Nelson 800 Series User guide

800AG-4
800 SERIES CONTROL VALVES
CONTROL VALVE APPLICATION GUIDE
By Tom Young, P.E., M.S.

Nelson Irrigation Corp. 848 Airport Rd. Walla Walla, WA 99362-2271 U A Tel: [phone] Fax: [phone] E-mail: [e-mail] Web site: www.nelsonirrigation.com
Control Valve
Application
Guide
1.0 TYPES OF CONTROLS ON 800 SERIES VALVES
NELSON 800 Series Control Valves are available in several configurations. Understanding these basic valves puts a
designer in a better position to understand all of the combined types, functions and design requirements. Valves are best
categorized by operating control function.
These are the operating control functions presently available:
 Simple ON/OFF Control (manual or automatic) Valves
 Pressure Control Valves (these valves work using a pressure control regulator)
Pressure Reducing
Pressure Sustaining
Pressure Relief
 Rate-O -Flow Control Valves (used to maintain a desired flow rate)
 Combination Valves
More than one control function. EXAMPLE: pressure reducing with automatic on/off.
 Special Purpose
Check Valves
Sleeve Exhaust
Special on/off mode or special function.
2.0 SELECTING THE RIGHT VALVE
Selecting the right valve for the job consists of understanding, then selecting the proper control function and proper valve
sizing. The best sequence is 1) Choose the control function to serve the purpose, 2) Select the valve size and pressure rating,
and 3) Verify that the operating range for the selected valve is correct. This document is to be used as a guideline and is
not a complete strategy for design.
2.1 UNDERSTANDING THE CONTROL FUNCTIONS
2.1.1 SIMPLE ON/OFF
MANUAL CONTROL: The MANUAL ON/OFF control is used to open or close the valve. The flow through the valve is controlled
by a rubber sleeve which is actuated by hydraulic pressure. The valve is either in the fully opened or the closed (shut off) position.
The AUTO position on the selector has no effect on valve control but is used when the valve is equipped with automatic controls.
AUTOMATIC CONTROL: If the valve is equipped with an electric solenoid, the on/off function can be automatic by using
an electric controller. When the selector is pointed to the AUTO position then the electric solenoid is used to automatically
open or close the valve. The 3-way electric solenoid must be energized to open the valve and de-energized to close the
valve. Pointing the manual selector handle to OPEN or CLOSE will override the AUTO control.
2.1.2 PRESSURE CONTROL VALVES
Pressure control valves react or respond through a pressure control regulator. The pressure control regulator directs water
flow which positions the sleeve during operation. If the control function is pressure reducing, the sleeve position (or flow
through the valve) is controlled by downstream pressure. If the control function is pressure sustaining or relief, the sleeve
position is controlled by upstream pressure.
2.1.3 RATE-OF-FLOW CONTROL VALVES
The Rate-Of-Flow control valves operate by a flow sensing probe in the pipe. A calibrated adjustment screw is used to set
the desired flow. The flow velocity moves the probe to maintain the desired rate-of-flow.
2.1.4 COMBINATION VALVES
Combining functions of more than one control is possible with the NELSON 8 Series Control Valve. The most common
combination is the automatic on/off combined with a reactive pressure control.
2.1.5 SPECIAL PURPOSE VALVES
The check valve feature is used to prevent flow reversal. The check option is available separately or with most on/off and
reactive control functions.
TYPES OF CONTROLS
2

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The sleeve exhaust is a special valve used to exhaust water from the sleeve chamber and allow fast opening response on the
valve. The sleeve exhaust is most often used with turbine well pumps. During start-up a column of water begins moving at high
velocity. When the water contacts the valve, quick opening is required to prevent damage.
Special on/off mode valves are used where standard valves don't work due to system requirements. An example
of this is the hydraulic remote control which eliminates the need for wires in the field. See section 2.4.2 for more information
on the hydraulic remote function. Contact the factory for specific details on the special function valve control. See Appendix
D for a quick lookup table.
2.2 TYPICAL VALVE APPLICATIONS
Typical valve applications in agriculture are shown in Figure 2 on the following page labeled TYPICAL CONTROL APPLICATION.
The sketch indicates where the different valves could be applied. Not every valve control type is required on most systems.
The sketch is for demonstration purposes only.
2.3 800 SERIES SLEEVE VALVE PARTS TERMINOLOGY
It is necessary to know the name of the parts of the basic sleeve valve to understand how the valve functions. The cross section
drawing (Figure 1) shows the general parts of the Nelson 8 series valve.
SELECTING THE RIGHT VALVE
Figure 1
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Control Valve
Application
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Figure 2
TYPICAL CONTROL APPLICATIONS
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Control Valve
Application
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2.4.2 DESCRIPTION OF FUNCTIONS LISTED IN THE SELECTION GUIDE
MANUAL ON-OFF
VALVE CONTROL FUNCTION (items D1, E1 on the VALVE SELECTION GUIDE):
The MANUAL ON-OFF model of the 8 Series Control Valve is a hydraulically operated sleeve type valve with a manual
control. The MANUAL ON-OFF control is used to open or close the valve. The valve is normally either in the fully opened
or the closed (shut off) position but pointing the selector handle mid- way between ports can hold the sleeve in a partly open
position. The "AUTO" position on the selector has no effect on valve control but is used when the valve is equipped with
automatic controls.
