You would likely be just fine with using any common DC power supply that is between 36 and 48 volts given most general purpose DC motors are not all that fussy about having the exact voltage they are rated for.

I like the simple solution but we don't know what kind of motor is on the valve. It could be a simple brushed motor, or it could (likely, actually) be a servo valve with electronics in it. It would be just fine while the motor is moving and pulling the voltage down to 24V but as soon as it stops, the voltage pops back up to 36/48V and the electronics might not approve.

 

I shouldn't have used the term "trickle charge" because it implies a device, called a trickle charger. What I meant was just a 24V power supply at you base station, and a 24v battery at your remote station. The 24V battery would require very little current to keep topped up.

May be 24V power supply at base station needs some current clipper at level 0.7 A or so for case if battery will suddenly discharged?

 

May be 24V power supply at base station needs some current clipper at level 0.7 A or so for case if battery will suddenly discharged?

The line resistance should provide adequate clipping. Even if the other end is a dead short, the current won't get much over 1 A.

I was tempted to suggest holding the line at a suitable trickle voltage (somewhere around 24 V) and then detect when the voltage goes away as the signal to activate the valve, but that risks having the valve actuate if the lines get cut or the control end loses power, which might not be good. But it would be possible to sense the voltage dropping to some low, but nonzero, range and use that as the signal to actuate the valve.

@sfc3lf Is this motor bidirectional, or is it working against a spring of some kind? In other words, after you turn the valve on, how do you turn it off?

 

I like the simple solution but we don't know what kind of motor is on the valve. It could be a simple brushed motor, or it could (likely, actually) be a servo valve with electronics in it. It would be just fine while the motor is moving and pulling the voltage down to 24V but as soon as it stops, the voltage pops back up to 36/48V and the electronics might not approve.

Do you know the actual working voltage rating of the wire/cable that is in use? Very few multi strand cable set have a rating of less than 300 volts which is more than sufficient to run line voltage on. With that concept you would simply send your line voltage out and back on the two available conductors then add a earth ground stake at the end to make up for the their ground (if needed per your electrical codes) and your done. Just put a .5 - 1 amp fuse on the supply line and its safe.

My home water well pump system is now controlled that way. My house has the pressure tank and switch and it sends a 120 VAC control signal out to a relay at the well that switches the actual 240 VAC well pump on and off. Total run is ~ 700 - 750 feet round trip on 22 - 24 gauge wire in a 9 strand cable that's part of my central boiler remote interface system rated for 300 volt or less.

 

The motor is two-way on-off reversible motor. The trickle charger might not work in this application because the wires will be used to reverse polarity and change the direction of the motor to open and close. The suggestion of AnalogKid to use a higher rated 48vDC power supply with a regulator could solve the issue. That assumes that the higher voltage won't damage the wires. Also, the valve will be underground, so I'll also have to find a weatherproof enclosure for the regulator. Is it possible to get a variable voltage power supply and dial it in on-site to avoid the need of a regulator?

 

That assumes that the higher voltage won't damage the wires. Also, the valve will be underground,

I don't see wire insulation voltage rating being an issue and that critical, especially in this day and age.
Max.

 

The motor is two-way on-off reversible motor. The trickle charger might not work in this application because the wires will be used to reverse polarity and change the direction of the motor to open and close. The suggestion of AnalogKid to use a higher rated 48vDC power supply with a regulator could solve the issue.

How are you going to reverse the polarity?

 

Electric actuated valve uses power-to-open and power-to-close, stays in the last known position with loss of power. On receipt of a continuous voltage signal, the motor runs and via a rugged all metal gear system rotates the ball 90º. The motor is automatically stopped by internal cams striking limit switches. On receipt of a reversing continuous signal, the motor turns in the opposite direction reversing the valve position. Valves with EPS positioner use an analog input signal to control the position of the ball (flow). Electrical connection by prewired cable with flying leads (3 meter/9.8 feet

Sorry I should of put on my glasses

 

I don't see wire insulation voltage rating being an issue and that critical, especially in this day and age.
Max.

Underground low voltage circuit cables have two levels of voltage: 30 V and 150 V.
p. 18 on https://www.ul.com/wp-content/uploads/2014/04/WC_MG.pdf

 

I was tempted to suggest holding the line at a suitable trickle voltage (somewhere around 24 V) and then detect when the voltage goes away as the signal to activate the valve, but that risks having the valve actuate if the lines get cut or the control end loses power, which might not be good. But it would be possible to sense the voltage dropping to some low, but nonzero, range and use that as the signal to actuate the valve.

EDIT: Resistor 33 Ohm need to be 68 Ohm.
Should be exchanged collector and emitter of P-N-P transistor.

 

Ok no electronics in your valves that I can tell. your wires and the limit switches in your motor are both rated 30V. 30V probably won't be quite enough.

If it were me, and if this were something at my house, and if it wasn' something critical (like fire suppression water supply, etc.) I would just put a 40V power supply at the base station and be comfortable that it would "probably" be ok indefinitely. Or at least it would stave off me having to dig the cable up for a comfortable amount of years.

