# Size zone wiring

I need to run zone wires about 800’. Most commercial controllers will require 16ga zone wires for that distance, but that depends on the transformer output in the controller. What is the transformer output voltage in the Rachio G3 and does it’s distance capability compare with other controllers like the RB controllers?

Personally, I think you’d be better off running a heavier guage wire if the valve coils pull enough current to cause a voltage drop at the far end of the cabling. I don’t think I’d want to increase the voltage to the controller, which would in my opinion could damage the controller. I’m not sure that the coils would draw enough current ( I never had reason to measure what my Orbit valves draw, but I might measure it) to cause a voltage drop enough to not operate the valve. Now you got me curious. 800 feet is a long distance and the resistance of 16g wire might be a problem, but I don’t think so.

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OK, so I measured the current that one of my Orbit valves draws that is closest to the controller so wire resistance would not reduce the current over the 20 foot distance of the wiring to that valve: it draws 0.186.3 amps as you can see in the attached photo. The US wiring specs for 16 gauge wire shows that it has a resistance of 4.0 ohms over 1000 feet. 800 feet X2 (common plus zone conductor) = 1600 feet, so the total resistance of the run to one of the zones at that distance 4.0 X 1.6 = 6.4 Ohms. Ohm’s law says E= IR, the Voltage equals the current 0.186.3 times the resistance 6.4 which shows the voltage drop over the 1600 feet would be 1.19 Volts. This all AC volts because the controller supplies AC volts and the Valve coil is designed for 24 Volts AC and is an inductance rather than just a plain resistance. Orbit’s Data sheet shows to use 20 Gauge wire for distances under 800 feet and to use 18 Gauge for distances over 800 feet. 16 Gauge wire is even bigger than 18 gauge, so there should be no problem. I hope this is helpful:grinning:

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Thanks for going to the trouble of your experiment. I have what I need now, except for the 2 miles of zone wires.

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You are welcome.