ELECTRIC ON-OFF
VALVE CONTROL FUNCTION (items D1, E2 through E72 on the VALVE SELECTION GUIDE):
The ELECTRIC ON-OFF model of the 8 Series Control Valve is a hydraulically operated sleeve type valve with an electric
solenoid control. The valve is either in the fully opened or the closed (shut off) position. When the selector is pointed to the
"AUTO" position then the electric solenoid is used to automatically open or close the valve. The 3-way electric solenoid must
be energized to open the valve and de-energized to close the valve. Pointing the manual selector handle to "OPEN" or
"CLOSE" will override the "AUTO" control except when the selector is pointed to "OPEN" the pressure reducing control still
functions but the solenoid has no effect.
PRESSURE REDUCING MANUAL ON-OFF
VALVE CONTROL FUNCTION (items D2 through D4, E1 on the VALVE SELECTION GUIDE):
The PRESSURE REDUCING MANUAL ON-OFF model of the 8 Series Control Valve is a hydraulically operated sleeve
type valve with a pressure reducing pressure control kit and a manual on-off. When the selector is pointed to the "AUTO"
position then the valve will automatically reduce a higher inlet pressure to a constant lower downstream pressure. The
pressure reducing control is adjustable to give a constant down stream pressure even with fluctuating upstream pressure.
The manual selector is used to manually open or close the valve. Pointing the manual selector handle to "OPEN" or "CLOSE"
will override the "AUTO" control except, when the selector is pointed to "OPEN" ,a safety plug installed at the factory must
first be removed to open the valve.
PRESSURE REDUCING ELECTRIC ON-OFF
VALVE CONTROL FUNCTION (items D2 through D4, E2 through E72, on the VALVE SELECTION GUIDE):
The PRESSURE REDUCING ELECTRIC ON-OFF model of the 8 Series Control Valve is a hydraulically operated sleeve
type valve with a pressure reducing pressure control kit and an electric solenoid. When the selector is pointed to the "AUTO"
position then the valve will automatically reduce a higher inlet pressure to a constant lower downstream pressure. The
pressure reducing control is adjustable to give a constant downstream pressure even with fluctuating upstream pressure. The
electric solenoid is used to automatically open or close the valve remotely. When in the "AUTO" position the 3-way electric
solenoid must be energized for the pressure control to work and de-energized to close the valve. Pointing the manual selector
handle to "OPEN" or "CLOSE" will override the "AUTO" control except, when the selector is pointed to "OPEN" , the pressure
reducing control still functions but the solenoid has no effect.
PRESSURE SUSTAINING/RELIEF
VALVE CONTROL FUNCTION (items D5,D8,D9, with E1 on the VALVE SELECTION GUIDE):
The PRESSURE SUSTAINING/RELIEF model of the 8 Series Control Valve is a hydraulically operated sleeve type valve
with a pressure sustaining/relief pressure control kit and a manual on-off. When the selector is pointed to the "AUTO" position,
then the pressure control kit will automatically sustain the upstream pressure on the valve. If the valve is installed in-line o
the main low ,it will maintain the desired upstream pressure by controlling the amount of water that is allowed to flow through
the valve. If the valve is installed on a tee or bypass which allows ree discharge, then it will maintain the desired upstream
pressure by relieving flow through the discharge tee. The pressure sustaining/relief control is adjustable to sustain or relieve
at a desired upstream pressure. The manual selector is used to manually open or close the valve. Pointing the manual selector
handle to "OPEN" or "CLOSE" will override the "AUTO" control, a safety plug installed at the factory must first be removed to
open the valve. Several variations of this control are available to accomplish the desired result. See Appendix D for a quick
lookup table of options.
RATE-OF-FLOW CONTROL
Valve Control Function (items D18 on the VALVE SELECTION GUIDE):
The RATE-OF-FLOW CONTROL model of the 8 Series Control Valve is an add on control that maintains a preset flow
rate by means of a velocity sensing probe in the pipe. An adjustment screw is used to set the desired flow rate. This control
can be combined with most other controls.
SELECTING THE RIGHT VALVE
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Control Valve
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SPECIAL ON/OFF MODES
Special on/off modes are available on many of the control functions. For a list of the available modes contact the Nelson factory.
Note in Figure 3 the option E8 . The hydraulic remote is operated via hydraulic tubing which is run from the controller to the
valve instead of electric wire. The electric solenoid is located near the controller. Wires in the field are minimized. This is u s e d
in areas which have a high potential for lightning damage to the electric system. A special function S1 can also be used to
accomplish the same purpose if infield elevation is minimal (See Appendix D).
2.4.3 PRESSURE CONTROL ACCURACY (SENSITIVITY BUSHING)
The accuracy of the regulating control is a combination of valve friction loss, the slight hysteresis within the regulator and the
sensitivity bushing used in the pressure control. The valve friction loss is dependent upon flow rate. It can be determined from
the loss plot in Graph 1. The overall accuracy of regulation is shown in Table 1 below.
