VFD pump with standard pressure switch?

Discussion in 'Pumps and Tanks Well Forum & Blog' started by 25-06shooter, May 12, 2014.

  1. 25-06shooter

    25-06shooter New Member

    Messages:
    4
    Location:
    NC
    Eight years ago I installed a 1.5hp Grundfos VFD well pump when we built our house. Should have read the reviews first. The control box went out this evening. Instead of installing a new control box and wondering if I am going to have water every time I turn on a faucet I would like to install a standard pressure switch. Will this shorten the life of the pump? Is there a better option without installing a new pump?

    400' well
    Pump at 330' + 20' of head
    Water level is at 42'

    Calculated water usage is 13gpm
    Looking at a 52 gal pressure tank, or should I install a pressure reducing valve and use a smaller tank?
    Looking to use a 40 to 60psi switch

    This is my first post here, but I have been reading a lot the past couple hours and this site has by far the most info in one place that I have found.....just not exactly what I am looking for. :)

    Thanks
  2. Reach4

    Reach4 Well-Known Member

    Messages:
    2,432
    Location:
    IL
  3. 25-06shooter

    25-06shooter New Member

    Messages:
    4
    Location:
    NC
    Yep, missed that one completely. That is actually how I have it hooked up temporarily (without the pressure reducing valve) to get us through the night, but the pump is cycling very rapidly. I will go pick up a valve tomorrow morning and get it switched out.

    Thanks for the help
  4. valveman

    valveman Moderator Staff Member

    Messages:
    4,495
    Location:
    Lubbock, Texas
    A pressure reducing valve placed after the pressure tank will not solve the cycling problem. A pressure reducing valve placed before the pressure tank will deadhead and destroy the pump. There is a lot of difference between a Pressure Reducing Valve and a Cycle Stop Valve.

    I hope you can find a place to pick up a CSV, but most likely you will have to wait for one to be shipped to you.
  5. 25-06shooter

    25-06shooter New Member

    Messages:
    4
    Location:
    NC
    So it looks like I would need the CSV150 and install it before the tank and pressure switch. Is a 2 gallon tank enough? Will it hurt anything to use it without a CSV until one gets here?

    Also, I have 3/4" black plastic pipe run from the well to the house. It is rated at 100psi. I don't know how much pressure my pump is rated for, but I'm sure it would be over 100psi. Will the CSV let enough pressure by fast enough to keep from busting pipe?
    Last edited: May 13, 2014
  6. valveman

    valveman Moderator Staff Member

    Messages:
    4,495
    Location:
    Lubbock, Texas
    With a static water level of 42’, a 10 GPM, 1.5HP SQ can build 224 PSI on the pipe prior to the CSV. A 15 GPM series can build 185 PSI. 150 PSI is the maximum the CSV1 can handle.

    You could install a CSV1W in the well before it gets to the 100 PSI pipe. But you will need to have the pump pulled up a few feet to be able to put the CSV under the pitless adapter.

    I don’t know why anyone would install 100# poly anywhere, especially underground. The only reason anyone would install one of those VFD type pumps is just to make the extra money, so I don’t know why they wouldn’t put in stronger pipe as well.

    That 100# pipe will probably handle the backpressure as most pipes have a burst pressure 2 to 5 times the rated pressure, but I had rather stay close to the rated pressure.

    Your easiest option maybe to just install a large pressure tank and let the pump cycle as it will.

    If you had 200 PSI pipe underground, a CSV1A installed at the house and before the little pressure tank would be ideal. Any of those sizes of CSV’s will work with a 2 gallon tank, but we prefer replacing with a 4.5 gallon tank if you ever change it out.

    Without a CSV I would install an 80 gallon size pressure tank to limit the cycling somewhat.
  7. 25-06shooter

    25-06shooter New Member

    Messages:
    4
    Location:
    NC
    I went ahead and converted everything over to a pressure tank yesterday. Everything seems to be working great so far.

    A cheap plumber and me not paying enough attention when we built the house got me the 100# pipe. There won't be a next house, but if there was there are several changes I would make. :)

    Thank you for all the help.
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