2
General
Type D Double Interlock Preaction Systems are designed
for water sensitive areas that require protection from
inadvertent water flow into the sprinkler system piping, but
where a mechanical backup for the electric release is not
required. Typical applications for this type of trim are libraries
and computer server rooms.
To flow water into a Type D Double Interlock Preaction
System, two events must take place. A fire detection device
must operate, and the low pressure switch must be operated
by the loss of system air or nitrogen pressure due to sprinkler
operation (see note 1 below). These two signals must coexist
at the releasing control panel, which only then will energize
the normally closed solenoid valve (175 psi (12.1 bar) or
300 psi (20.7 bar) rated), causing the water flow into the
system.
These systems utilize fire detection devices and system
air pressure as separate zones (inputs) to a cross-zoned
releasing control panel. The solenoid releasing valve remains
closed until energized by the releasing control panel. This will
occur only when both a fire detection device is operated and
the low air pressure switch has detected sufficient loss of
system air pressure (sprinkler operation).
In the event that the system piping is ruptured, or a sprinkler
head is accidentally opened, the low air pressure switch will
operate and an alarm will sound. The Model DDX Deluge
Valve, however, will not be released to flow water since
the solenoid valve remains closed due to the cross-zoned
control panel configuration. The same result would occur if a
fire detection device were falsely operated. The control panel
will activate an alarm, however again, the Model DDX Deluge
Valve will not flow water due to the cross-zoned control panel
configuration.
This requirement for both a detector to operate and the loss
of system air pressure before the Model DDX Deluge Valve
releases water into a preaction system assures maximum
protection against inadvertent water flow before a sprinkler
is open.
At the heart of Reliable’s Type D Double Interlock Preaction
System is the Model DDX Deluge Valve. This Deluge Valve
is a hydraulically operated, straight through design, latching
type valve (see Fig. 1). System maintenance is simplified
since the Model DDX Deluge Valve can be reset externally
without cover removal. This is accomplished by pushing in
and turning the external reset knob at the rear of the Deluge
Valve (see Fig. 1). This feature provides a significant system
restoration time advantage.
The Reliable Model DDX Type D Double Interlock Preaction
System trim set (see Fig. 2 & Fig. 3) provides all of the
necessary equipment for connections to the Model DDX
Deluge Valve’s pushrod chamber inlet and outlet ports, a 1-
1
/
4
"
(30 mm) main drain on 2" (50 mm), 2-
1
/
2
" (65 mm), 76 mm
and 3" (80 mm) valve sizes or a 2" (50 mm) main drain on
4" (100 mm), 165 mm, 6" (150 mm) and 8" (200 mm) valve
sizes, alarm devices, air supply, water supply and required
pressure gauges. This trim set is available in individual (loose)
parts, in time-saving, segmented assembled kit forms or fully
assembled to the Model DDX Deluge Valve (with or without
a control valve).
Listings & Approvals:
(Only when used with Reliable’s Trim Sets.)
1. Reliable’s Type D Double Interlock Preaction Systems
2" (50 mm), 2-
1
/
2
" (65 mm), 76 mm and 3" (80 mm), 4"
(100 mm), 165 mm, 6" (150 mm) and 8" (200 mm) are
Factory Mutual Approved Refrigerated Area Sprinkler
Systems for use in refrigerated rooms or buildings.
Refrigerated area sprinkler systems are FM Approved as
complete systems. Systems are FM Approved for use
with thermal detectors and Class A detector wiring only.
2. Reliable’s Type D Double Interlock Preaction Systems
2" (50 mm), 2-
1
/
2
" (65 mm), 76 mm, 3" (80 mm), 4"
(100 mm), 165 mm, 6" (150 mm) and 8" (200 mm) are
Underwriters Laboratories, Inc. Listed and UL certified
for Canada (cULus) in the Special System Water Control
Valve-Double Interlock Type (VLJH) category.
3. The NYC acceptance number for this system is MEA
258-93-E.
The Reliable Model DDX Type D Double Interlock Preaction
System is UL Listed and FM Approved only when used with
the trim components shown in Fig. 2 & 3.
Note 1:
Wherever the word “air” is used in this bulletin
as a reference to the pneumatic pressure source it shall
also mean “air or nitrogen.”
System Operation
When set correctly for service, the Model DDX Deluge
Valve is hydraulically established to withhold the supply water
from the sprinkler system piping. The Reliable Model DDX
Deluge Valve is shown in both closed and open positions in
Fig. 1. In the closed position, the supply pressure acts on the
underside of the clapper and also on the push rod through the
push rod chamber’s inlet restriction. The resultant force due
to the supply pressure acting on the push rod is multiplied
by the mechanical advantage of the lever and is more than
sufficient to hold the clapper closed against normal supply
pressure surges.
Whenever a fire and a low system air pressure condition
are detected, the energized solenoid valve vents the push
rod chamber to atmosphere through the chamber’s outlet.
Since the pressure can not be replenished through the inlet
restriction as rapidly as it is vented, the pushrod chamber
pressure falls instantaneously. When the pushrod chamber
pressure approaches approximately on-third of the supply
pressure, the upward force of the supply pressure acting
beneath the clapper overcomes the lever applied force,
thereby opening the clapper.
Once the clapper has opened, the lever acts as a latch,
preventing the clapper from returning to the closed position.
Water from the supply flows through the Deluge Valve into
the sprinkler system piping. Water also flows through the
Deluge Valve alarm outlet to the alarm devices.
After system shutdown, resetting the Model DDX Deluge
Valve is quite simple. Doing so only requires pushing in and
turning the reset knob at the rear of the valve (see Fig. 1). The
external reset feature of the Model DDX Deluge Valve provides
a means for simple, economical system testing, which is one
essential facet of a good maintenance program. The external