CONTROL RANGE ACCURACY OF SENSITIVITY BUSHING OPTION SELECTED
SELECTED RED BLUE BLACK
5-50PSI (.3-3.4Bar) ±1PSI (.07Bar) ±1.5PSI (.1Bar) ±2PSI (.13Bar)
10-120PSI (.7-8.3Bar) ±3PSI (.21Bar) ±4.5PSI (.31Bar) ±6PSI (.41Bar)
10-200 PSI (.7-13.8Bar) ±4PSI (.28Bar) ±7PSI (.48Bar) ±9PSI (.62Bar)
For more detail on the sensitivity bushing feature see Section 4.3 and Appendix A.
INSTALLATION HINT: To improve regulator accuracy, avoid installing a pressure tap in a turbulent flow area.
An impeller type flow meter immediately upstream may create turbulence that can cause reduced pressure
control accuracy. For pressure reducing control, a down stream pressure tap at the end of a 24 inch (6 cm)
long straight pipe will help. Also, use of a straight pipe on the upstream end of the valve will help. To be effective
the upstream pipe should be a minimum five pipe diameters long.
3.0 PROPER VALVE SIZING
Proper valve sizing is critical in designing control valve systems. The valves must be sized correctly for the reactive control
functions to work (reducing or sustaining). A high percentage of control valve problems can be directly traced to the initial
selection of the wrong size valve. Be aware of these two common problems:
POTENTIAL PROBLEM #1: The most common error occurs in over-sizing a pressure control valve. The error occurs by
ignoring the operation and specifying that the size be the same diameter as the pipe. While this simplifies installation,
it may result in the use of a valve that is too large. At lower flow rates this over sizing leads to severe problems such
as cavitation, water hammer and pressure cycling.
POTENTIAL PROBLEM #2: Almost as common as the above is selecting the control valve from flow graphs. Such graphs
set the limits of minimum and maximum flow rates for each size but the graphs do not account for the pressure drop
across the valve. Since both factors, flow rate and pressure drop, combine to determine the sleeve position both must
be taken into account for the proper sizing of reactive control valves.
Information in the application guide is to aid in avoiding the common problems.
3.1 SIZING SIMPLE ON/OFF VALVES
To size simple on/off valves a designer must look at the valve pressure
rating and then the friction loss. Doing this will assure a valve with
adequate pressure rating is used and also that pressure loss through
the valve will be allowed for in the design.
3.1.1 PRESSURE REQUIRED TO OPEN THE VALVES
The minimum necessary pressure to open the valves is shown in
Table 2, to the right.
Table
1
PROPER VALVE SIZING
Table 2
VALVE RATING
50 PSI  C1 MODEL begi ope i g = 2 PSI
fully ope = 10 PSI
200 PSI  C2 MODEL begi ope i g = 6 PSI
fully ope = 28 PSI
80 PSI  C3 MODEL begi ope i g = 6 PSI
fully ope = 18 PSI
7

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Control Valve
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Graph 1
PROPER VALVE SIZING
3.1.2 VALVE PRESSURE LOSS
The reason to consider pressure loss through the valve is to assure adequate pressure will be available to the irrigation system.
Pressure loss is defined by the following basic equation:
DP = (Q/Cv)2
P1= Pressure on the upstream side of the valve
P2= Pressure on the downstream side of the valve
DP = Pressure loss across the valve in PSI
Q = Flow through the valve in GPM
Cv= Valve sizing coefficient (flow rate at which one psi DP occurs.)
NOTE: Cv provides an index for comparing the capacities of different size valves. The Cv coefficient is defined as the flow
(GPM) which will pass through the valve with a pressure loss of 1 PSI (the larger the coefficient the greater the valve capacity).
The Cv for the Nelson 8 Series control valve is:
8" size Cv = 2 GPM
6" size Cv = 11 GPM
4" size Cv = 31 GPM
3" size Cv = 24 GPM
2" size Cv = 115 GPM
The following graph can be used to determine pressure loss for a simple ON/OFF valve. GRAPH 1 applies to a fully open
valve. The valves were tested with adequate pressure to be fully open as listed in Table 2. Pressure control valves typically
operate in a partially closed condition. See the section 3.2 on sizing other reducing and sustaining valves for more information.
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3.2 SIZING PRESSURE CONTROL VALVES
To size pressure control valves, both the pressure loss and the operating conditions must be considered. Generally the
pressure control valve is only partially open. The sleeve reacts to the pressure regulator which responds to the changes in
the irrigation system pressure. To correctly size the 8 Series valve size, three things must be considered: 1) the pressure
differential, 2) the flow through the valve and 3) the expected downstream pressure.
When doing a design, determine the worst case pressure differential operation point. A large pressure differential and a
low flow condition will position the sleeve very near the center seat. This condition should be avoided. It is generally best
to select the smallest valve which will work.
