Which factor determines the required conductor size for a valve coil in an irrigation circuit?

• A. Soil type
• B. Controller brand
• C. Number of irrigation zones
• D. Current draw of the valve coil

Answer: (D)

Conductor size is determined by how much current the valve coil draws and the voltage drop that will occur along the wiring run. A valve coil is a fixed 24-volt load, so the amount of current it pulls sets how thick the wire must be to avoid overheating and to deliver enough voltage to the coil at the far end. If the coil draws more current, a larger conductor is needed; and if multiple valves can be energized on the same circuit, you must consider the total current to prevent excessive voltage drop or overheating. The soil type and controller brand don’t change the coil’s electrical draw, and while the number of zones affects total circuit load, the key determinant for the conductor size of a valve coil is the coil’s current draw.