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OVERVIEW
This instructional page will cover several aspects regarding lawn sprinkler Control Valves.
Because control valves vary in design from model to model, these instructions will stick with general concepts.
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Control Valves - What are they and why do we need so many?
Lawn sprinkler control valves are used to control the flow of water throughout your lawn sprinkler system.
These valves are controlled by your sprinkler timer via a 24 volt a/c signal through copper wire.
They can also be opened and closed manually.
Lawn sprinkler control valves consist of the following components: electric solenoid, manual bleed screw, cap/lid, spring, diaphragm, and lower housing.
There are two reasons you need several control valves in your sprinkler system.
The main reason is water supply.
Most homes simply do not have a water supply large enough to run the entire system at once.
Control valves break your system into zones based on the available water supply.
You timer cycles through the entire system opening one valve at a time.
The second reason you use valves is for control - hence the name control valve.
This allows you to have a sunny area controlled by one valve and a shady area controlled by a separate valve.
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How do Control Valves work?
Control valves open and close based on water pressure (specifically pressure differences).
There are two main areas inside the valve called the "upper chamber" and "lower chamber."
These two chambers are separated by the diaphragm.
Water flows into and fills the lower chamber.
A small tube in the middle of the diaphragm allows water to flow from the lower chamber into the upper chamber.
At this point water has filled the upper and lower chambers and water pressure is equal on both sides of the diaphragm.
Now we must consider
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2400T Breakout
Upper Chamber
Lower Chamber
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the force of the spring pressing on the top side of the diaphragm.
The force from the spring creates a pressure imbalance (the pressure is greater on top) and the diaphragm is held closed.
This is the valve's resting "normally closed" state.
In order for the valve to open we must relieve pressure on top of the diaphragm.
This is done electronically by the timer via the solenoid OR manually via the manual bleed screw.
In either case, when pressure is relieved on top of the diaphragm the water pressure from the lower chamber (your house water supply) pushes the diaphragm up and water spills over the lower chamber walls and flows out to the sprinklers.
The valve will stay open until pressure is re-applied to the top of the diaphragm.
When the timer cuts power to the valve's solenoid the pressure is instantly re-applied to the top of the diaphragm, the valve closes, and returns to its resting noramally closed state.
When the valve is opened manually and the manual bleed screw is tightened, it may take several minutes for pressure to build up on top of the diaphragm and the valve to close.
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How do I wire my control valves?
Most sprinkler control valves are equipped with a 24 volt a/c solenoid.
Typically control valves are grouped together in 2's, 3's, or 4's and placed inside a protective valve box.
Sometimes valves are scattered throughout the system and placed in singular valve boxes or buried directly in the ground without a protective box.
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Step 1
Step 2
Step 3
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Grouping valves makes wiring easier, lowers costs, and also makes servicing easier.
The basic concept for wiring is very simple; connect one valve wire to the hot lead (numbered terminal) in the timer and connect the other valve wire to the common ground ("c" or "comm") in the timer.
You can run two wires for each valve in your system OR you can run several hot wires (one per valve) and a single common wire that all the valves share.
Multi-strand wire is used in the latter situation and makes wiring easier and cost less.
Multi-strand wire has several colored wires wrapped in an outer protective sleeve.
Typically the white wire is used as the common ground wire.
When wiring make note of what color wire is connected to each valve so you can connect the wires in your desired order at the timer.
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What is flow control?
Some valves will have a built in flow control device.
A flow control device does exactly what it is named for - it controls the flow of water through the valve.
A flow control device is simply a mechanical device that restricts the amount a diaphragm will open.
The diaphragm can be restricted 0-100% by the flow control device.
Without a flow control device a valve is either 100% open or 100% closed.
A flow control device is usually a handle or a screw located on top of the valve.
Turning the flow control device clockwise will decrease the flow through the valve.
Conversely, turning the flow control device counterclockwise will increase flow through the valve.
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©2003 Pioneer Midwest Inc.
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