Irrigation circuitry

Discussion in 'Irrigation' started by 1idejim, Jun 26, 2011.

  1. 1idejim

    1idejim LawnSite Fanatic
    Posts: 8,872

    this is taken from something that i am working on right now. it's a 1idejim thing :)


    Irrigation circuitry:

    There are three types of low voltage electrical circuitry involved in irrigation field wiring.

    Series circuits:
    An electrical circuit where there is only one path for the electrons to flow.
    Traditional automated irrigation systems are wired in series.
    Series systems use one shared common and individual valve wires.

    Parallel circuits:
    An electrical circuit where there is more than one path in which the electrons may flow. Two wire systems are wired in parallel which requires much less wire for the wire path itself.

    Combination circuits:
    Combination circuits use both series and parallel circuits. We normally see a combination circuit when there are two or more valves wired parallel in a valve box or wired parallel via a splice in the field and connected to a single wire at the controller.

    To determine what the resistance of the solenoids in a combination circuit is, the solenoid resistance is divided by the number of solenoids wired parallel.

    Example:
    Resistance - 30 ohms x 2 solenoids = 15 ohms.
    Resistance - 30 ohms x 3 solenoids = 10 ohms.

    These same solenoids wired in series would measure much higher.

    i hope this helps and doesn't confuse any issues that anyone is involved with right now.
     
  2. i guess the issue is determining if you are dealing with multiple solenoids in a combination circuit or if you are dealing with a solenoid developing a short.

    so from what I learned from you yesterday regarding using amps to help eliminate parts of a wire run.
    24V/15-Ohms is going to require a controller with a 1.5 to 2 amp fuse. So a blown fuse sending the assumed message that we have a bad solenoid may not be the case.(Potential troubleshoot method) Carry a 2 amp fuse and for a short test plug it in and see if multiple zones don't seem to fire on.

    Obviously if the multiple zones are wire at the terminal then its a non-issue.

    Jim?
     
  3. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,494

    Current is the thing, when you get advanced with solenoids. With two-wire out there, we should all have low-range clamparound ammeters.
     
  4. Does the Dynatel 573A have a low range clamparound?
     
  5. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,494

    It fits an inductive clamp, but it doesn't measure currents. I wouldn't think that to be a useful function in any locator.
     
  6. 1idejim

    1idejim LawnSite Fanatic
    Posts: 8,872


    separate issue peter, our conversation pertains to location not operation. you should never increase the fuse to accommodate the system, the system should accommodate the fuse
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,494

    I have no problem up-sizing a fuse in an electromechanical controller, but that is way off the beaten path nowadays.
     
  8. 1idejim

    1idejim LawnSite Fanatic
    Posts: 8,872

    actually, the higher end locators do use current measurements for direction purposes.
     
  9. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 46,494

    Are saying they provide an actual number for current?
     
  10. I know about the danger of upsizing a fuse. My suggestion was for a shortterm test to determine if multiple valves have been strung on a single zone wire. After that then put the proper fuse back in.
    Posted via Mobile Device
     

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