Good morning, I'm Jim Carefoot with Armada Technologies and welcome to our Find-It- Fix-it Friday, 30 minute sessions we do
every Friday on some topic of interest for testing and the green industry in
particular. Today our topic is differences between troubleshooting
multi-wire irrigation systems and 2-wire. We've had a lot of questions
recently about 2-wire troubleshooting. We have a little training course that we
do on troubleshooting 2-wire but today we're just going to do 30 minutes, kind of
blow through it and talk about the differences because we're test people
and it's about what kind of test equipment and process is different
between these two. So we have everyone muted and because of the number of people on here. You're welcome to use your little side control panel on your screen
to send me a question by message box. I can handle that at the end and if you
raise your hand at the end using the little control panel, I can try to unmute
people and answer questions. We'll keep it under 30; everybody's
time is valuable.
So with that, I should also mention, if you
can see me in a little webinar photo thing in the corner there, you
don't need to watch me, you can always minimize that so you can see the
slideshow which is the important part. We're just going to go through some
slides and narrate it a little bit today. I think that all of you are probably
familiar with the two classic types of irrigation systems. The multi wire, what I
call a conventional irrigation system that people have used for a long time,
and the 2-wire which is a somewhat more complex and bigger type of a system
that is more common these days in certain applications where it's
economical like golf courses, big parks, business parks, that sort of thing where
multi-wire starts to struggle to get it the same kind of size and reach. The
multi-wire application you can see on this slide here, multi wire control or
what I call a wire per valve. Each of the valves in the field is
remotely controlled, has one wire running to it, and there's a common wire that connects them all together.
The multi wire controller lets water into
the zones by applying 24 volts on the appropriate wire; it causes the valve
solenoid to pull and open the diaphragm and water flows. It's something I think
probably most folks are familiar with, although we have a little class that we
do too on troubleshooting this kind of system. A 2-wire system, as you see here, is different primarily in the fact that it uses one control cable that just has two
wires in it. We're literally talking about a computer-controlled local area
network.
The 2-wire controller here is a smart system that has all these slaves
that we call decoders that are in the valve boxes and these decoders are
actually the ones that activate the valve solenoid, so a very different kind
of a structure. I've got a couple of diagrams to help illustrate the difference when
you get into the field. One control cable, a long string of decoders that fire the
valves based on their commands from the 2-wire controller. All of the stuff,
of course, is underground or flush- level valve boxes and you need to find
both those paths and the valve boxes in order to do your
troubleshooting. This diagram helps illustrate the difference between the
wiring in these two systems which makes a big difference in how your
troubleshooting goes too. In a star or home-run conventional multi wire system, you've got a common running to every valve in
the system and you've got a single wire running to each of the valves
independently so that they're fired with 24 volts.
They're fanned out, kind
of spread out, what I would call a star configuration or all the wires home-run.
In a daisy chain arrangement, in a 2- wire control system, you have one control
cable that just runs from valve box to valve box and depending on how things
are laid out these wires may be operated in kind of a loop or a Y or something
but it's really basically, a chain of decoders with valves. It's topology or
physical layout is quite a bit different, as you can see in the diagram
there that illustrates the same property done with two different types of systems.
So whether you're doing one or the other, whether it's 2-wire or whether it's a
conventional system, you've got some of the same kinds of problems you have to
solve.
Is the system dead? Why is a system dead? Is the controller the
problem? We always say in the troubleshooting and with this stuff, and we
have a chart to illustrate this a little bit later, you always start out at the
source of the power and work toward the field. You're always looking first at
the controller; if somebody's popped the circuit breaker and the controller is
dead or someone's got a rain sensor unplugged, who knows, but the controller
can stop working. These are all kinds of things that you need to do that's
in common with any irrigation system.
Faults on the buried wire, that's
one of our four phases is tracking and finding faults and valve boxes. Locating
where all these things are is the beginning of your troubleshooting
once you get away from the controller. So, same old problems. I've made a bullet
list here of the differences between a multi-wire and a 2-wire system. I kind of
listed the multi-wire and then the 2- wire. I won't read the list of bullets but
you kind of get the idea, the difference between them, that the 2-wire system
has a single cable with two wires in it for control and power that daisy chains
all the valve boxes together whereas the multi wire, which you're more
familiar with probably, has a wire per valve with the common wire.
