Reliable Automatic Sprinkler Co., Inc.,
103 Fairview Park Drive, Elmsford, New York 10523
Model DDX-LP PrePak System
2” (50mm), 2
1
/
2
” (65mm),
3” (80mm), 4” (100mm),
6” (150mm) & 8” (200mm)
Bulletin 748 July 2019
Bulletin 748 July 2019
Instructions for
Installation, Operation,
Care and Maintenance
Low Pressure Dry-Pipe System
10 psi - 26 psi (0.7 bar - 1.8 bar)
Recommended System Pressure
General Description
The Reliable Model DDX-LP PrePak (Sizes 2” (50mm),
2½” (65 mm), 3” (80 mm), 4” (100 mm), 6” (150mm) and
8” (200mm)) is a completely self-contained, supervised dry
pipe system that can be readily installed within a floor space
of less than 7 square feet (0.65 square meters). Refer to Fig.
1 for cabinet dimensions. Installation of the DDX-LP PrePak
requires just three piping connections: the water supply, the
sprinkler system and the drain. Reference locations of these
piping connections are shown in Fig. 1. One electrical sup-
ply connection is required.
Note:
The Model DDX-LP PrePak
is available with an optional 115V VAC (60Hz) air compres-
sor.
Full assembly drawings for the units are available on the
Reliable Automatic Sprinkler Company website (www.reli-
ablesprinkler.com).
The heart of the Reliable Model DDX-LP PrePak is the
Model DDX-LP Dry Pipe Valve. The Reliable Model DDX-LP
Dry Pipe Valve is a hydraulically operated, differential-type
valve designed for use as a primary control valve in a low
pressure dry pipe valve system. The trim set used with the
Model DDX-LP Dry Pipe Valve contains the Reliable Model
LP Dry Pilot Actuator releasing device. This Actuator allows
the system air or nitrogen pressure to be considerably less
than the water supply pressure (see Table A). The following
benefits are a direct result of lower air pressure:
1. In refrigerated area systems, lower air pressure de-
creases the possibility of ice plugs that could impede
or prevent the flow of water to fire sprinkler heads in
the event of fire.
2. Lower air pressure allows for smaller capacity, lower
cost dehydration equipment, where required.
3. Lower air or nitrogen pressure can reduce water de-
livery time when the system actuates, and in some
cases, may eliminate the need for an accelerator.
4. For systems supplied with nitrogen, low supervisory
pressure reduces the quantity of nitrogen required to
maintain the system pressure.
Note: Photograph is for illustrative purposes only.