If cavitation occurs it could cause wear and deterioration of the valve parts. Nelson Irrigation can make no guarantee that
the valve will work under all conditions because of the many variables which can be encountered. Ongoing tests are being
conducted at this time to exactly identify the areas of operation that are safe. Each valve style has unique performance.
Contact the Nelson Irrigation factory for the latest test results and information on the valves.
A NOTE OF CAUTION: Significant fluctuation of pressure can be a problem in some hydraulic systems if a cyclic pressure
wave develops. Abrupt pressure change or flow change is a potential cause which could upset the valve. It is also possible
that extra long pipe, either upstream or downstream, or valves in series can create a condition where the regulator "hunts"
and is not stable. This condition is difficult to predict. Many times the problem can be avoided by using a
RATE-OF-FLOW control slowly
filling the line or slowly changing flow rate. If the unstable situation is due to pressure control responsiveness, then see Section
4.3 or contact the Nelson factory for assistance regarding the pressure control sensitivity options available which have been
designed to solve such problems. Impeller type flowmeters cause turbulence that can affect the valve sleeve. Do not locate
flowmeter immediately upstream of the valve. If a flowmeter is to be used then it is best to locate it downstream of the valve.
4.0 UNDERSTANDING HOW THE PRESSURE CONTROL REGULATOR WORKS
The regulator used on the NELSON 8 Series Control Valve is a three-way (3-way) regulator. The regulator adjustment screw
is used to establish the pressure set point. If the pressure is higher than the internal spring then water is directed through the
regulator to change the sleeve position.
Other two-way (2-way) regulators function differently from the Nelson 3-way regulator. See the discussion on differences in
section 4.1. The following page (Section 4.2) shows in Figure 4 how the Nelson 3-way control regulator functions and the
resulting affect on the 8 Series valve under different situations.
4.1 DIFFERENCES BETWEEN 3-WAY AND 2-WAY REGULATORS
The 8 Series pressure control is a 3-way, spool-type pilot designed to serve pressure regulating purposes. The pressure
control is a self contained regulator with no external accessories needed. It works very well for both pressure reducing and
pressure sustaining or relief. While many other manufacturers use 2-way pressure control pilots that depend upon continuous
water flow through them, the 3-way pilot on the NELSON 8 Series Control Valve operates by directing very small amounts
of water in and out of the sleeve chamber.
The 3-way pilot on the NELSON 8 Series Control Valve has the following benefits:
 LOWER PRESSURE LOSS: The 3-way pilot reduces pressure loss across the valve because when turned to open; the valve
completely opens.
 LESS FILTRATION: Water moves through the controls only when there is a change in line pressure. At steady pressure
conditions, there is no water flow through the control pilot.
 SIMPLE ADJUSTMENT: Setting of the desired pressure is simple with the Nelson 3-way regulator. Only a single adjusting
screw is used and no flow control auxiliary devices are required. See Appendix A for pressure adjustment control instructions.
Due to the features of the 3-way pilot, maintenance of the NELSON 8 series pressure control pilot is minimum and many
times troubleshooting of the controls is simple and can be done with little training.
 MORE ACCURATE: The 3-way pilot on the NELSON 8 Series Control Valve has a pressure control regulator which is
extremely reliable and sensitive to slight pressure changes.
 LESS COMPLICATED: The Nelson 3-way pilot eliminates the need for flow regulating needle valves reducing maintenance
requirements. The 3-way regulator filter may never need cleaning because of the low quantity of water flow required for
the control pilot. This helps in the reliability of the entire control package!
HOW PRESSURE CONTROL WORKS
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4.2 HOW THE VALVE RESPONDS TO THE CONTROLS  Figure 4
Solenoid energized
The upstrea water is blocked.
The sleeve cha ber is vented to
the at osphere, the flow of the
valve is open.
Solenoid de-energized
The upstrea water is applied to
the sleeve cha ber. The flow is
closed off by the sleeve against
the center seat.
SOLENOID
CONTROL
HOW PRESSURE CONTROL WORKS
10
PRESSURE
REDUCING
CONTROL
Pressure lower than
control set point
The pressure regulating control is te porarily
out of balance. The sleeve cha ber pressure
is opened to vent to the at osphere.
Pressure same as
control set point
The pressure control is in balance.
Pressure higher than
control set point
The pressure regulating control is te porarily
out of balance. The sleeve cha ber pressure
is opened to upstrea pressure until the set
point is reached.

Control Valve
Application
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4.3 PRESSURE CONTROL SENSITIVITY AND ADJUSTMENT
The Nelson 8 Series pressure
control is designed with a sensitivity
response bushing which can be easily
changed to give the valve different
sensitivity. A change in sensitivity is
useful in solving pressure cycling
problems. The drawing in Figure 5
shows the location and options of
these bushings. A convenient
calibrated scale is provided on the
adjustment stem. The scale is useful
for approx-imate pressure setting. It
is always recommended that an
accurate pressure gauge be used on the valve to set the exact pressure needed. The RED bushing can be used for very accurate
pressure control on drip systems. See Section 2.4.3 and also Appendix A for details on the Nelson pressure control accuracy.
