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Discussion Starter · #1 ·
I have a new customer that has been having solenoids go out on him. 4 in the last 9 mos. since installation. Installer will not return phone calls.

Hunter system. SRV valves. Cable used appears to be phone or communications cable. Blue or green casing with very small wires inside.
Suspecting the cable to be the problem, I checked for 24v outside. It is running about 26v. Cable is buried for about 30 feet out of the building.

When checking for resistance, can I take off the valve wire at the controller and read through the solenoid or does it need to be isolated completely? I get a reading of 6 on the 10X scale with the solenoid still in the circuit. Checking between zone wire and common. If 6 is a good number, there would be high current going to the solenoid if my figuring is correct.

Thanks in advance for the update and assist.

John :rolleyes:
 

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Are the solenoids themselves testing as bad? After you removed them? Their life shouldn't relate to the wiring used to connect them. (even if it is undersized) If you got a 60 ohm solenoid resistance reading, that would probably be acceptable. And you do want to remove the zone wire from the controller before you test, so there's no confusion. The actual AC solenoid resistance at 60 Hz will be greater than what you read with the multimeter. If that suspect cable contains stranded wire, you will want to replace it. If it's only 30 feet, I think I'd replace it in any event.
 

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I would change the wiring especially since it sounds to be thermostat wire at best, and probably speaker wire. Use a minimum of 18ga. For 30' it won't take that long to rebury it.

As for the solenoids - are they the old style Hunter solenoids that used to swell and break the case? The contractor may have had old stock in the truck and found a place to get rid of them. Take them to a Hunter distributor and have them check them out.

As for measuring resistance to a solenoid, you are looking for a reading that is way out of range. Solenoids may have a resistance reading of 20 to 60 ohms depending on manufacturer, and the distance to the valve, and the size of wire used. What you are looking for is one that reads significantly higher or lower than the rest.

I would check to see about the solenoids first. 4 in 9 months is a little excessive. Actually a lot excessive.

Jerry
 

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Discussion Starter · #4 ·
Thanks for the help.

I did have the wire off the controller but not separated from the solenoid. Measured between wire from controller and common.

I have only replaced one solenoid as the installer replaced the others but apparently got tired of warranty work! I am trying to find the reason for all the failures in a short period of time and is the reason I suspected the cable.

Cable is buried under a sidewalk as well. It is not stranded cable but conductors are very small. I think the small wire has too much resistance and hence would require more current than the solenoids are rated for. After many months of use, they just fail. Any help with this perception is appreciated.

Thanks again,

John
 

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Undersized wire is about as likely to cause solenoid failure as undersized pipe is to cause sprinkler head failure. Poor operation, yes. Failure, no. There are bad batches of stuff out there, solenoids included. I had some mysterious solenoid malfunctions on some Irritrol/Hardie/Richdel valves, but only on the anti-syphon ones. Turns out that there is a magnetic core pressed into the hollow tube of the solenoid, and there was an air space above it, into which water could somehow penetrate, and freeze, even after thorough winterizing. The result of the freezing was to push the core downward a bit, and the following spring, the solenoid plunger could not raise high enough to open the valve. Valves in underground boxes escaped freezing problems.

As long as the smaller wire is intact, it is only a resistance, that would reduce the voltage seen by the solenoid. Since most solenoids have positive operation at 20 volts, you can afford to lose a bit (not that you want to) through the wiring. Remember that the manufacturers allow for 800 foot runs of 18 gauge wire to a solenoid.
 

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If I were tackling this problem, and if this is just happening to one valve, one zone, one wire within the cable, then I’d test the non-operative solenoid with a different wire within the cable. You could even switch out the ground wire, if you suspect it – which could cause multiple zone failures.

The resistance from a thirty foot run of 18 gauge solid copper should be negligible, unless if physical damage has occurred. You stated that you’re showing 26 volts, which is fine, but if for some reason the supplied current from the controller is not enough to latch and hold the solenoid then this voltage reading isn’t going to mean a whole lot. If there is a current leak through the wiring – such as a nick or cut in the insulation, or maybe some connections getting soaked or underwater, then you could show 26 volts but not have enough current to activate the solenoid. A different controller with perhaps a little more output current per zone possibly could keep things ticking, up to a point of course, and you'd never know that there was a problem.
 

