II.
ELECTRONICALLY ACTUATED PRESSURE REDUCING VALVE
1.
INTRODUCTION
The PRV-71H (electronically operated) is an electronically actuated, spring loaded diaphragm type gas pres-
sure reducing and shut-off valve. Its purpose is to reduce and control downstream pressure between 15 to 45
psig. The outlet pressure is manually adjusted by the position of the lock nuts. The electronic actuator is spring
loaded normally closed and upon loss or disconnection of power, then the spring will move the pressure reduc-
ing valve to the closed position. Upon recieving or restoring power, the electronic actuator will close an inter-
nal solenoid valve and start an internal motor driven pump that is used to force the ram down until it reaches the
manually set operating position.
2.
INSTALLATION
Because of its weight the PRV-71H (electronically operated) should always be supported. An optional wall-
mounting bracket is available for fast and easy installation. This wall mounting bracket includes four
3
⁄
8
"x 1"
mounting slots. The PRV should be installed in the upright position.
Inlet and outlet connections to the pressure reducing valve are
3
⁄
4
" or 1" FNPT depending on the model chosen.
A label is provided to indicate the direction of fl ow and help identify the inlet and the outlet. There is also a
1
⁄
4
" FNPT vent connection above the outlet connection in case of diaphragm failure and it is recommended that
1
⁄
2
" schedule 80 carbon steel vent piping be used. Vent piping should also slope downward at least 2 degrees to
prevent water/moisture entry and an insect screen must be installed on the vent pipeline outlet to prevent insects
from blocking the pipeline.
The installation of this valve should be downstream of any chlorine fi lters and drip legs, and a pressure gauge
should be mounted on the downstream side of the valve to monitor outlet pressure.
Depending on the model, the electronic actuator will require either a 120 or 240 VAC (50/60 Hz) single phase
power supply connected to the line terminals on the actuator unit with the ground line connected to the screw
underneath the common (COM). The unit also includes a contact relay offering both normally open (N.O.) and
normally closed (N.C.) connections, and their proper wiring location can be seen on the valve. To get remote
closure of the actuator based on an alarm condition, wire a SPST switch into the L1 (phase) side of the power
line. When operating, the valve operator requires 170 VA.
3.
OPERATION
With voltage applied to the electronic actuator, an internal solenoid valve will close and a motor driven pump
will apply pressure to a spring loaded piston. The ram valve which is connected to this piston will move down
into position set by the lock nuts. Once the lock nuts hit the bottom of the yoke, the resistance will be picked
up by the actuator and the motor will stop, holding the ram valve in place. Thus, the downstream pressure is set
by the position of the lock nuts. Lowering the lock nuts will reduce the amount of tension applied to the load-
ing spring, lowering downstream pressure, while raising the lock nuts will increase the tension applied to the
loading spring, increasing the downstream pressure.
Warning:
Do not adjust the lock nuts while the actuator is on. Doing so will result in damage of the actuator.
To adjust the outlet pressure remove from power source and adjust, then re-apply power to get new pressure set-
ting. Repeat until the correct outlet pressure is achieved
When in position, the ram valve compresses an internal spring, which in turn presses down on a diaphragm and
opens up the orifi ce between the valve seat and valve plug. This opening allows for gas to enter through the
reducing valve at a controlled pressure. Downstream pressure is regulated by the counteracting forces on the
diaphragm between the spring and the gas. For example, when fl ow demand is increased there will be less force
acting up on the diaphragm. This will allow the spring to expand down more, enlarging the orifi ce and allowing
more gas fl ow into the regulator in order to establish a new diaphragm equilibrium position.
When power is lost, the solenoid valve will open and the ram valve will go up out of contact with the loading
spring. This removes tension on the loading spring, causing the diaphragm to move up and the pressure reduc-
ing valve to close.
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