Sprinkler valve solenoid amps?

[Dallas]

I've got a real head scratcher.



Long story short: 18 zone, 24-volt AC commercial sprinkler controller
system.



One valve on the system won't operate anymore after running fine for years.



The valve operates when connected to a battery operated testing unit.



Voltage at the controller terminal going out to the zone shows 29 volts.



The wires from the controller at the valve (guessing 200+ foot underground
run, 14 gauge wire) show 27.4 volts.



There's enough current to give you a tickle if you grab the wires.



Connect the 27.4 volts to the valve and nothing happens.





My degree was in Business so I start to get fuzzy at this point. Could one
of the wires be missing some insulation somewhere underground and drawing
off enough amperage to keep the solenoid from actuating while still showing
27.4 volts?



Is there anything that could happen to a solenoid coil that could make it
demand more current to operate?



Sadly my $30 meter doesn't have an amperage function. Would hooking the
voltmeter in series with the circuit tell me anything?



Can anyone give me a clue as to what's going on?



Dallas

 

[Dallas]

Sorry about all the extra carrage returns in that post... I really wasn't
trying to be dramatic, I cut and pasted from MS Word and that was the
result.

Dallas

 

[ampdoc]

I've got a real head scratcher.



Long story short: 18 zone, 24-volt AC commercial sprinkler controller
system.



One valve on the system won't operate anymore after running fine for
years.



The valve operates when connected to a battery operated testing unit.



Voltage at the controller terminal going out to the zone shows 29 volts.



The wires from the controller at the valve (guessing 200+ foot underground
run, 14 gauge wire) show 27.4 volts.



There's enough current to give you a tickle if you grab the wires.



Connect the 27.4 volts to the valve and nothing happens.





My degree was in Business so I start to get fuzzy at this point. Could
one of the wires be missing some insulation somewhere underground and
drawing off enough amperage to keep the solenoid from actuating while
still showing 27.4 volts?



Is there anything that could happen to a solenoid coil that could make it
demand more current to operate?



Sadly my $30 meter doesn't have an amperage function. Would hooking the
voltmeter in series with the circuit tell me anything?



Can anyone give me a clue as to what's going on?



Dallas

Loading. You are testing the wire in a no-load condition.

A nick in the wire somewhere allowing water to enter could have caused
corrosion, and made a resistor of your wire. When you check the end of it,
even with your finger, you have not applied a load to the line. Try
measuring the voltage at the valve when the wires are connected. I bet you
will find that due to resistance in the wire, you have too much voltage drop
for the valve to work.

If so, your best option is to replace the wire.

Jammy

 

[Bennett Price]

There might be a cut in the wires so that only one or two strands are
carrying the voltage. Without a load (the valve) voltage looks fine but
when the valve is attached voltage could plummet. Measure the voltage
before and after the valve is attached. Also try the valve at the
controller rather than the lawn; the controller might be defective.

 

[[email protected]]

I've got a real head scratcher.
Long story short: 18 zone, 24-volt AC commercial sprinkler controller
system.
One valve on the system won't operate anymore after running fine for years.
The valve operates when connected to a battery operated testing unit.
Voltage at the controller terminal going out to the zone shows 29 volts.
The wires from the controller at the valve (guessing 200+ foot underground
run, 14 gauge wire) show 27.4 volts.
There's enough current to give you a tickle if you grab the wires.
Connect the 27.4 volts to the valve and nothing happens.

Also dont overlook possibility of a stiff mechanism connected to the
solenoid, or a stiff solenoid due to leakage and corrosion.

A good way to drive solenoids is to use a capacitor to give them an
initial pulse of 2x rated voltage, which very rapidly drops to rated
voltage from the supply.

Really you just need to work it thru, divide and conquer until you know
where the problem is.


NT

 

[G]

Hello Dallas. When you say "The wires from the controller at the valve
(guessing 200+ foot underground run, 14 gauge wire) show 27.4 volts.",
do you mean WITH the solenoid connected? Connected is how you need to
measure that voltage (under actual operating conditions). There is
where you may find that the voltage sags bad, causing or aggravating the
inability of the valve to move.....as a starting point knowing what you
have for test equipment (so far).

Gord

 

[default]

I've got a real head scratcher.



Long story short: 18 zone, 24-volt AC commercial sprinkler controller
system.



One valve on the system won't operate anymore after running fine for years.



The valve operates when connected to a battery operated testing unit.



Voltage at the controller terminal going out to the zone shows 29 volts.



The wires from the controller at the valve (guessing 200+ foot underground
run, 14 gauge wire) show 27.4 volts.



There's enough current to give you a tickle if you grab the wires.



Connect the 27.4 volts to the valve and nothing happens.





My degree was in Business so I start to get fuzzy at this point. Could one
of the wires be missing some insulation somewhere underground and drawing
off enough amperage to keep the solenoid from actuating while still showing
27.4 volts?



Is there anything that could happen to a solenoid coil that could make it
demand more current to operate?



Sadly my $30 meter doesn't have an amperage function. Would hooking the
voltmeter in series with the circuit tell me anything?



Can anyone give me a clue as to what's going on?



Dallas

You want to measure the voltage with the solenoid valve connected to
the power source. They use solid state drivers (triacs) that will
leak enough voltage to appear to be working when they still won't
operate the load if there is no load connected)

If it still doesn't work, switch that channel to another zone and see
if it will work that zone.

One assumes you tested the water supply?

I'd also see what an operating valve uses (what voltage is across it).
Choose a valve the same distance from the controller and measure that
voltage while it is on. 27.5 sounds too high considering nominal is
24 and you should drop some voltage in the line - I know you think it
is connected but that sounds like it isn't. (wire nuts?, corrosion?)

Failing all else, bite the bullet and replace it (or physically switch
it with one of the other's - if that's an option - to see if the
problem stays with the valve).

 

[Dallas]

Thanks to all that replied.

Yes, testing the voltage across the circuit with the solinoid connected
destroyed the voltage (near zero).

We finally found a damaged point in the underground wire where all the
current was leaking off into the ground.

Thumbs up!

Dallas

 

[CRaSH]

Thanks to all that replied.

Yes, testing the voltage across the circuit with the solinoid
connected destroyed the voltage (near zero).

We finally found a damaged point in the underground wire where all the
current was leaking off into the ground.

Thumbs up!

Dallas

Took ya long enough Varmit! d:->))

 

[James Sweet]

It wasn't leaking off into ground, there just wasn't a good path for any
appreciable amount to be drawn by the solenoid.