Irrigation Wire

I want to know what the limit of distance is recommended and / or size code 18, and how far a heavier gauge wire is needed to operate a standard 24-volt solenoid. I guess 1,000 feet?

If you know a little traction power to the solenoid, then you can calculate the tolerable IR drop in the power cord.

# 18 AWG 6.4ohms down by 1,000 ft (see first link.) The second link below suggests that you need on the solenoid 20V to reliably operate the valve (about 20% of the nominal value. )

So if you measure the coil with the meter you can calculate the resistance of food you can tolerate and still have 20V on the coil.

In other words,

I (coil) = 20V / R (coil) .... is the minimum traction current. It is also the current through the wire.

Knowing this, we can set up a calculation:

I (coil) = I (son)

If

V (coil) / R (coil) = V (son) / R (son)

Rearranging things a bit:

R (son) = V (son) / V (coil) * R (coil).

Tell the coil is 20 ohms (see the third link.) Then the resistance wire is tolerable:

R (thread) = 4 / 20 * 20 = 4 ohms.

That's about 625 feet of wire, total. But remember that you must perform a return loop, so that the entire route is only 313 meters.

Looks like you need to use heavier wire to make the run.

Your proposal is good, it could be from further. I used to build digital circuits and we had to measure the loss to place the repeaters when the loss reaches a certain point, most 24 gauge and 1000 feet of loss is minimal.

hm .. with what you might move 6.385 ohms of resistance wire or say 6.4 ohms, I would go with a heavier wire.