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I have this irrigation caddy unit, and it requires 24VAC.

There's a location outside my house with one ethernet cable and another brown cable with four solid copper wires (black, red, yellow, green). Both of these cables go back to the wiring panel in the closet.

I want to connect the brown cable to the power input on the device and connect the other end to the power supply/brick.

Would there be trouble powering the device?

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What is the amperage or wattage of the device you want to power? –  bib Oct 13 '13 at 1:53

1 Answer 1

up vote 2 down vote accepted

Wire carries current, insulation prevents leakage of voltage.

Any wire can carry any voltage up to the working voltage of the insulation. Category 5 phone cable is rated for 125wV and commonly carries 12-57VDC for Power Over Ethernet, 48VDC for phone and 90VAC for phone ringer operation.

Wire size determines the ampacity (amount of current) the wire can carry. As long as your device pulls 600mA or less, 22 gauge wire should be sufficient. If it needs current in the 2 amp range, you'll need 18 gauge wire. Excessive current heats the wire and can melt the insulation.

Another thing to think about is voltage drop and that is affected by the size of the wire (resistance). You will have a 2V drop in available voltage at the end of a 100ft 22ga cable at 24V/600mA. 1V drop for 50ft at 24V/600mA.

Their specs aren't technical enough to tell you what the current draw is on the device.

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The power supply says 800 mA and 19.2 W... the wire on the power supply is only 24 gauge but it's stranded. –  Jack Oct 13 '13 at 5:06
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You could wire the black and green together to carry one side of the current and wire the red and yellow together to be the other lead. Expanding from Fiasco's numbers from above, the paralleled 22 gauge wires would increase current capacity to 1200mA or somewhat reduce the end to end voltage drop at lower than the 1200mA load. –  Michael Karas Oct 13 '13 at 5:56
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Basically, just as @MichaelKaras says, put one pair on positive, and the other on negative and all's well. I don't know what your length of run is, but normally, bell wire is 20 gauge solid and thermostat wire is 18 gauge stranded. Pairing 22ga wire reduces the voltage drop and allows you to not worry about heating from the current. –  Fiasco Labs Oct 13 '13 at 6:35
    
insulation does not prevent "leakage of voltage," it prevents leakage of current (into whatever the cable is touching). Voltage loss occurs due to the resistance of the wire - thicker wires lose less voltage per foot. –  BlueRaja - Danny Pflughoeft Oct 14 '13 at 4:53
    
@BlueRaja-DannyPflughoeft Technically, yes on leakage, but the ultimate breakdown of insulation is directly related to voltage causing the leakage. And the other was already addressed: Another thing to think about is voltage drop and that is affected by the size of the wire (resistance) –  Fiasco Labs Oct 14 '13 at 15:38

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