Why 24vac won't actuate a solenoid

Discussion in 'Irrigation' started by 1idejim, Jan 26, 2013.

  1. KrayzKajun

    KrayzKajun LawnSite Fanatic
    Messages: 10,737

    Ughhhhh someone wipe the drool from my mouth.... Brain is overloaded from all the numbers
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  2. irrig8r

    irrig8r LawnSite Platinum Member
    Messages: 4,553

    I've never measured resistance "from the controller" itself... or do you mean he measured the resistance of the solenoid via the wire path to/ from the controller?

    A reading of 180 Ω would make me suspect a partial connection or badly corroded wire connector (as you mentioned, checking the splices).

    You know what they say about "when you hear hoofbeats, think of horses not zebras"?

    Anyway, though it makes sense to suspect the insulation, please explain how you test the "short to earth" because it's outside of my limited knowledge and experience.
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,758

    It is never a given that any part of the controller output is grounded. That can make resistance-to-ground measurements superfluous, unless all conductors are tested.

    As noted, "I got 24 volts" says nothing about the actual circuit path quality.

    Even resistance measurements may turn up nothing. Old-time mechanical controllers gave zero info about electrical faults. This is where the clamparound ammeter came in, as it could show a higher-than-usual current draw on a solenoid that refused to go to shorted status while the repairman was watching. They had to have voltage applied to show the fault.

    The yellow clamparound ammeter was a Sperry model that had an extra range of 1.5 amps full-scale, good enough for the higher current draws of old-time solenoids.
  4. Sprinkus

    Sprinkus LawnSite Silver Member
    Messages: 2,326

    It wasn't me but I have been asked to troubleshoot a 100+ zone two-wire system installed in phases by several of the crappiest installers around. :rolleyes:
    One part of me says::weightlifter:
    The other part says::cry:
    And of course the non-part of me says::drinkup:
  5. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    If i had meant to include the controller i would have said "through the controller", i could have said "at the controller" which is a location, but didn't mean that. Instead i said "from the controller" which implies direction.
    In hindsight i could have chosen better words but i understood my Texas friend very well.
    As you should, that's what the books say and the teachers teach.

    You know what they say about "when you hear hoofbeats, think of horses not zebras"?

    Adjust a DMM to 2,000kohms and insert the black probe into the earth, touch the red probe to the conductor under test. >600,000ohms look at the splice. <600,000 look at the buried wire path first.
    I have no idea why that would be, you spend as much or more time with LV lighting and should be more familiar with a DMM than most of the irrigation forum members.

    2wire should be a cinch for you. Voltage drop, wattage and amp calc formulas should also be second nature by now.

    All that i am trying to accomplish is to bring to light a few simple tools that have been in use for decades that may help make troubleshooting easier.
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  6. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    They picked the best of the best IMHO, you are my hero Sprink.

    You get all the good jobs ::cry:
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  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Messages: 50,758

    repeat after me - "Time and Material"

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