So that's a
pretty fat bunch of wires. The multi wire turns on valves with a shot of 24 volts
AC and the 2-wire systems commonly have something over 30 volts running on
their control cable and that voltage is led out to the valve to close
the valve based on the command to a decoder. So literally when you start
working on 2-wire systems, you're kind of becoming a computer technician here
in having to troubleshoot the computer system and data communications in the
slaves. So in that regard, it's somewhat different. One thing I should mention as
a difference between the two systems too is that the 30-some volts that's on the
control cable is there 24/7. It's there constantly and what that means is that
the splices become more critical. The splices that are powered constantly get wet and there's moisture in the air, that encourages corrosion with the
copper. So what you have to do is use a very high-grade DBY-type splice when you're doing the wiring between the control cable and the valves.
That's the main difference because one of the biggest failure modes of the 2-wire system is exposed copper or damage to the splices and the valve box.
There's a list of these things; we'll be posting a recording of this slideshow
and discussion this morning and on our YouTube later on today so you'll be able
to see this, you don't have to try to screen capture or do something if you
wanted that list.
The names of people who make 2-wire systems are pretty much
the names that you see in the regular irrigation world for valves and
controllers and all sorts of things. Hunter, Toro, Baseline, Rainbird, all our
usual friends are there and each one of these systems is a little different.
They're all smart systems and they have to drive their own decoders typically so
you have to know what kind of system you're in.
You don't have to take the
multi-day training class that these guys offer, necessarily, in decoders to do a
little troubleshooting. You can go down to and sit in a Hunter class for three
days and they'll tell you how to program it, how to troubleshoot, how to design the
system, everything. We do a little class in troubleshooting that takes less
than an hour and today we're doing this in 30 minutes and we're not detailed
troubleshooting, but it's the 80/20 rule; you have to get
a leg up on this thing.
So as with any kinds of the field systems like this the
process for doing troubleshooting in a 2-wire controller is start at the
power source and work towards the field, even in a 2-wire system. The
difference in a 2-wire system is that the controller is much more
sophisticated than the basic clock that you'll see, even in more recent model
versions of a conventional irrigation system. It's pretty smart; it has built-in
diagnostics so when we tell people to get started in troubleshooting this thing,
always start with the controller and let the controller tell you if it
thinks something is wrong because it may identify things for you. It may tell you
what zone and valve has got a problem, it may tell you there's an overcurrent situation. It's a good
beginning with a 2-wire system.
Working your way out toward the field
wire, you need to disconnect the cable, do the resistance measurements, that kind of
stuff. That'll be common to all of these sort of systems. Check each wire to ground. You want to have a good
half mega-ohm, that kind of stuff you're looking for, places where there's a
leakage to ground, a bad splice in water, a nicked cable, that kind of thing. You need to find the decoders and one of the main differences between the
2-wire system and a conventional system when you're doing troubleshooting is
that you cannot find the valve boxes with a locator.
Our locators are called
wire and valve locators but that is true in systems where the valve solenoids
are wired directly to the system, but in a 2-wire system you cannot find the
valve box because it's hidden behind the decoder. I have a little diagram to
illustrate that later when we get into locating tips. The valve solenoids,
once you find the valve box that's where all your issues probably typically are.
You've got a bad splice, you've got a solenoid that's gone bad, you have a
valve that's got a torn diaphragm, all that stuff all that treasure is in the
box so you still have to have a way to find the valve boxes.
We're test
equipment folks so that's we're focusing on here, the things that you can still
use that you've always used with systems that hopefully you have. For example, an
electrical meter. I don't care if it's a Harbor Freight $10
special electrical meter, it's a good thing to have. You're going to have to check
voltages and resistance anytime you're doing troubleshooting. Somebody
with you or in your vehicle has got to have a meter. A solenoid activator is
great, good for conventional systems but it allows you to test the solenoid
inside the valve box to figure out whether you've got a bad decoder or bad
solenoid, so still useful.
Wire and valve locators: no matter what you do you still
have to know where stuff is buried and that means following the mean path of
the cable. So you've got one of those, you have access to one, you can rent one,
you're good. Pretty important. A ground fault locator
is another big deal because some of the damage that occurs in the field
is damage to cables, besides having a slice issue and you can
even find a wet splice using this, actually.
