If 240 Ohms of Resistance is normal...

Discussion in 'Irrigation' started by deekay1622, May 29, 2014.

  1. deekay1622

    deekay1622 LawnSite Member
    Posts: 47

    Hi All,

    Today I found a valve that was drawing 0.08 Amps and not actuating. I assumed it was defective, but then I did a little research.

    I turned on another valve and it also drew 0.08 Amps of current and the valve did actuate.

    After a little research, I think I have a Griswold 2010 Normally Closed Low Power Solenoid Valve. It draws only 0.10 A in normal operation.



    So, using Ohms law I'm assuming 240 Ohms would be normal resistance.

    Any ideas on what would be outside "normal" range and indictae a defective solenoid?

    Thanks.

    photo (2).jpg
     
  2. 1idejim

    1idejim LawnSite Fanatic
    Posts: 9,313

    Why do you assume 240 ohms is the correct resistance?
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  3. 1idejim

    1idejim LawnSite Fanatic
    Posts: 9,313

  4. deekay1622

    deekay1622 LawnSite Member
    Posts: 47

    Hi Jim,

    This is the valve I think I have:

    http://www.griswoldcontrols.com/pdfs/F-5373.pdf

    I used this Ohms Law Calculator:

    http://www.bowdenshobbycircuits.info/ohmslaw.htm

    It showed me that if normal current is 0.10 Amps and I'm operating on 24 Volts AC (hooked up to a Calsense ET2000e) then my Ohms resistance should be 240.

    I'm wondering if there is a standard deviation away from normal that indicates a defective solenoid?

    Thanks for the help. I'm hoping to be thorough before chucking this solenoid and ordering a new one.
     
  5. 1idejim

    1idejim LawnSite Fanatic
    Posts: 9,313

    We went through a long debate less than a year ago about ohms law. Some of it not pretty :hammerhead:

    I have a ballpark measurement I use, I read the specs of a new solenoid and adapt the measurements to fit the ocassion.

    Say rainbird specs say 30-39 ohms / .41 inrush and .28 holding amps @ 24 vac I can determine the brand and get an idea of the condition of the solenoid from the controller. Bad wire paths can throw a wrench into troubleshooting as can a deterioration of any other electrical component.

    You say you have working valves, measure them for comparison, call griswold tech support for the resistance values and measure and benchmark the entire system. It matters more what you are looking at in the field than what a new component should read when it leaves the factory.

    Good luck :)

    Griswold (949) 559-6000
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    Last edited: May 30, 2014
  6. deekay1622

    deekay1622 LawnSite Member
    Posts: 47

    Thanks, Jim.

    Good advice. I'll call Griswold for reference and proceed accordingly. I'm in agreement that I should benchmark based on the other valves, especially since the whole system was installed at the same time and the valves are approximately the same distance away from each other(+/- 100lf ).
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,324

    Griswold does make some ultra-low-draw solenoids, and they are massive. I saw them in the mechanical-controller days, so we weren't caring about their resistances, since they seemed to work, period.
     
  8. 1idejim

    1idejim LawnSite Fanatic
    Posts: 9,313

    I spoke to Rocky at griswold, what a great guy.

    Seems they no longer make that valve or solenoid. The replacement # is 4333-02
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  9. irritation

    irritation LawnSite Gold Member
    Posts: 3,221

    I wonder who buys them?
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,324

    That valve found its way into some insanely over-spec'd residential systems I encountered. Griswold Series 2000 valves (with or without massive low-current-draw solenoid), and Thompson fixed-arc gear drive rotors, built along the same lines as the Griswold valves, with a cast-iron body enclosing brass works.
     

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