Need help finding the common wire

Discussion in 'Irrigation' started by captken, Jan 29, 2013.

  1. captken

    captken LawnSite Bronze Member
    Messages: 1,704

    System is over 25 years old. Hasn't run in over 10 years. Park, 8-10 acres.
    Repairing busted water lines everywhere. Found 2 valves with the 521a.
    Using the 521a to locate all my wires. 8 strand multi colored.
    Working on identifying nicks and breaks. Found a 20' gap under a mature Pine Tree.
    Unable to continue trace past this point.

    Repairs made to busted pipe located beyond this spot, spliced into this multistrand at this point to pick up the trace.
    8 strands 4 colors...2 black....2 green....2 yellow....2

    Not to be intimidated, I continued with my trace until I ran out of range of the transmitter.

    My question, how can I determine which one is the common wire?
    I need to find the valves.
    [short of running my aerator down the wire line which I am temped to do at this point]

    Thank you in advance for your help, kenny.
  2. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    The common will share continuity with multiple valve and measure resistance values comparable to the valves you have found.

    The color scheme leads me to think that you have 12/14ga. single strand rather than 18 ga. multi. Is there a sheath?

    A short to earth measurement will onl tell if you have earth contact or not but if the wire measures open to earth, i would try pairing to the other wires or trace it first.

    An indication of the common should have been visual at the other valves that you found.
    Posted via Mobile Device

    Another thing to think of is, the green wires could be common and spare. Other wires could be valves and spare.
  3. captken

    captken LawnSite Bronze Member
    Messages: 1,704

    Sorry, not clear on my part.
    Multi colored 8 straind conductor wire present at the junction box had been respliced with a 4 color 8 straind conductor wire.
    The wire size is 12g.
    I did a trace from the clock to a point and lost signal.
    Repaired a busted pipe, cut the wire to trace back in the direction towards the clock to where the signal was lost.

    About a 10' gap exist where I think the wire is damaged.

    I noticed that the wire where I cut was not matchable color wise to what I started out with.

    On the two valves I found, the common wire was black.

    I need to figure out what the guys before me have done..
    A puzzle indeed.

    thanks, kenny.
  4. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    Your maximum one way distance to the valve is around 3200ft using 12/12 and 4000ft using 12/10 according to my figures, a bit further if you use the book.

    That allows for a slighter Vdrop.

    I mention this because of the size of the site, a man can get lost and be way too far out.

    You can avoid searching areas bogus areas by creating search limits on larger properties.

    When you took this site on i would think that you were given a walk about, gathered as much information as possible.

    Do you know where the limits of each zone are? Or should be?

    I ask because you are looking for 8 valves and 2+2+2+2=8. That would make sense for 7 valves and 1 common.

    Being built in the 80s and prolly designed by a LA, i can see a black common with spare, grn w/spare, yel w/spare and red w/spare. that would make sense for 3 valves.

    That would mean that there would be another junction box that would prolly run in another direction.

    On the other hand there could be 1 blk com w/spare and 2 grn, 2 yel and 2 red but that only accounts for 6 valves? That would mean there is another junction box?

    Another scenario would be 1 blk common w/spare, each of the grn, yel and red (6) supporting 1 valve each w/2 wires supporting 2 valves (6+2=8). That would eliminate the extra junction box.

    This site is perfect for a pro 800 using broadcast. There is a technique for locating using a moving sweep, the 501 can do it also.

    When you lost signal, did it fade? Peak then fade? Drop suddenly? What was your distance? How were you grounded? Have you grounded the far end? (Sounds strange but helps short bridging) What is your output voltage? (High goes deep-low goes long) Short to earth? Condition of found valve wiring?
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  5. ArTurf

    ArTurf LawnSite Platinum Member
    Male, from Ark
    Messages: 4,471

    [On the two valves I found, the common wire was black.

    I need to figure out what the guys before me have done..
    A puzzle indeed.

    thanks, kenny.[/QUOTE]

    Just guessing the common on the other valves would be black. But you never know for sure on these things. Go with it and see what happens, nothing to lose.
  6. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    I spoke with Captken yesterday, nice guy.

    One of the methods/techniques that we discussed was identifying a single wire with a multimeter in a couple of measurements.

    With access to both ends of a wire path, one may pair the wires with one measurement and identify them with the next measurement.

    In Kens situation he has 8 wires.

    At one end the wires are stripped and a wire nut is used to connect 2 wires. This leaves him with 4 pairs. Each pair is also taped to prevent separation when wire nuts are removed.

    At the other end pair continuity is measured and wires labled.
    1&2 3&4 5&6 7&8

    Once paired and labled #1 wire is inserted into the earth, #2 is isolated from the earth.

    At the other end the wire nuts are removed, the multimeter adjusted to megaohms and the black probe inserted into the earth.

    A resistance measurement will be present only on the #1 wire, #2 will be its paired wire.

    This method is very fast when one has a helper and works well when there is no tone/probe handy.
    Posted via Mobile Device
  7. captken

    captken LawnSite Bronze Member
    Messages: 1,704

    Well, I went back today, yesterday was storming. I need to back up and do what Jim suggested to do to fix the signal gap in my wire trace.
    What I did instead was watch over my crew doing the pipe repairs and tinkering a little with the 521a. I don't know about you, but for me, I have to concentrate and not be distracted while learning how to use the wire tracer....and having a couple guys to supervise....not that I don't trust them mind you, I just want to be sure the job gets done right the first time.

    This is beyond where Jim and I talked about the wire siganl gap.

    What I was able to do is take the bundle of wires, in full sunlight, look at them closely.

    [[8 strands 4 colors...2 black....2 green....2 yellow....2 ]]quote. was in the first post, and I was confused however...

    In full sunlight, scraping the insulation deeply with my knife revealed not the above but, 1 black 1 grey 1 blue 1 green 1 yellow 1 white 1 red 1 orange.
    I guess being in the ground for 25+ years took a toll on the paint pigment in the insulation.

    Using white as the common, tried to get consistant ohm readings but they were all over the place.

    I tried a combo of White and Blue, on the 521a and took me to a valve using White and Yellow.??
    Whats up with that?

    I went back and tried the combo of White and Yellow, it took me directly over a valve buried 2-1/2 that had White and Orange.

    So I know that the common, is white at this leg which suggest that no one has done repairs since it was installed.

    A puzzel indeed, but a very interesting puzzel.

    This 521a is great tracing a wire over a long distance. I need to hone my skills locating valve and learn to trust the machine. I need get caught up on work that need to be done up to this point.
    Last edited: Jan 31, 2013
  8. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    A job like this will teach you a lesson about yourself. What your weakness' are as well as your strengths.

    You should practice as much as possible with your DMM before spring startups. I would say multimeter knowhow is the area most techs lack the most.
    Posted via Mobile Device
  9. captken

    captken LawnSite Bronze Member
    Messages: 1,704

    Jim sorry, been ill since Friday last week, thanks for your insight into the problem here.
    Plan to go back to work tomorrow. However, using a dmm found 3 wires with continuity, and used the 521a to find 3 more valves.
    They look pretty good considering being buried in the dirt 2-1/2' a quarter century ago!
    MLGW gave me their chart so I can map the system out for future reference. 5 valves found so far, 64 sprinkler heads so far. Finding lateral breaks and some other minor problems.
  10. 1idejim

    1idejim LawnSite Fanatic
    Messages: 11,358

    You are doing well, gimme a call if you get stuck.
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