LIT-060 Hunter 2004-2005 Product Catalog - Ewing Irrigation

Wire SizingResistance MethodRequired Information• Actual one-way length of wire betweenthe controllers and the power source orthe controllers and valves• Allowable voltage loss along the wirecircuit• Accumulative current flowing throughthe wire section being sized in amperesResistance is calculated using this formula:R = 1000 x AVL2L x IR = Maximum Allowable Resistance ofwire in ohmsper 1000 feetAVL = Allowable voltage lossL = Wire length (one way)I = Inrush currentAVL for controller power wire sizing is calculatedby subtracting the minimum operating voltagerequired by the controller from the minimumavailable voltage at the power source.AVL for valve wire sizing is calculated by subtractingminimum solenoid operating voltagefrom controller output voltage. This number willvary depending on the manufacturer and in somecases with line pressure.Table 1Resistance of Copper WireWire Size Resistance at 20° C (68° F)AWG No. ohms per 1000 feet18 6.3916 4.0214 2.5212 1.5910 1.008 0.636 0.404 0.25Table 2Valve Wire sizing (Maximum One-Way Distance in Feet Between Controller and Valve)GroundControl WireWire 18 16 14 12 10 8 618 850 1040 1210 1350 1460 1540 159016 1040 1340 1650 1920 2150 2330 244014 1210 1650 2150 2630 3080 3450 370012 1350 1920 2630 3390 4170 4880 540010 1460 2150 3080 4170 5400 6670 76908 1540 2330 3450 4880 6670 8700 105306 1590 2440 3700 5400 7690 10530 13330Solenoid: 24VAC, Pressure: 150 PSI, Voltage Drop: 4V,Min. Operating Voltage: 20V, Amperage Peak: .37AValve Wire Sizing Example:Given: The distance from the controller to the valve is 1800 feet. The controller output is 24V. The valve has a minimumoperating voltage of 20V and an inrush current of 370 mA (0.37 Amps).R = 1000 x 42(1800) x 0.37R =40001332R= 3.00 ohms/1000 feetSo, wire resistance can not exceed 3.00 ohms per 1000 feet. Now go to table #1 and select the proper wire size. Since 16gauge wire has more resistance than 3.00 ohms per 1000 feet, choose 14 gauge wire.Table 2 is a quick reference and is set up to provide maximum wire runs given the information at the bottom of the table.128