Trying to understand my 521 process?

Discussion in 'Irrigation' started by jcom, Jul 24, 2007.

  1. jcom

    jcom LawnSite Senior Member
    Messages: 791

    I am on a new customers property. Five valves and a master on the side of the building. One valve in a valve box. Eleven hooked up altogether. Two eight conductor cables spliced in the valve box. I separated one going to the as yet undiscovered five valves. I get a null out of the box all the way to the building where the cable goes out to the valve box when hooked to that open wire.

    When I hook it going the other way I get a null for about twenty feet and then nothing. I know the zones all work and we are trying to locate these valves for future reference.

    We are trying to narrow it down. Norwegian blood resulting in irrigation retardation as my wife says.
    Or not operating tools correctly.


    Hooked up my Krik-it at the controller (inside) and it also was unable to help me.
  2. Mike Leary

    Mike Leary LawnSite Fanatic
    Messages: 23,220

    The 521 is a great tool, but it can lead one astray, one of my guys followed
    a null into a building next door! Are you using the grounding probe & not the
    common? I've had luck, if it's a pro system, of firing the zones & thinking,
    "where would I spot the valves?" & probing with the 521 in that area. Worst
    case is they used 6" pit boxes & the turf & mulch have covered them. Use a
    long philips head to probe as you follow the perceived path. Most problems I've had w/the 521 is improper ground, make sure. The "chatterbox" sometimes works, but mostly our hearing is so fried from rock 'n roll we
    can't hear it. Seems to me, having a zone going helps, but ear-fry when you do find the valve occurs. This is a good reason for the naysayers who
    don't do simple as-builts to grow up. Good luck!

    Messages: 18,668

    Are you hooking to the individual zone wires or the common? Did you dig down where your null ended? I don't see your experience level with the 521 mentioned but in the beginning for a new 521 user you need to do a lot of digging so that you can learn what you are hearing.The most difficult part is following bends. One trick I use to flush difficult valves is to follow the zone wire as far as i can go while marking with flags. Then I go back and hook the ground to the zone wire and my red lead to the common and follow my path. In theory you should get no sound UNTIL you pass that zone valve which means it just before the sound started. The 521 is a great tool. Just got to trust it sometimes when your Norwegian mind tells you otherwise.
  4. jcom

    jcom LawnSite Senior Member
    Messages: 791

    Thanks guys,

    I am using the ground probe and the field wire. Nothing on the common. The common was still hooked up to the controller.

    The wire I separated was in a box where the cables were spliced together. Then hooked the red to the one I separated. And the black to ground stake.

    I have only used the 521 three times before. All were tracking our boring rods and a fish tape. And successful. No experience with wire.


    Messages: 18,668

    It definitely takes practice. It is the one tool where you build on your successes.
  6. txgrassguy

    txgrassguy LawnSite Gold Member
    Messages: 3,083

    I use the ground off of the building when tracing with my 521 where ever possible.
    Sporadic null readings will occur with the ground probe, especially in soils which have layering like when the home owner goes cheap on the topsoil and it is shallow.
    If you cannot find a common ground from the residence use a 1/2" to 3/4" copper rod about two feet long as a ground and pound this into the soil at least a foot.
    Stay away from any type of iron rod like rebar or a large spike as oxidation on the iron will also cause fluctuations in the 521 resulting in a false null.
    One other thing to remember about the 521, the capacitor in the transmitting unit (if you ever opened one up is is about the size of a golf ball) is prone to cracking, especially if the unit is either old or has seen life as a "loaner".
    What happens here is that the crack will result in an intermittent grounding through the 521 housing itself and will weaken the null reading resulting in false nulls as well. The easiest way to determine this is if you get a minor tingling in your fingers if you grab the box once the power is on. A really bad short will zap the living crap out of your hand.

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