Nelson Irrigation Corp. 848 Airport Rd. Walla Walla, WA 99362-2271 USA Tel: 509.525.7660 Fax: 509.525.7907 E-mail: [email protected] Web site: www.nelsonirrigation.com
Control Valve
Application
Guide
EXAMPLE FOR SELECTING WIRE SIZE WITH FORMULAS (TWO VALVES):
In the event that there are two valves to turn on per station, the formula procedure is as follows:
Figure 9
STEP 1 and STEP 2 the same as for one valve shown on the preceding page.
STEP 3. Calculate the allowable wire resistance for the valve furthermost from the controller. See the distances shown in
Figure 9 schematic. Use the inrush for two valves of 2 * .278 = 0.556
Rw = 3.6 * 1000 = 1.12 ohms/1000 ft
2900 * 2 * 0.556
STEP 4. The wire resistance must not exceed 1.12 ohms per 1000 feet. Use Table 6. Select the #10 wire size which is only 1.03
ohms per 1000 feet. Be sure to check the controller output specification for two valves and make any needed adjustment to the AVL.
6.3 WHEN YOU NEED TO USE DC POWER
Certain systems may need to be operated without an AC power source. These may be remote systems where generated power
is used, only solar power is available or where DC batteries are used. Option E20, E21, E23, E24 and E30 can be selected
for DC power. The power requirements for the E30 option are shown in Table 4. See Table 4 right hand column for multiplier
factors. The E23 and E24 are two wire and the most common latching solenoids. Latching means that the holding power is
much less than the inrush power required to move the solenoid plunger. Very low holding power is desired to reduce draw
down of the batteries or storage units. Two wire controls are more common and easier to purchase worldwide.
THREE WIRE LATCHING OPERATING PRINCIPLE: Option E20 is a three wire latching solenoid. The solenoid is a bi-stable
plunger type solenoid with two coil windings. The following applies to the E20 solenoid.
A pulse applied to terminals 2 and 3 of the operating coil connects port A (which goes to the AUTO port on the manual
selector) and R (which goes to the upstream). The valve remains in the operated position.
A pulse applied to terminals 1 and 3 of the operating coil connects port A (which goes to the AUTO port on the manual
selector) and P (which goes to the VALVE port on the pressure regulator). The valve remains in the non-operated position.
Simultaneous voltage to both coil windings (1 and 2) must be avoided. Nelson Irrigation Corporation has on going evaluation
of latching solenoids to find the best for your application. Contact the factory for more details on the power requirements
of the E20 option.
SAFETY FIRST!
Always exercise good safety procedures. Persons operating the system, should be warned that personal injury may result from
the high pressure water and potential electrical shock.
Read all warning labels and cautions!
Never remove or modify the valve under pressure.
Be sure water flow through the valve has stopped before doing any work on the system downstream.
Electrical components near water always creates a special danger! Use good electrical safety practices!
Respect local code requirements.
ELECTRICAL APPLICATIONS
16