It'll lead you to a place where the
installation has been nicked or the wires have been cut. Great thing, works with all
these systems. When we get the 2- wire systems there are a couple extra
items you need to know about. I've got a picture of some of these here as
we go forward, a milliamp clamp meter is something that
critical especially since we're really concerned about the splices in the
system. We need to be able to find out what's going on in the system's control
wiring without opening splices. So a clamp meter is the right answer here
because it clips over the wire without having to do any kind of wire skinning
or opening of slices. Furthermore, it has to be a very sensitive
RMS clamp meter that allows you to read the tiny currents that are flowing
through these 2-wire systems and by tiny I mean, every one of these decoders
can consume as little as a milliamp or even less than a milliamp. So you've
got a chain of 100 decoders and valve boxes out there being driven by the controller,
that's 100 milli amperes so that's a pretty respectable current, but you need
to be able to go from box to box and read the decrease in current as you get
further into the field or find the places where gross currents are sliding
to ground because of a wet splice or a cut cable.
Anyway, this meter becomes a critical factor and it's recommended by the IA
and this kind of a test meter is also recommended by
manufacturers like Rainbird and Hunter.
So, a good thing to have if you're
going to do this stuff. A 24 volt power source: now, what you'll
also hear from the 2-wire vendors, and it's an excellent idea, is to
have a power source there so you can power the field wire up
separately from the controller. You're disconnecting from the controller anyway
to do locating, to do some resistance checks, but if you want to get out there
and start feeding some current and voltage down the wire to help isolate
problems, putting your own 24 volt power supply on the line is a good idea. You can get these things for less than $20; I've got a picture of one later.
It let's you do troubleshooting independently from the controller
because if the system has kind of gone really flaky, the controller
will let go anyway and it won't supply power and you have to have power on the
cable to troubleshoot.
Another item that we've got that I'll touch on the
end is wire radar. Since we can't find valve boxes is using a locator in the same
way we used to, something that could be pretty handy, we've had some customers
that have had good luck with this, is use a TDR, time-domain reflectometer or a wire
radar, that pings down the wire and tells you distances to faults including
splices, even good splices. So it helps you find valve boxes. All these things are time savers. Some of these things you could
probably figure out with a shovel and a backhoe or you know, a little meter
after a while but every one of these things is going to help you with your
troubleshooting speed.
Among the tools, little diagram here, the tools that
you've got that you might have used for a while, a locator or the ground fault
finder like that a-frame on the right. Our Pro800D is our most popular
locator now because it has wireless, connectionless tracing, it has
regular tracing, it has peak and null mode antenna switching which has some
surprising benefits. In the middle are the things that pop up
when you get into the 2-wire system and there is that the true RMS milliamp
clamp meter that I talked about. The Pro93 is our model and it is commonly
used in training, demonstration in the field for finding faults in a two wire
system without having to open up connections. Great tool. There's a
picture of the little handheld wire radar toward the bottom, another kind of
a nifty thing but it takes some doing to figure out, you have to be experienced to
know how to use it. We stole this from the cable TV business
where we sell a lot of them and very useful for those folks for finding
places where wires have been crushed and cut and the distance to them.
So the
clamp meter again, we sell several varieties of clamp meters
and the Pro93 for the two- wire is the most expensive and the
fanciest but they all work by clamping over one of the pair of wires. Now, we've
got two wires going out in the field in the two-wire system obviously, so we got
to clamp over one of them and we can read without interrupting anything
the amount of power being fed to the field through this. It can also go
back up to the controller, plug the test leads into this, and read the voltage
going into the field which is one of the first things you do. Out there,
clamping over the wire is a very good non-invasive way of finding out if the
power is flowing up from box to box down the chain as you expect it to. So
this is a good illustration of what very often happens in a basic 2-wire
system.
You've got a controller at one end and a long daisy chain of valve
boxes where the power and control signals
are dropped off in each one for the slave decoders. The controller sits
at one end and says okay, I need water valve 16, so it looks up the address,
sends a signal to the valve 16, says turn on now, the valve turns on just like it
was being powered in the conventional system, water flows. All the
programming in the 2-wire system, that sort of stuff, is done in an usual way.
