Reversed pressure switch

Discussion in 'Pumps and Tanks Well Forum & Blog' started by alternety, Dec 8, 2006.

  1. alternety

    alternety Like an engineer

    Messages:
    671
    Location:
    Washington
    Does anyone know of a pressure switch I can use with my well system that OPENS the contacts to run the pump and closes them to stop?
  2. Seekonk Supply

    Seekonk Supply New Member

    Messages:
    2
    I'm confused. How is electricity going to flow, with an open circuit?
  3. Rancher

    Rancher Guest

    Sure, just use the contacts to operate a relay, or pump contactor, what you want is a double pole double throw relay, which means you have contacts for either normally open or normally closed, any contractor electrical supply house will have what you need.

    Rancher
  4. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    May I ask why?

    bob...
  5. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    Go to www.grainger.com and look at stock numbers 6B452, 5B416, 2FG93, 1V630, And 6B437. Perhaps one of them will suit.
  6. speedbump

    speedbump Previous member

    Messages:
    4,540
    Location:
    Riverview, Fl.
    Boy! are they proud of their products!
  7. alternety

    alternety Like an engineer

    Messages:
    671
    Location:
    Washington
    One of the Square D units looks good.

    The reason - the motor control uses an open circuit to run. I am not sure why they did that; but they did. The power does not flow through the pressure switch contacts; just a control current.

    Rancher - I know. I just want something that looks "regular" to handle it. I have other things to joust with.
  8. Rancher

    Rancher Guest

    Can you tell us what the motor control looks like, it seem like you probably have what you already need to do the job.

    Rancher
  9. alternety

    alternety Like an engineer

    Messages:
    671
    Location:
    Washington
    It is a Baldor BC140. It supplies variable speed DC motor control. It supplies up to 180 VDC at about 11 A.

    I am going to check with the factory and see if there is another point inside that would accept the close to run signal. There is a set of pins that allow that but they don't actually remove power from the motor when it is stopped. I found this out experimentally. The motor hums when it is "off".
  10. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    What happens if you use a switch in the normal way to simply disconnect power from the thing that is giving AC to the controller? I guarantee it won't run if there is no AC.
  11. alternety

    alternety Like an engineer

    Messages:
    671
    Location:
    Washington
    Switching the DC would circumvent the soft start and I don't believe they recommend switching the output. Switching the input would work but I just have the feeling that it would be better for the controller if it did not keep turning it on and off. I am not sure how soft start will react to this approach either.

    I also have to implement low water protection. The source of this signal is a low voltage relay contact. It is a double throw so there is not a problem.

    I would really just rather use the provided control points in the controller.
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