4.4 FILTRATION OF THE CONTROL CIRCUIT WATER
Filtering the water for the pressure control, solenoid and other control components is
needed for reliable operation. The internal filter provides some self cleaning and the
external filter has the advantage of being cleaned while the system is operating. See
Appendix B for a comparison and discussion of the internal and external filter options.
See Table 3 for the water volume required to fully open or close valve.
CAUTION! Water sources containing excessive debris should have some filtration.
Figure 5
(Nelson Pressure Control)
HOW PRESSURE CONTROL WORKS
11
PRESSURE
SUSTAINING/RELIEF
CONTROL
Pressure lower
than control set point
The pressure sustaining control is te porarily
out of balance. The sleeve cha ber pressure
is opened to upstrea pressure until the set
point is reached.
Pressure same as
control set point
The pressure control is in balance.
Pressure higher
than control set point
The pressure sustaining control is te porarily
out of balance. The sleeve cha ber pressure
is opened to vent to the at osphere valve
opens ore.
WATER VOLUME REQUIRED TO
FULLY OPEN OR CLOSE VALVE
8" 4 quarts
6" 2 quarts
4" 1 pi t
3" 1 cup
2" 5 oz. (145ml)
Table 3

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Control Valve
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Large pieces of trash and debris (1/2 inch or bigger) can get caught in the upstream side of the valve cage. The result is
partial blockage and extra pressure loss through the valve. If this condition happens then the material can be easily removed
by taking the valve out of the line and cleaning out the debris.
4.5 VALVES USED IN LOW TEMPERATURE
If the valve is to be used during low temperature (frost control for example) then the controls need to be covered. The
surrounding temperature must be high enough to keep ice from freezing in the control tube. Remember there is very little
water flow in the 8 Series controls. The result of ice forming in the control tube is that the valve can not operate correctly.
See Appendix B for information on draining external filters.
5.0 ATTENTION TO THE DANGER OF WATER HAMMER AND SURGE
5.1 WATER HAMMER REDUCED BY SMOOTH OPERATION OF THE 800 SERIES
Water hammer is the shock caused by suddenly arresting the flow of water in a pipe. This could happen by rapidly filling a
long pipe or in the case of pump shut down where water begins moving back toward a pump before a check valve can close.
The most likely time for water hammer to occur is the period of time during start-up and shut down of a system. The valve
ON/OFF speed has a great affect on water hammer. Entrapped air rapidly moving within a system can also be a cause of
water hammer. The rapid start up of a pump can cause water hammer in the case where no valve is used.
Severe water hammer can cause damage to pipes, pump, pressure
regulators and seals. The water hammer shock waves move at the
speed of sound in water (466 ft./sec.). The time to control the wave
is during the design. General rules of thumb are: (1) control the
start-up so that in filling a long pipe system, no more than 1½ times
operating capacity (flow) is used; The Nelson RATE-OF-FLOW can be
used to automatically fill the pipe at a rate 1 %-15% above
operating flow. (2) limit flow velocity in the pipe to 6 ft./sec. or lower.
(3) Select the Nelson 8 Series valve that has been designed for
smooth operation on opening and closing (See Figure 6 showing
closing speed of Nelson compared with other brands).
5.2 USE AIR VENTS TO PREVENT AIR ACCUMULATION
The sudden release of air in a system can cause pipe failure. Air control valves are necessary to allow air to escape and to
prevent a vacuum pressure which can collapse plastic pipe. The Nelson ACV2 air control valve should be at high points
in the piping, at extreme increases in pipe grade, downstream of valves which could possibly slam shut, and downstream of
pipe where the flow could trap air. The ACV2 is a combination air relief and air release valve design to solve both air
entrapment and vacuum problems.
5.3 SOME THINGS WHICH CAN HELP REDUCE THE DANGER OF WATER HAMMER
Select a slow opening/closing control on the valve or manually throttle the valve during opening.
Use a two stage opening electric timer to fill the system. See SPECIAL ON/OFF modes (section 2.4.2)
Use check valves to keep water in the bulk of the pipe system in order to minimize filling time.
Use combination air controls which both release air and act as a vacuum breaker. Place vents at all needed locations.
Figure 7
WATER HAMMER AND SURGE
Figure 6
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5.4 PRESSURE CYCLE INDUCED BY THE ELASTICITY OF HOSE AND TUBING
Micro-irrigation zone pressure control valves can experience pressure cycling due to the elastic nature of the tubing. In the
event a large zone of micro/drip tubing is empty, the valve will fill the tube using full flow. When the tubes are full the pressure
expands the tubes much like a balloon. The valve will respond late to over pressure situation. Due to the elasticity of the tube
the valve may even shut-off until the pressure in the tube drops below the set point at which time the cycle again starts.
The problem is best handled by slow filling of the zone. (Many times slow filling is not an option because of the need to
have frequent irrigation.)
Use a design which keeps the zones small to help reduce the problem.
An excellent way to optimize the filling time and reduce the pressure cycle potential is by use of a RATE-OF-FLOW control option.
