Technical data

1.3.1 Model DDX Type D
The Reliable Type D Double Interlock Preaction system utilizes a listed, normally closed (de-energized)
electric solenoid valve on the outlet of the Model DDX Deluge Valve push-rod chamber. The solenoid
provides a separation between the hydraulically pressurized push-rod chamber and atmospheric pres-
sure drain tubing. When the programming logic of the release panel has been satisfied, the panel
opens (energizes) the solenoid valve. Pressure is relieved from the push-rod chamber allowing the
Model DDX Deluge Valve to open and flow water into the protected area. The Type D system is de-
scribed as an electric/electric double interlock preaction system. Two independent conditions must
coexist to satisfy the double interlock programming in the release panel. For the Type D system, these
two conditions are (a) activation of the detection system and (b) signal of low pneumatic pressure in
the system piping. Detection systems are more sensitive than the sprinklers on the system, and will ac-
tivate prior to the sprinklers opening. The time period between fire detection/alarm and opening of the
sprinklers from heat allows the building owner a chance to respond and possibly avoid unnecessary
discharge of water into the water sensitive environment. In the event the alarm is not attended to, the
fire will continue to grow eventually fusing one or more sprinklers and relieving pneumatic pressure in
the system. Loss of pneumatic pressure results in a signal from the pressure switch. When this second
condition (low pneumatic pressure signal) coexists with the first condition (detection), the release panel
energizes (opens) the solenoid valve, in turn actuating the Model DDX Deluge Valve flowing water into
the protected area. Alarm devices are activated upon the flow of water into the sprinkler system piping.
Pneumatic pressure can be provided from a tank-mounted compressor, plant air system, or nitrogen
cylinders, and must be maintained by a Reliable Model A-2 listed pressure maintenance device*.
Pneumatic pressure is monitored by a pressure switch* that will notify the owner in the event of falling
pressure due to sprinkler damage, pipe damage, or failure of the compressed gas system. A low pres-
sure condition in the absence of a detection signal or a detection signal in the absence of a low pres-
sure condition will NOT result in activation of the solenoid and main system control valve. The singular
condition can be corrected and the system returned to normal service.
*Note: For Type D systems, the Reliable Model A-2 Pressure Maintenance Device and the System Sensor
Model EPS 10-2 Pressure Switch are provided with the trim.
Approvals and technical data for Model DDX Type D Double Interlock Preaction systems can be found
on Reliable Automatic Sprinkler Company Bulletin 750.
14.
Figure 12