But I can't officially recommend you do that. And if this is for a client or for your work, especially if it's a critical system, if there is any kind of potential liability on your part at all, definately do not do this. This is not "by the book" or legit in any way.

What's the 4-20mA signal for BTW? One of the models of your valve accepts a 4-20mA signal. If your 4-20 is for the valve, then there ARE electronics in it.

 

4-20mA
It kind of leaves a lot out of the datasheet.

EPS positioner use an analog input signal to control the position of the ball (flow).
Don't show that in the DC 24 model

 

The 4-20mA loop is unrelated to the actuated valve. It is connected to a level transducer that is located near the valve. The 2000' cable had a second unused pair, so I've been trying to determine if I can use the same cable to control the valve motor. Thank you to everyone who gave their input and knowledge. I've learned a lot. In particular, Stantor for giving me your thoughts even if it didn't "meet code". As you thought, the project is in-house and not controlling anything that is considered critical. I just want to make sure I don't ruin the cable trying get this to work. I'm comfortable with the margin of error and will proceed with the suggestion.
The project area is located in a lighting prone area. For my other runs, I've been using a surge protection like these. Would the best practice to install a 24-volt surge at the valve and also a 48-volt version at the panel? If this was your install, would you install anything else to protect your investment? Thank you everyone and Cheers to your time you spent helping get this right!

 

Could you run mains AC voltage on one pair of wires and use that to power a 24Vdc, 1A supply (wall-wort) at the far end?
That will significantly reduce the current and voltage drop in the cable.

 

Could you run mains AC voltage on one pair of wires and use that to power a 24Vdc, 1A supply (wall-wort) at the far end?
That will significantly reduce the current and voltage drop in the cable.

His wire is rated for 30 volts. It's a sprinkler system cable

 

His wire is rated for 30 volts. It's a sprinkler system cable

What's it insulated with? Toilet paper soaked in wax?

 

What's it insulated with? Toilet paper soaked in wax?

Well, why not? That's what Chinese capacitors are made of.

 

Well, why not? That's what Chinese capacitors are made of.

I'm just saying that I find some of the rather arbitrary voltage ratings for wire a bit odd at times. I have some wire that is rated for 600 volts that has the same PVC based ,but thinner, insulation jacket than other stuff that has a 150 volt rating.

For me, unless something is obviously special application I typically consider it good for common AC line voltage work. Even more so if it's direct bury rated as I assume the OP's stuff is and if it is and its anyting like the roll of it I have despite it modest voltage rating the insulation is way heavier than most 600 or even 1000 volt rate instrumentation panel wire.

 

I'm just saying that I find some of the rather arbitrary voltage ratings for wire a bit odd at times. I have some wire that is rated for 600 volts that has the same PVC based ,but thinner, insulation jacket than other stuff that has a 150 volt rating.

For me, unless something is obviously special application I typically consider it good for common AC line voltage work. Even more so if it's direct bury rated as I assume the OP's stuff is and if it is and its anyting like the roll of it I have despite it modest voltage rating the insulation is way heavier than most 600 or even 1000 volt rate instrumentation panel wire.

There are properties of various types if wire insulation that make them more or less oil resistant, more or less UV resistant, more or less flexible, more or less abrasion resistant, more or less costly, and finally, better or worse insulators. Just because an insulator is thick doesn't mean it's better for higher voltage (tho usually it does) and a thin insulation doesn't always mean it's a low voltage wire (tho usually it does). The wires in the subsea umbilicals I use at work is rated 4,500V and the insulation is thinner than that of THHN/THWN, MTW, or any of the other typical wires you find. They use a super good insulating polymer, hard to cut, and it' oil resistant and flexible and goes through the most rigorous QA process you've ever heard of (I know because i used to work maintenance in a subsea umbilical plant) . Probably the most expensive wire you can find. On the other end of the spectrum you have this sprinkler system cable that's probably made of recycled phony air Jordan's from the plant across the street in Shenzhen, with pleather, cardboard, and shoelaces mixed into it, and "QA" (note the quotes) carried out by an illiterate trained ape. It's rated 30V for a reason. That's the highest they can guaranteed nothing bad will happen. Sure, you could probably get away with doubling the voltage, maybe even tripling it. But you quadruple it, I don't know. Maybe you're right but if it came down me having to dig up and rebury 2000ft of cable, I would NOT want to find out.

 

The first pair is a 4-20mA loop and I'd like to use the second pair to control the actuated valve motor. The motor draws only .7amps at 24vDC. I've looked at voltage drop calculators and it appears that I could increase the voltage to 42volts to get the proper 24v to the motor. I understand the best solution would be a larger cable, but that isn't practical. I also can't install a wireless system due to visual constraints. Do I risk damage to the cable by having such large voltage losses?

Buy DC-DC Boost Step Up Power Module 3A Volt Converter 3.5V-30v to 5v 6v 9v 12v 24v
for $1 and place it close to valve motor.