Setting up a range of days and hours and that sort of thing, it's just the control
mechanism that's different and unfortunately for you that's the part you have to
solve so you become kind of an electronic technician for data
networks practically when you do this but we're usually hunting for wire
problems.
The most common problem in a situation like this is a bad
splice because of the constant power and current flowing through the system
and the corrosion mechanisms that go along with copper and other stuff; DBY
splices, just to list one manufacturer. Cable damage, cuts, skins, bad splices, bad
decoders, you'll find things out there that you're not used to seeing sometimes:
lightning protection, ground protection. Normally you shouldn't
have to worry too much about this but because of the electronics in the system
and the length of the chain, they put lightning protection in because
they're pretty easily exposed to lightning, especially golf courses and
business parts that have thousands of feet of run of this cable. So that's
what you're going to be facing. Here's a little troubleshooting diagram that we
use when we do the training on two-wires, just to give you an idea of the things that
you start out doing and it's like I said, start with the controller because
you're going from the source of the power toward the field application.
So
making sure the power is okay and things are coming out of the controller okay, that
controller thinks everything's fine, or you know it's working at least and you
get down to where you're troubleshooting the field cable. There's a little
picture there that shows that test power unit that I mentioned. You may need to
carry a big extension cord in order to get power to this little unit unless
you've got some other 20-40 volt AC signal generator but it's worthwhile
because you can put your own signal on there
that's very easy to measure and the controller doesn't have to be working. It
can be dead, it can be unhappy, it can be disconnected for safety, whatever, but you
use this little power unit to apply power to both leads of the main control
cable and it allows you to do the same measurement with the clamp meter.
Do
I have too much current flowing? Is there excess current on one side of one of the
wires and not on the other? Is there a very low current meaning I'm
probably got to cut up ahead somewhere and some of the decoders have been
isolated and they're not consuming as much power as they should? You've got a
spring of 100 valve boxes or something running down a golf course and each
of the controllers is sipping 1 milliampere a piece, that's 100 milliamperes. If you've lost 50 milliamperes you can figure, wow, it's cut probably somewhere in the middle of the chain. That's the kind of stuff
you're doing. You have to be a little bit of a detective in order to get this
stuff done. Here's just another illustration of the clamp meter in
action.
You can't use the voltage test as you can see, you should, go
to the two-wire controller. Systems vary a little bit; 32 volts, 36 volts, very
weird waveforms coming out of two wire controllers for these systems so the
true RMS meter is very important in that regard. This clamp meter that we sell, a Pro93, has a RMS voltage measuring function
which is a computing function. Hunter systems have a 1 Hertz square wave power
feed to this field which is a very odd thing. Most meters will not read that
correctly, you have to have a true RMS meter to read this correctly. It also has
a peak hold function so you can tell it to hold the maximum voltage it sees, that
way you can read the real system voltage. Very useful, important things
when you're doing this. As you go into the field, like I said, when you're
missing current or you have too much current or currents all in one wire
instead of the other, you can figure you've got faults to ground out there,
you've got cuts in the wire in one side or the other side.
Find the valve boxes, open them up, clamp the clamp meter around to see if
the currents are what you expect. We talk a little bit about this in our
training course. So that's what you end up doing and this is probably the most
important added tool when you're doing this sort of a system. Tips I want to mention when you're doing locating: remember you
cannot find a valve in a system like this because it's behind the decoder and
the trick in valve location is we're looking for the valve solenoid that
activates the valve. The signal we send out to the field with a locator
doesn't make it to the valve solenoid in this case because the decoder is
managing the valve and so the signal is blocked. You will find the path just
fine on one of these things but you will not find the valve so you need another
trick. Sometimes the valves are handy, they're just kind of along the chain. You
follow the path of the wire and you see the lids of the valve boxes.
In a lot of
places where the grass grows fast and landscape rock is used or something, they
may be covered up. You may have to poke for them, you may have to use the TDR.