.0 ELECTRICAL APPLICATIONS
Valves can be equipped with optional electric solenoids for remote operation. Controllers and electric remote control valves
must be properly wired together, otherwise operation of the system will be affected and become unreliable. Controllers
are furnished standard with a nominal input voltage rating of 115 volts AC, 6 Hz (Hertz or cycles) and an output of 24
volts AC on the secondary side for powering electric valve solenoids. There are many optional input voltages in both 5
and 6 Hz. Most solenoids will work with both 5 and 6 Hz. Start by understanding the needs for the controller. Some
controllers will only operate one valve per station. Select a controller which not only has the number of zones required but
also can operate the number of valves required per station.
The current draw will vary with make and model, depending on the amount of current required to operate the controller itself
and the number of valves that the controller is designed to operate per station. A qualified licensed electrician should be
employed to install and connect the controller to an adequate power source in compliance with local codes. For the average
system, wire size for the controller power supply is governed by local codes. The proper wire size must be calculated for the
controllers at remote distances from the power source. This application guide will not address the controller input wire size
requirement but will restrict the discussion for sizing of wire to the wire size required from the controller to the valve solenoids.
6.1 VALVE WIRING (FROM THE CONTROLLER TO THE VALVE)
The most common NELSON 8 Series
solenoid used on a zone control valve is the
24 VAC (part #751 - 15). Two wires are
required to provide the secondary low
voltage power supply for these valve
solenoids. The common wire serves all
solenoids. A power or hot wire from
the controller to each solenoid completes
the circuit. A typical wiring schematic for
one valve operating is shown in Figure 8.
6.2 METHODS OF WIRE SIZING
The following gives two methods of wire sizing which will result in minimum wire size and therefore selection of the wire size
of least cost. Tables can be used to select wire size for simple systems. When the wire run distances exceed those given in the
tables or for more complicated systems, the wire sizing must be calculated using formulas. Formula usage will be explained later.
6.2.1 WIRE SIZING WITH TABLES
Table 4 has been prepared for the Nelson 24 VAC solenoid (part #751 - 15). This table makes selection of wire size simple.
The calculations for Table 4 are made to assure that adequate voltage (2 .4 VAC) and inrush current (~ .3 amps) will be
available to the solenoid. Note other assumptions listed at the bottom of the table.
EXAMPLE: Find the maximum length of run for a system with 15 PSI maximum line pressure using 12 AWG size wire.
SOLUTION: Enter the 15 PSI chart of Table 3, follow the 12 AWG row to the 12 AWG column and read the answer
for maximum length of run of 3497 feet.
ELECTRICAL APPLICATIONS
13
Figure 8

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Control Valve
Application
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Table 4  GUIDE FOR MAXIMUM LENGTH OF WIRE RUN
NELSON 8 SERIES SOLENOID
Option E4 and E41(one valve operating)
MAXIMUM LENGTH (FEET) OF RUN (distance from controller to valve) FOR VARIOUS WIRE SIZES (for 24VAC solenoid
-- OPTION E4 Inrush .3A)
Common Power Wire *AWG
Wire AWG 1 16 14 12 10 6
1 1093 1342 1566 1751 1893 1993 2059
16 1342 1736 2132 2490 2786 3009 3163
14 1566 2132 2760 3392 3966 4434 4775
12 1751 2490 3392 4399 5416 6328 7047
10 1893 2786 3966 5416 7047 8672 10081
1993 3009 4434 6328 8672 11270 13772
62059 3163 4775 7047 10081 13772 17703
Common Power Wire *AWG
Wire AWG 1 16 14 12 10 6
1 869 1066 1245 1392 1504 1584 1637
16 1066 1380 1694 1979 2215 2392 2514
14 1245 1694 2194 2696 3153 3524 3796
12 1392 1979 2696 3497 4305 5030 5601
10 1504 2215 3153 4305 5601 6893 8013
1584 2392 3524 5030 6893 8958 10947
61637 2514 3796 5601 8013 10947 14071
MAXIMUM LENGTH (FEET) OF RUN (distance from controller to valve) FOR VARIOUS WIRE SIZES (for 24VAC solenoid
-- OPTION E41 Inrush 1.1A)
Common Power Wire *AWG
Wire AWG 1 16 14 12 10 6
1 246 302 353 395 427 449 464
16 302 391 481 561 628 678 713
14 353 481 622 765 894 1000 1077
12 395 561 765 992 1221 1427 1589
10 427 628 894 1221 1589 1955 2273
449 678 1000 1427 1955 2541 3105
6464 713 1077 1589 2273 3105 3991
ASSUMPTIONS MADE IN CALCULATIONS: Co troller mi imum output 24VAC. The allowable mi imum voltage required at the
sole oid is 20.4 VAC. The table gives the maximum dista ce i feet from the co troller to the valve eve though calculatio s for
this table i clude total wire le gth from the co troller to the valve a d retur . Commo a d power wire are assumed to be the same
le gth a d o e sole oid operati g. Specific wire resista ce is for solid copper wire at 85 deg. F. (29 deg. C). This table is based
upo i rush curre t required for Nelso #7510-015 sole oid.
