pump replacement. The other not so much, it will need to be purged.
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    Pebbles and such can cause noise.
  4. QAS

    QAS New Member

    We have surface loop in a pond, it is a pressurized flow controller. If we break into the system to install the pump, I'm afraid I won't be able to re-pressurize the system properly. Haven't found much info on how to replace just the pump instead of the whole flow center.
  5. Looby

    Looby Member Forum Leader

    A "flow center" is just a pump (or two) and a pair of 3-way
    valves designed to isolate the heat pump from the loop.
    It should be no problem to replace the pump(s) without
    getting air in the loop. After the swap, you'll have to bleed
    air from the flow center (and maybe the heat exchanger
    and hose kit), but that shouldn't require a purge cart.

    After that, you can re-pressurize the loop through one
    of the P/T ports -- with nothing more than a basketball
    inflation needle, and your domestic water supply.

    Find the flow center manual online. Read it. If that's not
    enough to answer your questions, hire a pro.

    But FIRST, make sure that the pump is actually defective.
  6. QAS

    QAS New Member

    I haven't been able to find any info on this in my installation manual for the flow controller attached. Anybody else have any more detailed info on how to replace just the pump?
  7. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    First determine pump is bad vs air in system or debris. If you do not have tools to check loop pressure and antifreeze efficacy, you are not equipped to change pump.

    A flow center has three way valves as was said.
    If you know where those are (generally on both upper sides of assembly) look inside at the round plate. There should be a 3/8 square hole for a socket wrench extension to turn the valve and some sort of "T" etched in the plate to indicate valve position.

    Look at theat "T" and compare the position of each of it's 3 arms to an opening: service port. The "T" should currently be on it's side with the base pointing at the wall (or whatever surface your flow center is mounted on). This tells you that you are open to the loop field and the hose kit but not the service ports.

    I use adapted boiler drains and garden hoses for this sort of repair. Once my valves are installed on the flow center I turn the valves so that the "T" (generally) is right side up indicating closed to the loop field but open to service ports and hose kit/heatpump.
    After making changes, you can use a run water through one service port and open the other to a drain (follow direction of flow arrows on flowcenter or heat pump). Push water through 'til air is forced out. Close discharge side to pressurize.

    Open to loop field and fill to desired pressure. Run flow center for some time (15-20 minutes) then test antifreeze protection. Turn 3 way valves to isolate service ports and remove your repair kit.

    Goofing up any part of the sequence could discharge brine into mechanical room, de-pressurize or even introduce air into loops. Every time you get into the loops you dilute antifreeze as well. So if you try and fail, make sure you get a pro to do a flush for ya and know that you at least saved money on pump mark-up and labor.

    Good Luck,

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