When Finding Faults is A Good Thing
The year is 1971, and Bob Dobson has just completed the installation of a $37,000 irrigation system at a condominium. The client wants to see the system run prior to handing over the check. But there’s a delay, because a well needs to be activated before the system can be run. During the delay, an electrician came and trenched some wiring into the property, breaking the wiring in five or six places.
“He repaired it, but when we went to demonstrate the system to the client, only three of the 30 irrigation zones turned on,” recalls Dobson. “We spent the better part of two days there, trying to find the problem, but we just couldn’t.” Dobson knew there had to be a better way than just digging up the most likely suspects and hoping to find the fault, so he called his electrical supply houses.
“They put me in touch with a company that sells wire scopes and fault finders,” he said. “The company rep offered to come down and find our problem, on one condition: if he found it, we’d buy his equipment.” Out of options, Dobson agreed, and 20 minutes after the rep arrived, he found the broken wire.
The system was fixed, the client wrote a check and, being a man of his word, Dobson bought the wire scope. At the time, he thought he would have very little use for this fancy new gadget. “I have to tell you, it was the best money we ever invested. We ended up buying two more of the same scopes, and had both of them, up until two years ago,” he said.
Now, Dobson’s crews at Middletown Sprinkler Company in Port Monmouth, New Jersey, use fault finding equipment every day. It’s a no-brainer for him, but is fault-finding equipment a good purchase for your business? If you’re planning to repair irrigation systems on a regular basis, the answer is probably yes.
The first item you should probably look into is a multimeter, a basic electrician’s tool for measuring voltage, amperage and resistance (ohms). A multimeter can be used to check an irrigation system’s wiring at the controller. This is where Charles Doll, owner of Aqua Doc Irrigation in Charleston, South Carolina, starts his diagnostic work.
The multimeter usually comes with two prongs, which can be touched to the wire you want to read and the common wire (usually colored white). Instead of a prong, some models come with a clamp, which can be closed around whatever wire you want to test.
“The first thing I do is test all the zones, measure their ohms, and see if they have the correct readings,” he said. “I’m looking for a number between 26 and 60 on each zone. Higher than that, and there’s probably a short circuit; lower than that, and there’s probably a bad solenoid.” If there are no ohms at all, it’s likely a break in the wire.
Once you know what kind of problem you’re looking for, you still have to find where it’s located. The problem could still be anywhere along the wire, or in any of the valve boxes. At this point, Doll pulls out his wire and valve locator. It has black and red leads just like a multimeter, but it also has a wand, and it sends out a signal through the line, which the wand can read.
In the case of a break, the red wire is hooked into the problem zone, and the black wire is grounded to the earth with a grounding rod. The device then sends out a signal through the problem wire. The wand interprets that signal in either ‘null’ mode, meaning that there will be no sound when it’s pointed at the wire, or ‘peak’ mode, where there will only be a signal when it’s pointed at the wire.
Doll follows the null signal until he reaches the end of the wire. “When you reach the end of the wire, one of two things will happen,” he said. “It’ll emit really loud beeps to signal that you’re at the end of the wire, or the signal is going to disappear entirely.” That’s where you start digging.
If the problem is a bad solenoid, the signal will disappear— just like a broken wire—or it will ring out loud, if it isn’t completely dead. When he’s trying to trace a short circuit, Doll hooks the black wire into the common wire, rather than into the ground, and follows the same procedure. “I’ll follow the null signal, and once I get over the short, it will ring out louder,” he said.
Sometimes, the problem won’t be with just one zone, but with several. This could be the result of several different issues, or it could mean that there’s a fault in the common wire. “Very often, when there’s a problem with the common wire, all the zones after the fault location will be impacted,” said Dobson. “Once we’ve determined whether it’s the common wire or the hot wire, we break out the fault finder, also known as a pulser.”
Where the wire and valve locator sends out a continuous signal, the pulser sends out surges of energy. These high-voltage, lower-amperage signals race down the wire, and where there’s a fault, the surge will leak to the ground. The fault finder looks like one side of a walker, with two spikes on the end, and a readout on top.
