DC Voltage Stretch Question

I know that this isn't exactly a PLC question but I figure the people here are the best ones to ask. I have an application where I have a solenoid that sits 3/4 of a mile from any power source, I really do not want to go wireless for one solenoid and wanted to see if I can get someone's opinion on what type of voltage and equipment they would use to get out to the solenoid. My present thoughts are on using DC voltage but I do not know what type of voltage loss I might see, any help here would be greatly appreciated. Once again, I would like to thank everyone who helps out on this website.

Chris

I would go for a current loop.

Kind regards,

According to my opinion you can use DC voltage or AC, to be on the safe side I would use 14AWG with 110V or DC, but to make sure I would increase the the power supply output to 28V.
To feel better I would take 2 rolls of 500 foot 14AWG and cheak if it work and check the voltage drop.Before I install the wires.

Ya know, this isn't an esoteric problem - it is just an application of Ohm's Law. I would assume 24 VDC would be better because of the safety implications of a frayed wire or short to ground in a long wire, but regardless V = I x R. If you know the current or VA requirement of the solenoid (and look at inrush and holding) then you can figure out the voltage drop in the wire to and from the solenoid:

Back to basics - Ohms law says V = I x R. The resistance, in Ohms per thousand feet at 149 degrees F, of various sizes of wire is:

AWG Ohms / 1,000 feet
22 19.0
20 11.9
18 7.51
16 4.73
14 2.97
12 1.87

If you have 1,200 feet of 18 AWG wire for example, 600 feet there and 600 feet back, your extra load is 9 Ohms. The additional voltage drop with a 0.5 Amp current draw is 4.5 Volts. Keep going up in wire size until your power supply voltage minus the drop is within the limits of the solenoid.

Distance Control

There are two problems associated with using AC for long distance control.

First there is the voltage drop problem mentioned by Tom Jenkins. The actual engineering term is series impedance and it can involve more than just the wire resistance.

Second there is a problem with shunt capacitance. It is conceivable that the capacitance between the line and load conductors (especially if in a water filled conduit) will be large enough to maintain voltage at the field device.

Here is a simple reference source (although it is from a specific manufacturer):
http://ecatalog.squared.com/pubs/Ma...s/Relays, Industrial Control/8501X/M-379F.pdf

Thanks for everyone's reply, I will use a 24vdc power supply using #12 guage wire. Thanks again.

Chris