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Does the "bad" solenoid still work if you take it to the controller and touch the solenoid wires directly to the common and station terminals? If it does, maybe the solenoid isn't bad, if it doesn't, then you need a new one. I still wouldn't blame a wire sizing problem for solenoid failure.
 

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Discussion Starter · #8 ·
Wire size can have a direct impact on solenoid life. If current is too high, it will burn out the solenoid. Unlike water and pipe size, which does not have a relationship with heat. If a sprinkler head does not have enough volume/pressure, it will not function properly, unlike an electrical solenoid which if not given enough volts/watts/ or high current will fail eventually.
Some troubleshooting needs to be between the ears and not just on electrical hypothesis!

Thanks all for the help as the problem is ongoing as the resistance is within specs. Four valves in one season is just not in my realm of normal. When I have it tracked down, I will let you know.

John :waving:
 

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Just one other thought, this is a new account for you, correct? Was the controller left on and cycling last winter? You mentioned heat, and that reminded me of a few older systems that I have seen when the controller isn't turned off for the winter, the solenoids continue to run, but w/ no water flowing over the plunger, they over heat and are bad in the spring. WM solenoids are real good at this, and they become magnatized to the point that they will not release the plunger when the solenoid is turned back off. You can tap them slightly, and they reset. Sometimes the pressure of the next valve opening or closing will make the plunger fall and you don't even notice the zone is sticking for a long time. You didn't mention brand, there have been some bad runs of solenoids in the last few years too.
 

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Discussion Starter · #10 ·
This is a new account. I don't know if the controller was left on. Very possible knowing what I know now! That is the one logical cause for all the failures.

The system is Hunter all the way to the valves and then Maxi Paws and 1804 for heads.

Thanks for the tip.

John :rolleyes:
 

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jcom said:
This is a new account. I don't know if the controller was left on. Very possible knowing what I know now! That is the one logical cause for all the failures.

The system is Hunter all the way to the valves and then Maxi Paws and 1804 for heads.

Thanks for the tip.

John :rolleyes:
The Hunter solenoids are sealed (rubber on the bottom, plunger hole doesn't see any water, I don't think), but if the wires are black instead of red, you got the old solenoids they re-vamped because of a LOT of problems. Not only did some of them just quit, but some of them actually separated from their casings too.
 

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jcom said:
Wire size can have a direct impact on solenoid life. If current is too high, it will burn out the solenoid.
Uhhh, no. Not from a properly functioning controller and solenoid. There is no such thing as a solenoid burning out from receiving too little voltage. They may fail to operate, but burn out? It doesn't follow.

The controller supplies voltage. The solenoid (and wiring) present a resistance. The current is like the caboose that follows the voltage-resistance train. (current equals voltage divided by resistance) And a length of undersized wire is just some added resistance to the equation, with reduced solenoid voltage (and current) as a result.

Wintertime controller operation doesn't do any good for the valves, although it usually takes a circuit being energized for days on end to finally do in the solenoid. The water that's normally in the valve does seem to provide some necessary cooling on some older solenoids.
 

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Well, I'm not sure if I'd say that there is no such thing as a solenoid burning out from not receiving enough voltage, but in this case where we're dealing with 24 volts at small current levels, this isn't likely to happen too often.

However, heat is a physical property caused by the resistance within a device to voltage and current flow. Electro mechanical devices can be burned out by low voltages falling below their nominal operating characteristics. Such is the reason why brown outs are serious business to appliances and mechinical devices. A electo mechanical device may not operate because of a low voltage, but it will continue to draw current and to build up heat until it burns out. Can happen.

And for whatever it's worth, it has been written that valves should be briefly cycled on and off during the winter after the system has been blown out and winterized. The idea being that the heat from the solenoid helps to evaporate any moisture within the valve. I haven't done this, but some people profess to it.
 

