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Replacing a flow center

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zepfan
zepfan Member Posts: 398
We are going to be replacing the pictured flow center. The pump housing are deteriorated, and leaking. My questions are if the pumps are off and I cut the pvc piping to them should there be any pressure on them? So I can Re glue the new fittings. There are no isolation valves, or a manifold out side where the pipes come in from the ground. Also I assume that I will need to re flush the loop after the new center is installed. Any suggestions would be much appreciated. Thanks to all

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,086
    edited January 2023
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    If there is water in the system above the pumps, then there will be pressure. Is this an open well the pumps are connected to, or is this a closed loop that is in the ground? It does not appear that there are any drain valves on the lower pipe, so there is a water mess on the floor for that pipe. Some closed loops may have Antifreeze in there.

    Do you have any hose bib or boiler drain valves or any type of valve for purging air from the piping? Seems like the original installed elected to go cheep with no unions, valves, or purge ports that might make future servicing a little easier.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    zepfan
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,619
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    You're going to have a mess if you cut that PVC. That looks like a ground source heat pump system with glycol in it. There must be a way to isolate that somehow.

    Can you look inside the flow package and see if there are valves in there?
    zepfan
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,103
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    Nothing more frustrating than valves that SHOULD HAVE BEEN  installed.  Mad Dog 🐕 
    zepfan
  • hot_rod
    hot_rod Member Posts: 22,256
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    PVC is really not rated for glycol.
    We installed CPVC fire protection and used glycerin blend for antifreeze.
    Maybe it is just water, many ground loops are? Much easier to pump and transfer heat with water.

    There are geo specific pumps, either stainless or some have a resin coated volute to combat corrosion.

    It’s a tough life for those high head circs if that is a non pressurized system. No NPSHa causes them to cavitate sometimes, so you can get both corrosion and erosion of the circulators😗

    There may be a single pump option now, instead of that push pull pump arrangement . I see pumps like the Grundfos Magnas on geo loop fields

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    zepfan
  • zepfan
    zepfan Member Posts: 398
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    The new flow center looks identical to the one that is in the picture. There is an isolation valve built into the center, but that won't help when the whole unit is being removed. I have traced the pipe back to where it comes through the wall and there is no isolation valves, unions, or hose bibs. The only connection/access port is a pete's plug fitting at the unit. That is all. From what I can tell the system in a closed loop that goes in the ground. Thanks to all that responded
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,619
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    looks like you have to drain the whole works. Does it contain glycol?
  • zepfan
    zepfan Member Posts: 398
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    The fluid we are having it tested to determine what it is. It is not pure water, but doesn't look or smell like either type of glycol. Once the test is back I will re post. The agency that we use for water treatment tests, doesn't charge for testing but they take their time. Normally 10-14 days
  • Derheatmeister
    Derheatmeister Member Posts: 1,549
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    This Push/Pull Pump station looks just like the ones from Waterfurnace... You may be able to just isolate and change the pumps (Grundfos 26-99 ) from the field with the purge point 3 way valves that are on it !
    If you are planning on draining the fluid to perform repairs you MAY not be able to reinstall the fluid using a regular Glycol pump..Some Geo fields need to be purged with high velocity pumps in order to remove the air from the field.
    zepfan
  • Derheatmeister
    Derheatmeister Member Posts: 1,549
    edited January 2023
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    After a closer look the valves are allready in the "Service" position...
    From here i would:
    1.Relief the pressure into a bucket.
    2.Change both circs. Use Stainless Steel from now on !
    3.Reinstall the Fluid with a regular Glycol pump.
    4.Open the valves back to the Geo field.
    5.Recommission the System.
    Done...
    Address System fluid when the results come back.
    If your Glycol is deteriorated i would not leave this system off since it may freeze the geo loops causing extensive damage !!
    Hope this helps. :)
  • hot_rod
    hot_rod Member Posts: 22,256
    edited January 2023
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    Different types of alcohol were used as geo fluids. Although most circulator manufacturers do not approve their pumps for that fluid.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    zepfan
  • zepfan
    zepfan Member Posts: 398
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    Thanks for the responses. Unfortunately the service valves on the flow center are not going to help in this instance, as the whole flow center needs replacement. I plan on pumping out the residual fluid with a standard transfer pump, and am assuming that I will need a flush cart to put it back in. Seeing how this loop serves two units would it be wise to install pvc isolation valves ahead of the flow center, or is that just going to add cost, and pressure drop for the loop? Otherwise put it back together as it was originally installed?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,619
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    If you have to drain it putting in a couple of valves is a good idea. Maybe a couple of tees below the valves to purge and drain the geo loop
    mattmia2
  • Derheatmeister
    Derheatmeister Member Posts: 1,549
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    zepfan said:

    Thanks for the responses. Unfortunately the service valves on the flow center are not going to help in this instance, as the whole flow center needs replacement. I plan on pumping out the residual fluid with a standard transfer pump, and am assuming that I will need a flush cart to put it back in. Seeing how this loop serves two units would it be wise to install pvc isolation valves ahead of the flow center, or is that just going to add cost, and pressure drop for the loop? Otherwise put it back together as it was originally installed?

    Why can you not just change both of the pumps vs changing the entire Pump station/ flow center ?
  • hot_rod
    hot_rod Member Posts: 22,256
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    The Grundfos Geo Magna is a 9-182w pump that you can vary the speed.


    Those two 116’s are 377w each, 754w!

    Seems like a nice upgrade for performance and energy consumption
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Derheatmeister
  • zepfan
    zepfan Member Posts: 398
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    We did just get the fluid test results back and it does not appear that this fluid contains any glycol. It shows a freeze point of 31, ph level of 4.9. The report does not mentioned specifically what the fluid is other then to state "use of non purified water has been detected". Any suggestions as to what this fluid is would be much appreciated. As I mentioned before the fluid is clear, has a glycol residue to it, but is not glycol. I don't know if the high freeze point is a concern as all the piping for the system seems to be below the freeze level of the ground. Thanks to all
  • hot_rod
    hot_rod Member Posts: 22,256
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    As I suggested above, you cannot put glycol in PVC, so the clear fluids are usually either an ethanol or methanol geo fluid.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    zepfan
  • leonz
    leonz Member Posts: 1,159
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    UGH!!!!!!!!!!!!!!!!!!

    It plainly obvious to me whoever installed it just installed it and did not add anything to enable the next
    person to work on the system.

    You need a pair of PVC tapping saddles placed under the service center after the bottom elbows to connect 2 drain hoses to empty the system.

    It is time to cut that mess out of there and replumb it the right way.

    If you have time to order a half dozen 15 gallon poly barrels I would do that before your drain it tapping into the PVC and using a garden hose to drain into the drain pan that has the drain that fits in the large barrel bung of the fifteen-gallon barrel.

    Adding back cpvc boiler drains with caps to the system in combination with cpvc shut off valves on both sides of each valve in the bottom pipe runs are a must in my opinion.


    zepfan