REMOTE CONTROL VALVES
The valves covered in this section will be electrically operated remote control valves (RCV’s). All remote control valves can be separated into two different types. The difference between the two is how the water enters the upper chamber. The upper chamber is the area between the cover and the top side of the diaphragm. Once the water has entered the upper chamber there are only two paths for it to escape: the manual bleed or the solenoid exhaust port.
Forward Flow - The water inters the upper chamber through a port in the center of the diaphragm. This port will normally by filtered, be sure that the filter is kept clean.
Reverse Flow - The water can enter the upper chamber in several ways. Through an external tube that runs from the pressure side to the upper chamber, through holes in the outer edge of the diaphragm, or through ports machined in the valve body.
A common misconception is that a valve stays closed because of a higher pressure above the diaphragm (the upper chamber). If there is, for example, 100 psi of static water pressure in the mainline, how can there be more than 100 psi above the diaphragm? Without a pump installed at each valve, this situation would be impossible. The valve will stay closed because the surface area above the diaphragm is roughly 2 ½ times larger than the pressurized surface area below the diaphragm. This difference causes a greater force above the diaphragm than there is below the diaphragm. Force equals Pressure times Area (Force = P x A). Water enters the valve on the pressure side (usually the side opposite the solenoid). The water will then enter and fill the upper chamber through the path detailed in the preceding section. When operating properly, this water is trapped in the upper chamber. The valve will only open once the force above the diaphragm has been relieved. This can happen in either of two ways, the solenoid has been energized by the controller, or the manual bleed has been activated.
Before assuming that there is a valve problem, check the obvious. Is the water turned on, is the controller plugged in and programmed correctly, are there isolation valves that might be turned off? Verify valve operation by using the manual bleed. This might indicate a controller or wiring problem if the valve works properly when using the manual bleed.
Valve will not close - There are two things that will cause this. The first cause is a physical obstruction (rocks or other debris) preventing the diaphragm from seating. When removing a physical obstruction, be sure to thoroughly inspect the diaphragm assembly and valve seat area for damage. The second reason is insufficient force being developed above the diaphragm. Insufficient force above the diaphragm can be caused by several things.