Potter Releasing Systems - Manual (Page 34)

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Installation of Valve Supervisory Switches
The main reason for sprinkler system failure is due to the water control valves being closed. Therefore, every
water control valve that can disable any portion of a sprinkler system should be electrically supervised in the
open position.
The main types of valves used are, outside screw and yoke [OS&Y], butterfly and wall or post indicator
[PIV] valves.
OS&Y valves have a large handwheel with a threaded shaft through the center of the handwheel. There is also
a bracket or “yoke” that runs on both sides of the threaded shaft, from the body of the valve to the handwheel.
When the valve is open, the shaft protrudes through the handwheel. As the valve is closed, the shaft is being
screwed into the body of the valve. Most tamper switches for these valves mount on the yoke of the valve using
either “J” hooks or carriage bolts and a mounting bracket. The switches have a “trip rod” that rests in a groove
on the threaded shaft of the valve. Some valve manufacturers put the groove on the stem, with other valves the
installer must file a 1/8” deep groove using a 3/8” rat tail, (round not tapered), file. As the valve is closed, the
trip rod rises out of the groove and trips the switch. The switch must stay tripped throughout the entire travel of
the valve. It must not alternate between “tripped” and “normal” as the trip rod is rolling across the threads of the
stem. The switch must also trip if the switch is removed from the valve.
Post Indicator Valves use a different switch than OS&Y valves. For PIV valves, the switch screws into a 1/2”
NPT fitting on the side of the valve. The switch has a trip rod that rides on the target of the valve. The target is
the portion of the valve that shows “open” or “shut”. When the valve is fully open, the target should be pushing
the trip rod against the spring force of the rod. As the valve is closed, the spring force causes the rod to follow
the target of the valve, tripping the switch.
Butterfly Valves use the same switch as PIV valves. It also screws into a 1/2” NPT fitting on the valve. The
trip rod is operated by a cam inside of the valve that rotates as the valve is closed. Partially close the valve,
remove the nipple from the switch and screw it into the valve. Loosen the set screw that holds the trip rod in the
housing and extend the trip rod. Slide the PCVS over the nipple, observing which direction the rod will move
when the valve is closed. Orient the device so the cam of the valve is pushing against the spring force of the
PCVS when the valve is open. As the trip rod touches the cam, it will push the trip rod back into the housing.
If the trip rod is too long, remove the rod from the switch housing, note that there is a groove cut into the rod
1” from the end of the rod that was in the housing, this can be broken off with a pair of pliers. After the cam of
the valve pushes the trip rod back into the housing, remove the PCVS and slide the trip rod 1/32” farther into
the housing before tightening the set screw. This will prevent any imperfections on the cam from affecting the
operation of the PCVS. Slide the PCVS over the nipple and tighten the set screw.
Ball Valves. The Potter Model RBVS can be used to supervise ball valves.
Special Valves. For non-rising stem valves a “plug type switch” can be used. These are switches that are UL
listed for special applications and are subject to the approval of the authority having jurisdiction. A receptacle is
mounted on a wall or section of pipe, a plug with a length of cable is plugged into the receptacle. The other end
of the cable is looped through the handwheel of the valve or through a hole drilled into the handle of the valve,
then hard wired back into the receptacle. When the valve is closed it unplugs the plug from the receptacle and
trips a switch. If the cable is cut it also opens the circuit. The cable must be stretched tight enough so operation
of the valve will cause the plug to pull out of the receptacle.
Note: Valve supervisory switches shall trip within 2 revolutions of the handwheel, or 1/5 of the travel of the
valve, per NFPA72 2010 17.16.1.2.