2-Wire Systems: wire tracing and servicing

Discussion in 'Irrigation' started by PurpHaze, Oct 6, 2007.

  1. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    LondonRain brought up some interesting insights that I'd like to explore further before committing my new design to a 2-wire system.

    I'm assuming that this is because the wire path between the decoders in the field and the valves themselves is not "open" unless the decoder is communicating with them? Can you trace between the controller and the decoders like in a multi-wire system?

    Do the decoders act kinda like an "isolation valve" in that signals only go between the decoder and the valves when the controller activates the decoder?

    That's a given on anything I install, anything major we repair or problematic systems where I will document main line and valve locations for future reference. Just yesterday I was able to reference a scaled "valve location as-built" I'd made up on a newer system (30+ field valves) where we didn't have an original contractor as-built. We had spent many hours locating the valves and putting them down on a plan since I just knew the site guy would not keep the boxes uncovered and I just knew that we'd have future problems since the original system was installed by one of our least favorite contractors. I was able to direct Leo via Nextel walkie-talkie to the general area where the suspect hung valve was located and he was able to locate it and reair the problems. He said I was within about 3' of where I'd indicated.

    What type of system decoders/controller does this one have? Are they installed in their own boxes or as part of the valve/box installation? Are they single, multiple valve decoders or a combination?

    By its very nature the decoders give you another level of "controller" interface and potential problems which could become a real PITA.

    Was this system installed by another contractor or did you do the install yourself?
  2. hoskm01

    hoskm01 LawnSite Fanatic
    Messages: 5,690

    New field Purp?

    Do I understand correctly that the only real advantage in 2 wire is programability and reduction in copper?
  3. londonrain

    londonrain LawnSite Silver Member
    Messages: 2,129

    Since you only have 2 wires and it must be a continuous wire with no tee-offs in the wire you trace the entire wire path all over the area for every valve not just one valve . Most of the time doubling back the same path since it is continuous wire run or it could be a dead wire at a valve and you are tracing back the same wire again. The field receiver/decoder must be activated for the current to pass through and activate the solenoid, if dead receiver then no solenoid signal, no solenoid activation/coiling and the 521 passes right past. Yes the decoder acts like a isolation valve, no signal no activation of the solenoid. This is a Hit 2 wire system and they are installed in their own boxes with decoder...and another contractor installed the system.
    Yes it is a pain trouble shooting. What I end up doing is using my station master and a solenoid then testing the 2 wires between two valve locations, if good move on to the next area. The last time I was out trouble shooing we had a dead wire and since I do not know the exact path of the wires it was a real pain... one of the decoders went bad so it showed a short on the station master when hooded up on the 2 wires, so I had to disconnect decoders until if figured out what was happening...once again just a real pain...
  4. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    Just curious about new technologies available to us. :)

    What I'm keenly interested in is the ability to add on to an existing system with just the two wires present. We're constantly in a state of flux as things (such as buildings, play boxes, asphalt play areas, etc.) are brought in and then removed or modified.
  5. PurpHaze

    PurpHaze LawnSite Fanatic
    Messages: 5,496

    It's my understanding that you can tee into the 2-wire path to add on. Does it have to be a "broken tee" (where you'd tee in, go to your new set of valves and then return to the tee-in point to continue the wire path to your existing decoders/valves further down the line) or an "unbroken tee" where you just tie in for your new spur and the old spur stays intact?

    Guess I'll have to do some more reading to better understand the wiring routing. :)
  6. londonrain

    londonrain LawnSite Silver Member
    Messages: 2,129

    Yes you can tee in. Cut old wires, connect new wires to one end of cut wires and run new wires, double back new wires and connect to the other end of the old cut wires.
  7. londonrain

    londonrain LawnSite Silver Member
    Messages: 2,129

    You only want one dead end wire path.......
  8. londonrain

    londonrain LawnSite Silver Member
    Messages: 2,129

    Wiring is one of the most important parts of a 2 wire system..Here is a pic of the connectors Hit supplies with each decoder.

  9. BrandonV

    BrandonV LawnSite Platinum Member
    Messages: 4,628

    now with the hunter acc you can run up to 6 paths and they you can dead end all you want, at least from what I understand. nothing had to be looped, and you could tee in anywhere you want. i also used the pre braided wire.
  10. londonrain

    londonrain LawnSite Silver Member
    Messages: 2,129

    Correct if your controller can run 6 paths you will have 6 dead ends, 1 for each path. The Hit logic 1 has one path only thus 1 dead end path. You will not want 1 path with more than one dead end. With the Hunter 2 wire you connect the decoder on the 2 wire path, then you can run up to 150f of extra wire from decoder to the solenoid. You will not want to tee into the 2 wire and run more of the 2 wire to the solenoid and dead end it.

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