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Solenoids aren't motors, so the same kind of heat buildup from low voltage non-operation would not apply. Think of how many melted solenoids you've seen, and then ask yourself how many of them were at the end of a substandard cable. And think of how many instances of bad wiring you've seen, and how many burned out solenoids showed up there. I don't see any connection.

This thread illustrates some of the same slightly-unclear-on-the-concept thinking that we all see when some homeowner insists that connecting his portable sprinklers to half inch hoses makes them work better than if they were using three quarter inch hoses. "But the water runs faster through it!" they claim, unaware of what anyone can read from a friction loss table. No wire size can cause higher-than-usual current.

I think in this system's problem(s) it's either wintertime operation or faulty solenoid construction. I occasionally see solenoids fried from lightning striking the lawn, but I doubt that the solid-state controllers of today would survive that sort of thing.
 

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Discussion Starter · #15 ·
Hey guys,

Where am I wrong in my thinking. It would seem there are some disagreements to my ideas.

I first checked for voltage drop due to either incoming low voltage at the controller or some other factor at the solenoid. If I had encountered low voltage it would have meant much higher current, aka "heat", required for the solenoid to operate. Which in turn would cause rapid solenoid failure which is what I have been told has occurred. I will monitor it now as I have much more info that when I first embarked on this snafu. Too say that small conductor will not cause the above is not going to be very accurate as it is certainly possible. Agreed, my voltage has been up to specs and resistance also, but my initial check was for voltage and consequently higher current than the solenoids would funtion with for the long term.

The owner is not available now so I cannot confirm winter operation nor the condition of the other solenoids as they were turned in to the initial installer earlier this spring.

Too many facts and not enough information! :)


Thanks for all the input.

John
 

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jcom said:
If I had encountered low voltage it would have meant much higher current
Uhh, once again, no. The solenoid does not magically suck extra power from the wiring if the voltage is less than normal. For the low-voltage problems that motors encounter, they would suffer when low voltage prevents the motor from starting to turn, and in failing to turn, fail to create the magnetic field that affects the electrical resistance of the motor. In those circumstances, overheating is a real possibility. A solenoid is just a coil of wire around a metal core. No rotating parts, and no equivalent magnetic field situation.

Unless you have taken a resistance measurement of the cable in this system, and found an excess resistance, I wouldn't worry too much about it. Suspect crappy solenoids instead. There are countless rock-solid Rainbird RC electromechanical controllers out there with wiring harnesses of 'undersized' 22 gauge wire in them, and never a problem.
 

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Discussion Starter · #17 ·
My thinking: The solenoid needs X number of watts to function or activate. If the voltage is low, then more current would be needed. This would also be the case if the resistance was too high. If the X number is not available with design voltage, then the current would surpass designed capacity.

I am still learning all the ins and outs but OHMS Law is a treasure.

I really appreciate all the info and value all of your inputs.

John :waving:
 

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jcom said:
My thinking: The solenoid needs X number of watts to function or activate. If the voltage is low, then more current would be needed. This would also be the case if the resistance was too high. If the X number is not available with design voltage, then the current would surpass designed capacity.
One more time, no. Read the solenoid manufacturer's data, and you might find a 'minimum voltage needed to operate' number. Voltage. These devices run on voltage. Give them sufficient voltage, and they will work. The solenoid has a resistance (in purely electrical terms, you would call it a 'reactance' which is a term that takes coils [inductance] and capacitors [capacitance] into account) and when you apply a voltage to a resistance, the result is a current. You are not applying a current. You are applying a voltage.

You keep stating the idea that the solenoid is going to somehow magically draw extra current if the voltage is too low. If you can find that in Ohm's law, quit your day job and apply for a government research grant. Ever heard of a sprinkler head drawing extra flow when the pressure is too low? Try to find a performance chart showing that. Same concept.

I recall the first time I got an estimate for wiring a building I was leasing, and I thought some reserve capacity would be a good idea. So I sketched some thirty amp circuits feeding the wall outlets. "Uhhhh, no," the electrician pointed out patiently to yet another dumb plumber, "You can't have a 15-amp-rated receptacle on a 30 amp circuit."

So maybe it's a good idea after all that we run these sprinkler systems from plug-in class 2 stepdown transformers.
 
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