EXAMPLE OF USING TABLE 4: E ter the table for 50 PSI maximum li e pressure. Fi d the maximum le gth of wire ru (dista ce
from co troller to valve) usi g 14 AWG power wire a d 16 AWG commo wire is 2132 feet.
150 PSI
maximum
li e pressure
* AWG =American
Wire Gage size
50 PSI
maximum
li e pressure
LOW POWER
SOLENOID
ELECTRICAL APPLICATIONS
HIGH POWER
SOLENOID
150 PSI
maximum
li e pressure
14

Control Valve
Application
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Nelson Irrigation Corp. 848 Airport Rd. Walla Walla, WA 99362-2271 U A Tel: [phone] Fax: [phone] E-mail: [e-mail] Web site: www.nelsonirrigation.com
In the event that the controller has a higher voltage output than 24 VAC, longer wire runs can be made. See Table 5 for the multiplier
which can be used in conjunction with Table 4 to give the maximum length of run for controllers with higher voltage output.
EXAMPLE: If the controller voltage output is 27 VAC, the lengths in Table 4 can all be increased by
a multiplier factor of 1.8.
In the event that there are two valves which must turn on per station; and they are both at approximately the same location,
a multiplier factor of .46 applied to lengths shown in Table 4 will find the maximum length of run for the wires. The controller
current output must be at least 1 amp for both valves per station to work.
Multiplier Factors for Various Controller output Voltages and Optional Solenoids:
6.2.2 WIRE SIZING WITH FORMULAS
When the wire run distances exceed those given in the tables or for more complicated systems, the wire sizing must be
calculated using formulas.
Data needed to size wire is:
(1) the maximum current draw of the valve in amps (Iinrush).
(2) distance in feet (one way) to the valve from the controller (L).
(3) maximum expected line pressure on the valve solenoid.
(4) the allowable voltage loss (AVL) in the wire without affecting function of the solenoid .
(5) controller output voltage (obtained from manufacturer)
The formula for resistance is:
Rw = AVL * 1000 E . 1
L * 2 * Iinrush
in which Rw is resistance of the wire (ohms). The "2" in the formula is used to double the length to include the common and
power wire of equal length.
EXAMPLE FOR SELECTING WIRE SIZE WITH FORMULAS (ONE VALVE):
STEP 1. Find AVL by subtracting the valve operating voltage (2 .4 VAC) from the controller output voltage.
24 VAC - 2 .4 VAC = 3.6 VAC.
STEP 2. Determine the inrush current from Table 6. At 1 PSI line pressure it is .278 amps.
STEP 3. As an example for 3 feet wire run calculate Rw = (3.6 * 1 ) = 2.16
3 * 2 * .278
STEP 4. The wire resistance must not exceed 2.16 ohms per 1 feet. Select the proper wire size from Table 7.
Since #14 has resistance of 2.63 and this exceeds the 2.16 ohms allowable, select the #12 wire size which is only 1.65.
ELECTRICAL APPLICATIONS
Table 5 Table 6 Table 7
Controller
Output
Voltage
28
27
26
25
24
23
22
24VAC
(low
power)
2.1
1.8
1.5
1.28
1.
.7
.44
24VDC
2.1
1.8
1.5
1.28
1.
.7
.44
Maximum
Line Pressure
5 PSI
1 PSI
15 PSI
24V AC & DC
Iinrush
current
.248 amps
.278 amps
.312 amps
Wire
Size
AWG
18
16
14
12
1
8
6
Specific
Resistance*
Ohms/1 ft
6.64
4.18
2.63
1.65
1. 3
.64
.41 *85° F
15

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Control Valve
Application
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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 = .556
Rw = 3.6 * 1 = 1.12 ohms/1 ft
29 * 2 * .556
STEP 4. The wire resistance must not exceed 1.12 ohms per 1 feet. Use Table 6. Select the #1 wire size which is only 1. 3
ohms per 1 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 E2 , E21, E23, E24 and E3 can be selected
for DC power. The power requirements for the E3 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 E2 is a three wire latching solenoid. The solenoid is a bi-stable
plunger type solenoid with two coil windings. The following applies to the E2 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 E2 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

Control Valve
Application
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Nelson Irrigation Corp. 848 Airport Rd. Walla Walla, WA 99362-2271 U A Tel: [phone] Fax: [phone] E-mail: [e-mail] Web site: www.nelsonirrigation.com
PRESSURE CONTROL REPLACEABLE SENSITIVITY BUSHING
This sensitivity bushing is designed to be easily replaced and is used to change the pressure control response
in order to solve pressure cycling problems or to make the valve more accurately control pressure.
APPENDIX A
17
E AMPLE 1: A drip irrigation system requiring 10 PSI: the upstream pressure does not change
dramatically with changes in flow rate. The valve is close to the drip tape. Choose the 5-50 PSI
pressure control because it will maintain 10 PSI more accurately than the higher pressure controls.
Choose the red sensitivity insert to further increase the accuracy of downstream pressure.
