Thursday, August 5, 2010

How To Find Underground Wires & Valves Using Greenlee 521A

1) Headset
2) Ground Stake
3) Transmitter
4) Receiver
5) Carrying Case
6) Black Lead
7) Red Lead
8) Selector Knob
9) ON/OFF Switch
10) Battery Cover

Batteries (included)
• Transmitter: Qty 8 - "D" batteries
• Receiver: Qty 1 - 9v alkaline battery

Note: The transmitter produces high voltage. Turn the transmitter off before handling the output leads. Disconnect all wires from the controller when fault locating. Turn the selector knob to the BATTERY TEST position. The meter should read between 8 and 10.

Before starting, you must ensure the transmitter is set up properly.

IMPORTANT: To ensure that the 521A transmitter is producing optimum signal, connect the red and black leads together and turn the unit on. Turn the selector knob to position #5. The meter needle should rise to at least a 10 reading.

1. With the transmitter off, connect the red lead to the wire to be located and the black lead to a good earth ground with the stake provided. (Refer to Figure 1). If the clock is indoors, the earth ground stake MUST be grounded at the point where the wires exit the building. It might require running a length of wire to the
outside. Do not use a common ground inside (i.e., electrical or water pipe).

2. Now turn the transmitter on and start rotating the selector knob clockwise.
Once you leave the BATTERY TEST position and go to #1, the meter needle will fall off to near zero. As you increase the output, the needle will rise slightly with each advancement. Stop when the meter reads between 4 and 8. The transmitter is now set for maximum efficiency for this job. If a reading of 4 is not obtainable, you may not have enough of a ground fault to locate the wire.

Soil condition can also affect the efficiency of the unit. Moisture is a good conductor, so the wetter the soil, the better. In dry or sandy conditions you may experience signal loss. Add some water near the ground stake to improve results.

3. Plug the headset into the receiver if desired, turn it on and point the antenna or probe end at the transmitter. A pulsing tone should be heard through the headset and an indication should register on the receiver meter.


Locating Wire Path
With the probe pointed toward the ground, walk completely around the transmitter location. An absence of tone or null will be detected directly over the path of the wire. Movement to either side will cause the volume of tone signal intensity to increase. Follow the null to determine the wire path. (Refer to Figure 2.)

Finding Wire Breaks and Nicks
When attempting to find breaks and nicks, you should decrease the sensitivity of the receiver when pointing it off to either side of the null. You will be able to notice the change in signal intensity immediately. Do not allow the meter to peg or go above 10. This will greatly help in the fault locating process.
Note: The wire must have a path to ground to be successfully located. These paths exist in a great majority of all direct buried wires due to insulation imperfections, nicks, and bad splices. If not, create one by grounding the remote end.
• The end of a cut or broken wire can be located by following the path until the null disappears and gives way to a hot spot. Beyond the hot spot, no null can be detected. Back up until the null is detected, and this will be the approximate end of the broken wire. (Refer to Figure 3.)
• Larger nicks in the wire can be located in almost the same way as locating opens. Follow the null and strong signal along the sides of the wire until the signal becomes very weak along the sides of the null. This will occur within a relatively short distance. The transmitted signal bleeds to ground at the nick and then wants to return to the ground stake along the outside of the wire itself. The majority of signals will stop at the nick indicated by the low receiver reading just beyond the nick. (Refer to Figure 4.)
• To more accurately define the location of an open or larger nick (ground fault), position the receiver tip on the ground near the point where the last strong signal was detected along the side of the path. The receiver tip should be pointing at the ground and be approximately 6 inches to either side from the null. Because you are so much closer to the path, the sensitivity knob must be adjusted down until the meter reads just below 10.

While maintaining the 6-inch distance from the null, move the receiver down the line, paying close attention to the meter reading. Once you pass the open or nick, the meter will fall off rapidly.

Determining Depth of Wire
To determine the depth of the wire, first mark the ground directly over the path. Turn the receiver sideways to the path, and tip it 45 degrees. Move the receiver away from the path, maintaining the 45-degree tip until a null is detected. Mark this spot. The depth is the distance between the two marks. (Refer to Figure 5.)

Two-Step Solenoid Valve Locating Process
Solenoid valves can easily be located provided all the wires leading to them are intact and the solenoid itself is still good.
Step 1. Start at the clock. Connect the red transmitter lead to the station wire leading to the subject valve, and connect the black lead to earth ground. Turn the transmitter on, adjust the output to the highest level, assemble the receiver, locate the path, and start tracing the wire following the null. The null will be present until you pass over a solenoid valve, and then the signal will become extremely strong. Mark this spot. Check around this hot spot for a null leaving the area. If the null continues, follow it and mark any additional hot spots. (Refer to Figure 6.) If only one hot spot or valve is located, it will be the valve in question.
Step 2. If more than one hot spot is found, mark them and return to the transmitter and turn it off. Lift the black lead from the ground stake and connect it to the common wire. Turn the transmitter on, set the selector knob to the highest reading, and return to the first hot spot with the receiver. Touch the tip of the receiver antenna to the ground in the center of the first hot spot and set the sensitivity knob to read near mid-scale. Now go to the second spot and without touching the sensitivity knob, check the strength of the signal at each hot spot and determine which, out of all of them, is the strongest signal. This is the valve for the station wire you are connected to.

Greenlee 521A Maintenance

Battery Replacement
1. Turn the unit off.
2. Remove the battery cover.
3. Replace the batteries (observe polarity).
4. Replace the battery cover.

Periodically wipe with a damp cloth and mild detergent; do not use abrasives or solvents.

Questions? Leave them below. Thanks!