“The two probes go into the ground, and they measure the current coming back, that causes the needle to swing in the direction of the leakage,” said Dobson. “So we’ll follow along the wire line that we’ve marked out using the wire scope, and take readings. The needle will continually swing in one direction, until we go past the fault.”
Once the probes are put in past the fault, the needle will swing back in the other direction. By going back and forth along the path of the wire until the needle doesn’t move, you can locate the problem. “Then, to pinpoint it, we turn the fault finder 90 degrees and repeat the process, to make sure that we are directly over the top of the fault,” Dobson said. “It basically creates a crosshair in the ground over the problem.”
So what’s the practical difference between a pulser and a wire and valve locator? Dobson says that it’s a question of precision. “Depending on the manufacturer, you can get a change in signal from a wire tracker, and if you’re lucky, it will give you a general area for where the problem is. The fault finder is a lot more precise, and 90 percent of the time, it will put you right on top of it.”
Using the right equipment saves a considerable amount of time; how much depends on the size of the property, the length of the wire runs, and how precise your equipment is. Doll estimates that he’s 200 percent more efficient with his equipment than without it. As for Dobson, he says that most of the time, they locate faults within an hour. On a commercial property the size of a ball field, it takes about a half hour to track the wire path, and maybe 15 or 20 minutes more to pinpoint the break.
Some properties are more difficult than others, because other electrical lines buried in the ground can interfere with the signal. An analog wire tracker is picking up electrical signals, and any other sources of power in the ground will set it off.
According to Bruce Nelson, president of Armada Technologies LLC, in Caledonia, Michigan, there are digital models which can help cut through the noise. “A digital locator eliminates the contractor’s number-one irritant when finding wire breaks, and that is AC electrical interference coming through the receiver,” he said.
There are a handful of other features that you can look for when considering fault-finding equipment. Some models offer both null and peak signaling; others only offer one or the other. Some have variable power output, and a little extra power can be useful when tracking a deeply buried wire, or a particularly long wire run.
Using tools that are more powerful and more sensitive is particularly important when you’re dealing with a 2-wire irrigation system. In a 2-wire system, the path runs from decoder to decoder, and at each decoder, a wire branches off to the solenoid. This design can make finding hidden or buried valve boxes a hassle, because if the decoder isn’t sending power to the solenoid, there isn’t a signal to follow. As such, you may not even realize you’ve just passed over a decoder.
“Literally, at every Irrigation Association show I go to, someone will come up to me and ask if we have a locator that will find decoders,” said Nelson. “We think we’ve come up with a viable solution, and it’s entirely a matter of sensitivity.”
There are times when being able to detect that interference can be useful, believe it or not. Let’s say you’re installing a French drain along a property, from the side of a building, all the way to the ditch alongside a road. You’ve done your due diligence and put in your call to 811, so a team has come along and marked the locations of public utilities. You’re clear to dig, right?
Wrong. There are still private utility lines to consider. Wires can be buried in the ground for pools, fire pits and electric dog fences, just to name a few. The local government won’t mark them, but you’ll pay for breaking them. Checking for signals in any ground you’re planning to disturb can help avoid unwelcome surprises.
What kind of fault-finding equipment will best suit your business depends on how much time you spend finding and fixing problems with wires and solenoids. If you have detailed irrigation schematics for all your properties, and this problem only crops up once every few months, you might want to see if you can rent this equipment when needed.
If this problem crops up every week, the savings in labor costs alone will likely pay for the equipment, not counting the extra time that quick troubleshooting will create in your scheduling. If you offer landscape lighting as one of your services, or want to doublecheck for wires before you dig, your investment in this equipment goes that much further.
When you start adding a new service to your landscape business, there’s a lot to learn, and it can be easy to stick to a certain way of doing things, just because it’s what you know. However, learning new techniques, and doing research on what’s available in your field, can yield massive dividends by making your operations more efficient.
It seems like everybody these days is struggling to keep on top of their workloads, and finding the labor to do it. In a market like this, anything that can save you time is worth its weight in gold. So, do yourself a favor; give fault finding equipment a good hard look— go out and try it yourself. You may end up wondering how you ever did your job without it.