Help me interpret pump changes

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by leeelson, Aug 7, 2018.

  1. leeelson

    leeelson Member

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    Dec 12, 2009
    Location:
    Nevada
    Grundfos 25S20-11 2HP installed in Feb '16 with CSV 125 60-1. I have a cycle sensor that gives current draw. When the pump was installed, the max current draw was about 9 amps but only when running my largest irrigation line. Most lines showed about 8 amps. I believe that the largest current draw possible is about 11 amps. Over the past 6 months, I've noticed the current draws are rising with no changes in the irrigation system that I know of. Now, most lines max out at 11 amps, and there is (an expected) concurrent drop in pressure. From my understanding, if a pump motor is working properly, current draw is simply a function of GPM, so it's hard to understand the current increase unless the pump is (slowly) dying. I don't believe that TDH (higher in summer?) should have an effect. I have yet to try a fill test. Any insights into what is going on?
     
  2. valveman

    valveman Cary Austin Staff Member

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    Same pump and CSV I have at my house, which hasn't been touched in at least ten years. You might check the run capacitor in the control box. A bad cap means low voltage and higher amperage. Also check the incoming voltage for the same reason. However, I am afraid you may have a thrust bearing problem. If the pump is set in the well where the water enters from above the pump, the thrust bearing at the bottom end of the motor could be getting hot. All pumps need to be set above where the water comes into the well, or they need a cooling shroud/flow inducer sleeve.
    shroud 3 pics.jpg
     
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  4. leeelson

    leeelson Member

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    Thanks. Any suggestion as to how to test the capacitor? I have volt/amp meter (clamp). Line voltage in is 220. Voltage to motor is 330. Sound right?
     
    Last edited: Aug 7, 2018
  5. Reach4

    Reach4 Well-Known Member

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    To test a run capacitor for gross failure, you need to lift the wires off of one side. Use the highest range on your ohmmeter. When you first attach the meter, expect to jump low, and then rise to infinity. Reverse the leads, and it will jump lower still again, and rise to infinity.

    The ohmmeters vary a lot in how much current they put out while measuring resistance, so the degree of jumping down will vary. There are meters that actually have a capacitance measuring function. If you have a friend who does much in electronics, you might be able to borrow one.
     
  6. valveman

    valveman Cary Austin Staff Member

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    Or just get a new capacitor and check the amps. :)
     
  7. leeelson

    leeelson Member

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    Found a capacitance checker. Run capacitor is 17.2 microF. Sound about right? I have no wiring diagram other than the cover. Relay checks out OK.
     
  8. Reach4

    Reach4 Well-Known Member

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    20 uF (MFD) is nominal, so sounds about right. 14% below nominal... I am not sure what the tolerance should be, but the meter could be a tad off too.
     
  9. leeelson

    leeelson Member

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    Talked to Grundfos tech support. They confirm 20 MFD and say that max output for pump is 13 amps (this is for more than the rated 2 hp) and not to worry. I'm not convinced and am pretty discouraged at the thought of being without water during summer if the pump fails, especially after 2.5 years of life. I bought the pump, motor and control and had a lot of trouble getting an installer to install it. I'm not too happy with buying another Grundfos pump and all the local installers don't like the small pressure tank and CSV.
     
  10. leeelson

    leeelson Member

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    If the thrust bearings are heating up, wouldn't I expect to see current increasing over time? I have 2 hour run times for irrigation and don't see this kind of behavior. In summer, typical total run times are about 2-3 hours per day, with no cycling thanks to the CSV. Is this excessive for a pump?
     
  11. valveman

    valveman Cary Austin Staff Member

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    Pumps are made to run continuously. I have a Grundfos on a stock water well that hasn't shut off in 17 years. Running 2 hours at a time is good for the pump. Cycling on and off several times in 2 hours would be bad. There is nothing wrong with Grundfos pumps. However, I am hearing of a few problems lately with Grundfos motors.

    If the thrust bearing is going out the amps will increase as the flow decreases. In other words when the CSV restricts the flow to fill the tank at 1 GPM, the amps should drop by 50% from full load. If amps go up when a pump is restricted and filling the tank, the thrust bearing is bad.

    Yeah I know the local guys don't like CSV's, but that is how you know they don't have a clue what they are doing.
     
  12. leeelson

    leeelson Member

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    Well the amps don't go up, but they don't drop by 50% as the tank (8 gal) fills. At the start of the fill (no outside demand) it's running full bore (about 11.2 amps) then falls slowly to about 10.5 where it stays until shut off (tank full). It used to run at about 5-6 amps at shut off.
     
  13. valveman

    valveman Cary Austin Staff Member

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    It may not be a thrust bearing, but still sounds like a motor problem. Does it have a Grundfos motor?
     
  14. leeelson

    leeelson Member

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    Grundfos 25S20-11 2HP 25GPM 4' 11 Stage Stainless Steel Pump End
    96449947 Grundfos 1PH 2HP 230V 3 Wire Submersible MS402 Motor
    Grundfos 98315256 2HP 230V capacitor start/capacitor run control box
     
  15. valveman

    valveman Cary Austin Staff Member

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    Check with the people you bought that motor from. See if they are having problems with that model?
     
