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Thread: DC Pressure switch recommendation

  1. #1
    Join Date
    Dec 2012
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    Eastern Washington
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    DC Pressure switch recommendation

    I have an existing solar pump setup used for livestock watering that doesn't work correctly - it overflows the trough regardless of what float valve setup I have tried. Since the trough is located at some distance from the well, and it is moved periodically I would like to implement the ON/OFF control using pressure feedback from the float valve, rather than running extra wiring (and trenching) for a level switch. I'd like some advice on adjustable switches that can accomplish this, as the pressures involved are pretty low.

    The system uses a SHURflo 9300 submersible pump and Best Pump Controller LCB 902-200. That provides for shutoff if the shallow dug well runs dry and on high pressure.

    It pumps very slowly, maybe 2gpm, from the well into a small bladder tank set at 15psi, and from there through a 1500 ft run up to a trough. What I was sold as part of this "package" system to do this was a private label Micro Pressure switch, SPDT, which activates on increasing pressure. But what happens is the float closes very slowly and it overflows the trough somehow, wasting the little bit of water that is available there.

    I think I need to alter it with two p-switches - a high pressure OFF and a low pressure ON. This is how it is done on every domestic well setup I've ever been around. But the trick is I need DC switches - and ones that I can reliably adjust for setpoints that are only like 5-20psi.

    Any advice on this would be greatly appreciated - thanks.

  2. #2
    Join Date
    Sep 2005
    Location
    Greenville SC
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    674
    electronic pressure switches will do what you want, but usually have low current outputs. You can, with those I've used, set an "on" range or use zero and infinity as one end. Many (most?) have 2 outputs. I've used products from Hydac and ifm extensively, and had good luck with both. Automation Direct offers them as well.

  3. #3
    Join Date
    May 2017
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    SCV Ca, USA
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    66
    Quote Originally Posted by Clodbuster View Post
    I have an existing solar pump setup used for livestock watering that doesn't work correctly - it overflows the trough regardless of what float valve setup I have tried. Since the trough is located at some distance from the well, and it is moved periodically I would like to implement the ON/OFF control using pressure feedback from the float valve, rather than running extra wiring (and trenching) for a level switch. I'd like some advice on adjustable switches that can accomplish this, as the pressures involved are pretty low.

    The system uses a SHURflo 9300 submersible pump and Best Pump Controller LCB 902-200. That provides for shutoff if the shallow dug well runs dry and on high pressure.

    It pumps very slowly, maybe 2gpm, from the well into a small bladder tank set at 15psi, and from there through a 1500 ft run up to a trough. What I was sold as part of this "package" system to do this was a private label Micro Pressure switch, SPDT, which activates on increasing pressure. But what happens is the float closes very slowly and it overflows the trough somehow, wasting the little bit of water that is available there.

    I think I need to alter it with two p-switches - a high pressure OFF and a low pressure ON. This is how it is done on every domestic well setup I've ever been around. But the trick is I need DC switches - and ones that I can reliably adjust for setpoints that are only like 5-20psi.

    Any advice on this would be greatly appreciated - thanks.
    The way I see it is; you need to address two problems to accomplish your goal. One is to prevent overflow thus avoid wasting water and the other is how to shut the pump off when bladder tank is full.

    In order to have a rapid shut off at the trough vs slow float valve closure you can install a battery operated irrigation valve available at home centers. You can use a float switch similar to condensate overflow switch to control the valve.

    Batteries on these gizmos last a year or a bit more depending on usage. You eliminate running wires to the pump. Home centers sell them.This setup becomes necessary because you have a bladder tank that serves as a surge tank to keep an ample water supply. In fact this tank contributes to the problem. Since you need it you just have to find a way to work around it.

    The pressure switch that came with your pump can still be used to control it. If that was recommended by the vendor then I assume it's ok to use.. . if not the right size you can shop around.

    You really don't want to shut the pump when the trough level is high, you just want to shut the water off but you need to keep the pump running until the bladder tank is full.

    The pressure switch will shut the pump off.

    $60 bucks will probably get this done.
    Last edited by myspark; 08-30-17 at 09:03 PM.

  4. #4
    Join Date
    Aug 2004
    Location
    Northern illinois
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    15,657
    are the critters beating on your float or something?
    Bob

  5. #5
    Join Date
    Jul 2009
    Location
    Mesa Arizona
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    254
    For controlling the level in the trough you might consider using one of the level controls commonly used in clothes washers. Simple and adjustable over about a foot in water height.

  6. #6
    Join Date
    Dec 2012
    Location
    Eastern Washington
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    31
    Quote Originally Posted by petersonra View Post
    are the critters beating on your float or something?
    Cattle definitely do that, but in this case I don't think it's the issue. I used a submerged valve with the float on a bobber. As long as the trough is more than half full they can play with it and it doesn't hurt anything.

  7. #7
    Join Date
    Dec 2012
    Location
    Eastern Washington
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    Quote Originally Posted by myspark View Post
    In order to have a rapid shut off at the trough vs slow float valve closure you can install a battery operated irrigation valve available at home centers. You can use a float switch similar to condensate overflow switch to control the valve.
    I like this idea. It seems like it would be a lot less finicky to set, and more reliable. The batteries are a complication, but I'm already changing fence batteries every couple weeks, so not a huge one.

    I haven't used one of these condensate overflow switches before - are they an electronic contact type switch that opens when the contacts are submerged? If so, I like this idea. Mechanical floats are trickier to keep working with ice and livestock. I could make a mount to protect a solid state switch.

    Do these switches have any provision for deadband or do you have to mount two of them? I don't want it to cycle if water level is just touching.

    Thanks.

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