Sometimes with experience you can spot the valve box because it's got an extra
a little bit of coil up a wire inside it and the supply for the splicing that's
done there, so that's another way of finding them but don't expect to find
the valve boxes using a locator the way you usually do. Another thing I
want to mention in this diagram, when you're locating a two-wire cable line you have to know the path whether you're working in this kind of system or
not. The control cable path is critical to troubleshooting because it leads you
to all your application stuff. Now, when you use a locator couple only
to one of the wires in the control cable and the other lead goes to ground just
like the most common locating application but we do not recommend that
you connect both leads of the locator across the two wires of the
control cable.
One of the reasons is that a locator, unless it's loaded down, can put out hundreds of volts and we don't want to damage any decoders that
might be sensitive to that in the system or cause the lightning protection
to activate. So you have to be a little careful when you do some locating. This
is that wire radar that I mentioned, it is a TDR in techie terms and some of you
may have used these before but this takes a little bit of experimentation to
learn how to use it well. You can see on the diagram that it sends out a
little ping and gives you a waveform trace and then it has a sliding scale
line on there to you determine how far away the echo is.
The main picture here shows a little test cable I built up that is 100 ft.
Long with a good splice at 75 ft. So I hook up the wire
radar to it and you can see the picture that it produces. I see a big upward blip
at the end which is the sign of an open circuit; a downward blip is a sign of a
short circuit. There are some little cheat cards to go with this. Then
you can see a wiggle that occurs between that big blip and where you started
which is on the left. I slide my little cursor line out there and I read
the distance. It says, Oh, 100 ft out I've got an open circuit. If
I slide my little cursor back to where the little wiggle is, I can see it's 75
ft. Almost looks like there's a splice. Pretty handy thing for being able to
locate valve boxes you can't find otherwise. With a TDR you can see
a perfectly good splice and see the distance to it. The trick is
in calibrating the correction factor for the cable on this device so that the
distance is read right. A couple more illustrations of signals, transmissions,
that we did during testing and training.
The blip is like an old-fashioned
radar or sonar system, you send a pulse up from the left and you get a blip
coming off to the right, you slide your cursor over and read the distance. If you
set the correction factor on the cable correctly, you can find this stuff. Another tool that's available and may be necessary sometimes to help find the
valve boxes, providing you don't have good diagrams of where everything is. A lot of times the valve box will be sidesteps, say 20 ft, and you can't
tell that it's off the main path because no one has a diagram that shows you
quite right. It's especially true when you inherit a system that you weren't
involved in in the beginning. So that's it, we're trying to keep it short and to the
point.
You're welcome to send me some email questions, of course, and to look at
our YouTube videos. This particular session, for those that might have missed
it or want to see it again or want to get one of the slides off it, will
be available on YouTube later today. We don't intend this to be comprehensive,
just to be an introduction. Next week, we're going to talk about
checking a conventional irrigation system just by standing at the valve box. It's especially important to people as we are coming up on the spring
season where we need to do system rehabs.
You walk out and say, okay, it's been shut
down for the season, I need to stand at the box. How do I gauge whether this
system is still basically running without even leaving the box? That's what
we're going to do next week. The week beyond that, because these automatic clamp
meters are really pretty handy electrical gadgets. We're gonna have a
little session on how to use them and how to pick the right one to use. You can find a meter like I said, Arbor Freight $10.
It's not
going to do what some of these other things do.
Chances are, you have to spend maybe $150-200 buying meter, depending on
what you're doing so we're going to talk about that. Our
YouTube page has got a bunch of stuff in it that are very useful things, over 20
videos that show you tips on locating. If you're using a locator for the first
time, you're renting one or something, we have a nice 12 minute video that talks
about how to unbox it, hook it up, how to use it,
techniques. We have shorter videos for how to find valves, various useful good
things and that's it, the Armadatech channel at YouTube. Beyond that, we also
have a little blog where we post application notes and other information. For that matter, invites to these webinar sessions can be found at the
blog that's at armadaupdate.wordpress.com.
You'll be able to see this
slide again, of course, when we post it. I can be reached,
I'm Jim Carefoot and I can be reached at jcarefoot@armadatech.com. So,
with that we are pretty much done with today's webinar. We try to always keep it
well within bounds here, everybody's busy and it's the middle of the day for some
people. I thank you and if anyone's got any questions please send me by
the message box or just drop me an email, I'd be happy to.
I very often get a
couple questions after these sessions on some particular issue. Thanks for
joining us today!.