the Model S430 Accelerator, to provide a reduction in the
time to operate the Model A Preaction Valve following the
operation of one or more automatic sprinklers.
WARNING
The Model A Preaction Valve with Double Interlock Elec-
tric/Pneumatic Release Trim described herein must be in-
stalled and maintained in compliance with this document,
as well as with the applicable standards of the National
Fire Protection Association, in addition to the standards
of any other authorities having jurisdiction. Failure to do
so may impair the integrity of this device.
The owner is responsible for maintaining his fire protec-
tion system and devices in proper operating condition.
The installing contractor or sprinkler manufacturer should
be contacted relative to any questions.
TECHNICAL DATA
Approvals
UL and ULC Listed. FM Approved as a refrigerated area
system for use in refrigerated rooms or buildings.
NYC Accepted under MEA 271-91-M.
Working Water Pressure
20 to 175 psi (1.4 to 12.1 bar).
35 to 175 psi (2.4 to 12.1 bar) with S430 Accelerator.
Friction Loss
Refer to Figure 4.
System Air Pressure Requirements
Refer to Figure 5.
Physical Characteristics
Body components illustrated in Figure 2 are constructed
of cast iron. Internal components constructed of brass,
bronze, and stainless steel. Elastomer seals are princi-
pally EPDM and silicone.
OPERATION
As indicated in the General Description section, two inde-
pendent events resulting in opening of both the Solenoid
Valve and Dry Pilot Actuator must occur to actuate the
Model A Preaction Valve with Double Interlock Elec-
tric/Pneumatic Release Trim.
When the Model A Preaction Valve is set for service
(Fig. 3), the Differential Chamber is pressurized through
the Differential Chamber Supply Connection (Fig. 10).
The Model A Preaction Valve is a differential type valve
which depends upon the water pressure in the Differential
Chamber to hold the Clapper Assembly closed against
the water supply pressure. The Model A Preaction Valve
has a nominal trip ratio of 5 to 1, i.e., the valve operates
when pressure in the Differential Chamber is reduced to
approximately one-fifth of the water supply pressure.
Opening of both the Solenoid Valve and Dry Pilot Actua-
tor, or operating the Manual Control Station, will release
water from the Model A Preaction Valve Differential Cham-
ber faster than it can be replenished through the 3/32
inch (2.4 mm) diameter orifice of the Restrictor Assembly.
A rapid pressure drop then results in the Differential
Chamber and the differential between the Differential
Chamber and waterway is eliminated. The water supply
pressure then forces the Clapper Assembly open, permit-
ting a flow of water to the Double Interlock Preaction Sys-
tem piping. Water flowing into the system also flows to the
Waterflow Pressure Alarm Switch, which actuates the sys-
tem waterflow alarm signal.
The Model A Preaction Valve with Double Interlock Elec-
tric/Pneumatic Release Trim will automatically operate
only when both the Solenoid Valve and the Dry Pilot Ac-
tuator are open at the same time. Opening of just the Dry
Pilot Actuator (e.g., a lift truck accidentally dislodges a
sprinkler) or just energizing the Solenoid Valve (e.g., an
accidental operation of an electric pull station) will only
cause an alarm, via the low air pressure alarm switch or
the releasing panel, as applicable, to indicate that the sys-
tem requires attention. In these cases, the Model A Preac-
tion Valve will not actuate or flood the sprinkler system
piping.
As an option for water supplies of 35 psi (2.4 bar) or
more, the Model A Preaction Valve may be equipped with
a Model S430 Accelerator for the purpose of obtaining a
STAR SPRINKLER INC.
Page 4
2-4.1.10
FIGURE 4
FRICTION LOSS — 3 INCH (DN80) MODEL A VALVE
300
FLOW RATE IN GALLONS PER MINUTE (GPM)
IN POUNDS PER SQUARE INCH (PSI)
NOMINAL
PRESSURE DROP
100
200
800
400
600
0.9
0.8
0.7
1.0
2.0
3.0
4.0
6.0
5.0
7.0
FIGURE 5
AIR PRESSURE REQUIREMENTS
NOTE: Use the minimum system air pressure to decrease water
delivery time. The S460 Air Maintenance Device, via its pressure
regulator, will enable the lowest set air pressure at all times.
WATER SUPPLY PRESSURE IN PSI
AIR PRESSURE IN PSI
20
175
40
60
80
100
120
140
160
30
20
10
0
40
MINIMUM SYSTEM
AIR PRESSURE
RANGE OF ACTUA
TOR OPENING PRESSURE
OBSOLETE