E AMPLE 2: A deep well turbine feeding some wheel lines and a pivot: the upstream pressure varies
significantly with changing flow rate and long mainlines are used. Choose the 25-200 PSI pressure
control because it will not try and make small changes to this very dynamic system. Use the black
sensitivity insert to further dampen the pressure controls response. This system is like a long freight
train ... it is not always constructive to micro manage the pressure.

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Control Valve
Application
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FILTER SELECTION FOR THE 800 SERIES VALVE
The purpose of the filter on the valve control package is to protect the electric solenoid valve or pressure control regulator
from debris which could clog the small flow passages. Debris stuck in the small ports of the valve or blockage of the flow
in the control package could result in failure of the valve to function. Generally, the source of water for the control package
is the upstream side of the pipe line in which the valve is installed. There are two styles of filters to select from, the INTERNAL
and the EXTERNAL filter. One or both of these filters can be selected on any control function package. Combining the use
of both the internal and external filters is possible to achieve additional filtration protection where excessive debris or solids
are present in the water. A discussion of the operation of each filter style is shown here.
EXTERNAL FILTER (option H2)
FEATURES: The external style filter is equipped with
a 1 mesh screen which gives much greater filter
screen surface area than the internal filter. This
could mean less frequent cleaning required. The
screen can be cleaned by opening the flush valve
on the end of the filter. An isolation valve is provided
so there is no need to relieve pressure on the pipe
line or drain the system to remove and thoroughly
clean the screen.
LOW TEMPERATURE CAUTION!
The flush valve needs to be open so the external
filter can drain for winter storage or if the system
water is shut off in freezing temperatures. The
internal freeze core is designed to reduce the
danger of solid ice breaking the brass housing.
Drainage is the best procedure to avoid damage. If
the valve is to be used during low temperature frost
control then the controls need to be covered. The
result of ice forming in the control tube is that the
valve can not operate correctly.
INTERNAL FILTER (option H3)
FEATURES: The internal filter is designed to self
clean. The 1 mesh screen protrudes into the
main flow of water. The flow-by of water in the
pipe may wash off debris from the screen. If the
water is fairly clean, the internal screen may never
need cleaning.
NOTE: The pipe pressure must be shut off to
remove and thoroughly clean the screen.
The internal filter (option H3) is shipped as standard.
APPENDIX B
18

Control Valve
Application
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Nelson Irrigation Corp. 848 Airport Rd. Walla Walla, WA 99362-2271 U A Tel: [phone] Fax: [phone] E-mail: [e-mail] Web site: www.nelsonirrigation.com
FLOW PATHS AND PORTS FOR CONTROL COMPONENTS
Solenoids  Solenoid valves control the automatic switching which, when electrically energized or de-energized, either
shutoff or allow flow in the control tube.
When power is off the
Nor ally Open (NO)
port is is connected to
co on. The NO port
is generally attached
to upstrea .
Manual selector valve Remote hydraulic relay
Reducing Pressure Control Sustaining Pressure Control
The same pressure co trol is used for both the reduci g a d sustai i g. O ly the port label a d hook up of the tubi g varies.
Co versio from reduci g to sustai i g is made easy by usi g the #9519 label.
APPENDIX C
When power is on the
Nor ally Closed (NC)
is connected to co on.
The NC port is attached
to the auto port of
anual selector valve.
19

ADDITIONAL INFOR ATION
Additional information is available from your irrigation dealer or from Nelson Irrigation Corporation. If you have any
questions please call 509-525-7660.
A WORD OF THANKS
Thank you for designing with NELSON IRRIGATION CORPORATION 800 Series Control Valves. Our commitment at
Nelson Irrigation Corporation is to provide you with the highest quality products. We work hard at manufacturing
and quality assurance to satisfy your requirements. We would appreciate hearing from you. If you have any suggestions
for ways to improve our products, this drip operation guide, or our service please give us a call at 509-525-7660.
WARRANTY and DISCLAI ER
Nelson Irrigation Corporation 800 Series Control Valves are warranted for one year from date of original sale to be
free of defective materials and workmanship when used within the working specifications for which the product was
designed and under normal use and service. The manufacturer assumes no responsibility for installation, removal
or unauthorized repair. The manufacturers liability under this warranty is limited solely to replacement or repair of
defective parts, and the manufacturer will not be liable for any crop or other consequential damages resulting from
any defects in design or breach of warranty.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ALL OTHER WARRANTIES, EXPRESS OR I PLIED, INCLUDING THE
WARRANTIES OF ERCHANTABILITY AND FITNESS FOR PARTICULAR PURPOSE AND OF ALL OTHER OBLIGATIONS
OR LIABILITIES OF ANUFACTURER. No agent, employee or representative of the manufacturer has authority to
waive, alter or add to the provisions of warranty, nor to make representations or warranty not contained herein.
10/01 CP 5M
Nelson Irrigation Corporation
848 Airport Road, Walla Walla, WA 99362-2271, U.S.A.
Tel: [phone] Fa : 509.525.7907 E-mail: [email protected]
www.nelsonirrigation.com