Training Manual - Potter Electric Signal Company, LLC
Training Manual - Potter Electric Signal Company, LLC
Training Manual - Potter Electric Signal Company, LLC
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#2. Wet System With An Alarm Check Valve:<br />
This type of system has an alarm check valve, the valve is basically a check valve with an alarm port. The main<br />
purpose of the alarm check valve is to ring a mechanical bell called a water motor gong. The valve should, (if<br />
properly maintained), help hold the system pressure steady and reduce the possibility of false alarms. Under<br />
normal circumstances, the clapper of the valve is closed, blocking the alarm port, maintaining the system<br />
pressure, and preventing the sprinkler system water from leaking back into the city supply. When a sprinkler<br />
opens due to fire, or there is a large surge in the city pressure, the clapper of the valve opens. The alarm port is<br />
now exposed to the incoming water supply. When the pressure at the switch reaches 6 psi, the pressure switch<br />
trips, or the retard time starts on the pressure switch with built in retard. This alarm port may be piped to the<br />
outside of the building through a water motor gong.<br />
These systems can use a vane type flow switch with a retard or they can use a pressure type flow switch. The<br />
pressure type flow switch would be installed on the alarm port, in line with a water motor gong if one is being<br />
used. The pressure switch must either be installed on top of a retard chamber, (see Fig. 3), or a pressure switch<br />
with a built in retard, (see Fig. 4), must be used to prevent false alarms due to water surges. There must be an<br />
automatic drain on this line to allow the water to drain and the pressure to drop back to zero so the pressure<br />
switch can reset after a surge or activation of the alarm valve.<br />
Pressure type flow switches can be installed without disabling the sprinkler system. Since they are installed on<br />
the alarm port, there is no pressure or water present under normal circumstances. The sprinkler system does not<br />
have to be drained, they can be installed without shutting off the water supply. Therefore the sprinkler system is<br />
never out of service.<br />
Retard chambers are metal containers that fill with water when there is a surge in city pressure. They absorb<br />
the pressure increase thereby allowing the pressure switch to only operate in an actual alarm condition. There<br />
is an automatic drain at the bottom of the chamber to allow the surge to drain out. Retard chambers require<br />
maintenance to make sure that the drain stays clear and doesn’t get clogged with rust or corrosion. If a surge<br />
does not drain from the retard chamber before another surge happens, the retard chamber may fill causing the<br />
pressure switch to send a false alarm.<br />
Fig. 3<br />
Pressure Type Flow Switch Installed On Top Of Retard Chamber<br />
WATER<br />
PRESSURE<br />
GAUGE<br />
(SYSTEM<br />
PRESSURE)<br />
BY-PASS LINE<br />
CHECK VALVE USED TO<br />
BUILD SYSTEM PRESSURE<br />
FROM SMALL SURGES<br />
WATER PRESSURE GAUGE<br />
(CITY PRESSURE)<br />
TAMPER<br />
DEVICE<br />
OSYSU<br />
OSY CONTROL VALVE (OPEN)<br />
(OPEN)<br />
(OPEN)<br />
RISER TO<br />
SPRINKLER HEADS<br />
CHECK<br />
WATER BY-PASS<br />
TEST VALVE<br />
(CLOSED)<br />
ANY SHUT-OFF VALVE IN<br />
LINE WITH A PRESSURE<br />
SWITCH IS REQUIRED TO BE<br />
SUPERVISED PER NFPA 72<br />
DRAIN<br />
VALVE<br />
(CLOSED)<br />
RBVS<br />
CHECK<br />
VALVE<br />
STRAINER<br />
WATERFLOW<br />
SWITCH<br />
PS10-1<br />
PS10-2<br />
DRIP<br />
CUP<br />
TO WATER<br />
MOTOR<br />
GONG<br />
RETARD<br />
CHAMBER<br />
DRAIN<br />
A pressure switch with a built in retard allows the system to remain operational at all times, and eliminates the<br />
maintenance required on the retard chamber. An automatic drain is still required to relieve the pressure on the line.<br />
WATER PRESSURE FROM<br />
CITY MAINS<br />
DRAIN<br />
PIPE<br />
Note: All water control valves shall be supervised per NFPA13 2010 8.16.1.1.2.1. Pressure type flow switches<br />
must be installed before any shut-off valve, or such valve must be electronically supervised.<br />
Note:<br />
Unless excess pressure is pumped into system, the waterflow device should have a retard per NFPA 72 2010<br />
17.12. There shall be no shut-off valve in line to a pressure type waterflow switch, unless the shut-off is<br />
electrically supervised. The <strong>Potter</strong> Model RBVS is designed to electrically supervise ball valves.<br />
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