Looking for a low pressure switch or ideas

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emerika
emerika Registered Users Posts: 12 ✭
in Solar Water Pumping #1
I have a 20' water tower with a 900 gallon water tank on top that is filled from a well pump that has its own solar panels and only runs when there is sun (obvioulsy). However, you can power it from AC.

I am installing a pressure pump to provide water pressure to the house. I would like to set this system up such that if the input pressure at the pump drops to 2-3 PSI, the well is powered via AC until it gets back up to 5-6 PSI. I just want to insure there's always water in the water tank.

So far I have been unable to find any differential water pressure switches that work in this pressure range. Anyone have ideas.

thanks in advance-
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
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    Re: Looking for a low pressure switch or ideas

    Is there a reason you cannot/don't want to use a float switch?

    Generally, pressure switches are not that accurate or reliable over time (not that float switches don't have their issues as well).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
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    Re: Looking for a low pressure switch or ideas

    A FLOATING switch (one that has a mercury switch in it, tied off to the side of the tank) as opposed to a float switch is probably the ticket.A floating switch comes on (or off) as it floats past horizontal. It can be placed any where in a tank (or casing) such that when the water drops, it falls past horizontal and turns on (or off). When it float up past horizontal it turns off (or on) A float switch is subject to all kinds of issues, while a floating switch is nearly fool proof.

    Tony
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  • audredger
    audredger Solar Expert Posts: 272 ✭✭
    #4
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    Re: Looking for a low pressure switch or ideas

    I vote float switch ... works good, lasts a long time, painted black for easy identification!
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #5
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    Re: Looking for a low pressure switch or ideas

    Another type consists of a tube with reed switches at set levels inside and a doughnut shaped float with a magnet in it that slides up and the tube as the water level changes.

    Tony's floating switch is probably the most fool proof. Last float type (float on an arm) the float came off and water ran down the street all night - at 4 USD per m3.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #6
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    Re: Looking for a low pressure switch or ideas

    If a float switch failure is going to be a problem--pipe an overflow drain and add a second switch/sensor to an alarm/backup power cutoff...

    Guarantee that something will go wrong and cause lots of damage (like my sump float that stuck in the sump and just wiped out my central heater last week; alarm company that appeared not to program the water sensor, I ignored the excessive humidity with no visible source, no sump/water problems in the last five years, :grr:cry:). Now have a sump pump with dual floats, sensor box that alarms if 10 minutes of float on, AC power fail alarm, a separate local water alarm. raise new heater even higher in pit... :roll:

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #7
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    Re: Looking for a low pressure switch or ideas

    I like the probe type liquid level ( conductivity) sensors for reliable operation. No moving parts just 2 probes in the water. I have been using them for years in industrial applications in extremely harsh conditions such as open cooling towers with few problems. Check out Mcmaster-carr for different types of liquid level controls.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,746 ✭✭✭✭✭✭
    #8
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    Re: Looking for a low pressure switch or ideas
    emerika wrote: »
    I have a 20' water tower with a 900 gallon water tank on top that is filled from a well pump that has its own solar panels and only runs when there is sun (obvioulsy). However, you can power it from AC.

    I am installing a pressure pump to provide water pressure to the house. I would like to set this system up such that if the input pressure at the pump drops to 2-3 PSI, the well is powered via AC until it gets back up to 5-6 PSI. I just want to insure there's always water in the water tank.

    So far I have been unable to find any differential water pressure switches that work in this pressure range. Anyone have ideas.

    thanks in advance-

    We build them at my other job for the International Space Station. About 25K including shipping!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #9
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    Re: Looking for a low pressure switch or ideas
    Dave Sparks wrote: »
    We build them at my other job for the International Space Station. About 25K including shipping!
    That is a deal for low earth orbit! ;)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,746 ✭✭✭✭✭✭
    #10
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    Re: Looking for a low pressure switch or ideas

    It is a deal when you consider, five orders of magnitude pressure range on either side of the decimal point, differential at absolute pressure or gage, extremely high proof pressure, and the user can select a range within reason. The development costs are where we get a little carried away...

    Someone has to make something that the OP can afford?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Chuck46
    Chuck46 Solar Expert Posts: 95 ✭
    #11
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    Re: Looking for a low pressure switch or ideas

    Maybe this would do the trick[
    URL="http://www.clarksol.com/html/cj_Inst.cfm"]http://www.clarksol.com/html/cj_Inst.cfm[/URL]
    good luck Chuck
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