controlling pump

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by mak123, Jul 30, 2009.

  1. mak123

    mak123 New Member

    Messages:
    36
    Like below drawing, pump connects to tank and I need to control pump like this: (1) pump starts when pressure in pipe drop under 30psi, pump stops when pressure reachs 70 psi, and (2) pump stops when water in tank almost empty ( sensored by the float switch), pump starts when water full and pressure switch indicates less than 30 psi at the same time.(even water full, but pressure is over 30psi, no need to start pump)

    So, I need to set up two power on-off switches, one is pressure switch the other is float swich.

    Can anyone let me know who can I actually hook-up and set-up these two switches so that pump operates(stop and run) properly?

    Thanks much

    Attached Files:

    Last edited: Jul 30, 2009
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,893
    Location:
    New England
    Not sure what the second tank is. To prevent the pump from running with any small water usage, it is common to run the outlet of the pump to a pressure tank (a bladder tank). There's a check valve so once filled, the pressure is retained. The pump control switch is place by this tank and typically has a 20# difference...turns on at say 30# and off at 50#. To prevent it from running the supply tank dry, a simple float switch could be used to interrupt the current to the pressure switch.
  3. mak123

    mak123 New Member

    Messages:
    36
    The reason for second tank is one tank is not enough volume of water so I wanted to connect two tanks...

    How many pressure tank I need? one or two? where to put it...after pump or before pump?

    Thanks
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,893
    Location:
    New England
    As noted, the pressure tank goes after the pump. Essentially, the setup I'm suggesting is very similar to that which would be used (in the USA anyways) if you had a well and wanted pressurized water in your house.

    So, it's in order...supply (in your case tanks) to a pump into a check valve to a pressure tank and then your house.

    The switch to control the pump needs to be near the pressure tank. The pressure switch is a common thing here and available in preset values of 20/40, 30/50, 40/60, and 50/70 ratings (although they are adjustable).

    You'd want to power that switch with a float switch in case the tanks ran dry; preventing the pump from running.

    The pressure tanks come in various sizes. Post in the pumps and wells section of this forum and you'll get some more help.

    If you need a pump to fill the tanks, a float switch to turn it off would be necessary. I suppose you could do that with one pump and some valves to enable it to push the water to the tanks, but control would be a little messier.
  5. Thatguy

    Thatguy Homeowner

    Messages:
    1,460
    Location:
    MD
    I think you said:

    A
    pump starts when pressure in pipe drop under 30psi, pump stops when pressure reachs 70 psi,

    B
    pump stops when water in tank almost empty ( sensored by the float switch),

    C
    pump starts when water full and pressure switch indicates less than 30 psi at the same time.
    water full, but pressure is over 30psi, no need to start pump


    Just like back at school the first step is to confirm that this Truth Table is correct

    A
    pressure <30, water not empty, pump on
    pressure >31?, water not empty, pump on
    pressure >70, water not empty, pump off

    B
    pressure <30, water empty, pump off
    pressure >31?, water empty, pump off
    pressure <70, water empty, pump off

    C
    pressure <30, water full, pump on
    pressure >31?, water full, pump off

    Seems like you need a water empty and water full switch. Neither being on means "water not empty."
    Seems like you need a less than 30 psi switch, a more than 30 psi switch and a less than 70 psi switch.
    Last edited: Jul 30, 2009
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,488
    Location:
    Cave Creek, Arizona
    switch

    You have made it more complicated than necessary. A float switch to cut power to the pump when the level in the tank is low, and a pressure switch set a 30/on, 70/off, in series with the float switch will do everything you want it to.
  7. Thatguy

    Thatguy Homeowner

    Messages:
    1,460
    Location:
    MD
    That gives A & B. How to do case C?
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