  16. leeelson

    leeelson Member

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    Distributor has had no bad reports. Suggests the problem could be with TDH but my understanding is that a larger TDH (late summer) would just decrease the flow, tending towards LOWER current draws. This pump is drawing almost 2.5 kW (11+ amps).
     
  17. valveman

    valveman Cary Austin Staff Member

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    Yeah, maybe they just haven't heard about it yet. Could still be a lack of flow past the motor requiring a flow inducer shroud. Won't know until you pull the pump. If the motor shaft stickup is less than 1.5", the thrust bearing is the problem and a shroud will probably solve it. If the motor shaft is still 1.49" or 1.5", then it is probably the top bearing in the motor, which is the one I think they are having problems with.
     
  18. leeelson

    leeelson Member

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    Sigh.

    First, let me say that this is a great forum and I really appreciate the time and effort people put into helping others.

    I've decided to bite the bullet and replace the pump and motor with a different brand (likely a Goulds GS series but input is welcome). I have some misgivings about this since I went through the process of abandoning a VFD and installing a CSV in early 2016 (see long thread https://terrylove.com/forums/index.php?threads/well-pump-help.63737/). I also had problems selecting a CSV that worked (see long thread https://terrylove.com/forums/index.php?threads/pressure-tank-sizing.64492/#post-477223). Ultimately things seemed to work out well using a CSV 125 60-1 so I want to make sure that the new pump and motor will also work well with the CSV. (Note that the dead head pressure on the Grundfos when installed was 100 PSI and that the CSV sits 20' below the surface. Also, though never adequately measured, I suspect draw down is minimal and water levels pretty constant) The max pressure of the current system is about 67 PSI, so a 40/62 setting works pretty well. It originally took about 30 seconds to fill with no load (much to the chagrin of installers mistakenly looking for a 2 minute "cycle" time ) but with the degraded motor, it now takes about 1 minute to fill. If these numbers are good, I'm wondering whether the bearings are likely to go out again or whether the bearing problem is likely elsewhere. (I'll certainly add a cooling shroud.) Is it possible that the low flow rate (1 GPM) forced by the CSV is the cause of the failure even though it is for a short period?

    This:
    http://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2014/11/GSSPEC-R1.pdf
    Is a link to pump curves for Goulds. (It's too large to upload)
    In looking at pump curves, I have some questions:
    1) Does it make sense to take my maximum likely TDH (300), lowest reasonable flow needed (15 GPM with outside irrigation) and pick a pump that way?
    2) How do I choose between the 13GS20 and 18GS15, both of which satisfy 1)? Is there a way to look at the Grundos pump curve and find a Goulds pump that is very similar without knowing the exact TDH but knowing the dead head Grundfos pressure?
    3) With the CSV, how important is the minimum operational flow given the short amount of time the pump is running at 1 GPM.
    4) Other than cost and power use, what is the downside to slight oversizing of the pump?
     
  19. Reach4

    Reach4 Well-Known Member

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    I think you are jumping the gun... I suspect you may still have years of service on that pump...

    Even so, if you do pull the pump, put on a flow inducer sleeve on there. Costs almost nothing

    Thinwall sewer pipe is the stuff of choice. solvent weld D2729 sewer pipe: OD 4.215 ID 4.056

    You could use thicker stuff if you have the room... Schedule 40 pvc would be 4.5 OD, and you would need more cuts to get the flex to clamp it in place.
     
  20. valveman

    valveman Cary Austin Staff Member

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    Pump Controls Technician
    Location:
    Lubbock, Texas
    It is very unlikely there is anything wrong with the 25S20-11 Grundfos pump. I think the motor is the problem. You could just get a regular 2HP Franklin motor to put on the Grundfos pump. I'll bet when you get that out Grundfos will replace the motor for you if it what I think it is.

    You should be able to run that pump at 1 GPM 24 hours a day without hurting anything. As I said I have the same pump at my house, and my 3 GPM drip system in the garden means the pump hasn't shut off in over two months because we are in a drought. It is also a 12 year old pump and it still goes from 12 amps to 5 when the CSV is restricting the flow.

    It is important that the 1 GPM goes past the motor, so a shroud would make sure than happens. But if the motor wasn't getting proper flow past it, it would still get hot and any flow rate.

    If you do change pumps stay with a 25 GPM as an 18 or 13 builds a lot of extra back pressure that isn't needed. TDH under 300' you want to stay with the 25S20-11 or use a Goulds 25GS20.
     
  21. leeelson

    leeelson Member

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    Nevada
    The idea of replacing the motor with a Franklin is attractive. Some concerns:
    1)Which model? There are many Franklin motors listed (http://www.franklinwater.com/products/motors-controls/4-inch-submersible-motors/#OrderInfo) with parameters I don't understand like "SF" "STK" "thrust"
    2) Is the Franklin motor compatible with the Grundfos pump? Attaching the 2 is straightforward? What about the Grundfos control box which seems to put out 330V. Is this compatible with the Franklin motor?
     
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