Powering a water pump

System
System Posts: 2,511 admin
in Solar Water Pumping #1
I'm looking to use a PV panel to power a 12vdc, 80ma relay, which in turn, will run a 115vac water circulating pump.

The pump is part of a solar water heating system, so I will only need the pump to run when the sun is out or when the solar collectors get hot enough to heat the water.

With that said, here's my question:

Can I directly connect a properly-rated PV panel to a 12vdc relay, or will I need a voltage regulator as well?

Thanks in advance.
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Comments

  • System2
    System2 Posts: 6,290 admin
    #2
    Re: Powering a water pump

    What voltage is the output of the solar panel? That can vary quite a bit at times. To be safe and not burn up the coil of the relay, I would use a 7812 regulator. It has only 3 terminals. One is "ground", (that is negative). Another is for the INPUT (+ from the solar panel) and the third is 12 volt regulated output. Very easy to use and the back of the Radio Shack package will show you which pin is what. Don't mix them up. If I remember right, the 7812 can handle up tp 35 volts input.
    Probably less than $5.00 and is available at Radio Shack.
    I wouldn't do it any other way.
    Good luck
    Wayne
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Powering a water pump

    that regulator as most lm regulators do need a heat sink too or it could burn out. this is usually a finned piece of aluminum, but it can be a piece of solid metal with enough area to it to pass the heat well to the air.
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Powering a water pump

    Thanks Niel, I forgot to mention that.
    At it's max input of 35 volts, and a 12 volt load of .08 amps, the reg will pump out about 2 watts of heat and like Niel said, if you don't get rid of the heat, the regulator will cook itself to death.
    Wayne
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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Powering a water pump

    Thanks for the suggestions.
    Next stop, Radio Shack...
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