9
hours. In addition to the hydrostatic tests described above,
dry pipe and double interlock preaction systems require an
additional low pressure air test.
In some cases, hydrostatic testing (in accordance with the
NFPA 13 requirements noted above) will result in pressures
that exceed the working pressure of the valve and trim kit
for the two-hour test period.
The valve and applicable
trim kit have been tested, approved and listed under
these conditions and as such, hydrostatic testing in
accordance with NFPA 13 is acceptable. In addition, the
clapper can remain in the closed position and the trim
kit need not be isolated, as each has been designed to
withstand hydrostatic testing as required by NFPA 13.
Hydrostatically testing the valve and trim to pressures
higher than their rating is limited to the hydrostatic test
as referenced by NFPA 13. It does not address the
occurrence(s) of a “water hammer” effect, which can
indeed damage the valve. A “water hammer” in the
water supply piping of the valve can create pressures in
excess of the rated pressure and should be avoided by
all necessary means. This condition may be created from
improper fire pump settings, underground construction
work, or an improper venting of trapped air in the water
supply piping.
System Design Considerations
The automatic sprinklers, air compressor, releasing devices,
electric releasing control equipment, fire detection devices,
manual pull stations, and signaling devices which are utilized
with the Type D Double Interlock Preaction System must be
UL or ULC Listed or FM Approved, as applicable.
Factory Mutual requires that detection devices in
refrigerated areas be of the fixed temperature type. In
addition, they must have a temperature rating lower than that
of the sprinklers and preferably as low as possible for the
given ambient conditions.
The Deluge Valve, and all interconnecting piping must be
located in a readily visible and accessible location and in an
area that can be maintained above 40 °F (4 °C).
Note:
Heat
Tracing is not permitted.
Pendent sprinklers, other than dry pendents, used on
preaction systems shall be installed on return bends per
NFPA 13.
The solenoid valve is operated and supervised by the
electrical releasing/control panel. Details on the electrical
portion of this system can be found in Reliable Bulletin 718,
“Solenoid Valves”.
System Air Pressure Requirements
In accordance with NFPA 13, Double Interlock Preaction
Systems require a minimum of 7 psi (0.5 bar) pneumatic
pressure to supervise the sprinkler system. The Model A-2
Pressure Maintenance Device is used to maintain the system
pneumatic pressure between 7 and 10 psi (0.5 and 0.7 bar)
where a dry nitrogen gas supply or a clean, dependable and
continuous (24 hours a day, 7 days a week) compressed air
source is available.
To adjust the system pneumatic pressure between 7 and
10 psi (0.5 and 0.7 bar) refer to Reliable Bulletin 254. The low
air pressure alarm switch (item #5, Fig. 2 or item #5, Fig. 3) is
factory set to operate between 5 and 6 psi (0.3 and 0.4 bar)
with decreasing pressure. If necessary, adjustments can be
made by following the manufacturer’s adjustment procedure
as described in the installation and maintenance instructions
enclosed with the switch.
Note:
The dew point of the air must be maintained below the
lowest ambient temperature to which the double interlock
preaction system piping will be exposed. Introduction of
moisture into the system piping that is exposed to freezing
temperatures can create ice blockage, which could prevent
proper operation of the sprinkler system. As a minimum,
the supply of air should be taken from the refrigerated area
at the lowest temperature. The air supply system must be
carefully designed to prevent plugging by frost deposits.
Special requirements such as those in FME&R’s “installation
Guidelines for Refrigerated Storage” may need to be
incorporated.
Each Type D Double Interlock Preaction system is provided
with a Model A-2 Pressure Maintenance Device for individual
monitoring of pneumatic pressure and proper operation of
the system. The Model A-2 Pressure Maintenance Device
requires
a tank mounted air compressor.
System Electrical Requirements
All releasing and detection devices in Reliable’s Model DDX
Type D Double Interlock Preaction System are operated and
supervised by the PFC-4410-RC Releasing Control Panel
in accordance to the wiring diagram shown in Fig. 5. the
releasing control panel should be set to use Program #11
(see Potter Instruction Manual #5403550).
The power supply, the standby emergency power supply,
battery charger, and the rectifier circuitry are all contained
within the Potter PFC-4410-RC Releasing Control Panel.
Batteries that provide ninety hours of standby power are
required for Factory Mutual Approved systems.
The Model BNG-1 Manual Emergency Station can be
connected as a simple detector for fire annunciation, or the
Model BNG-1F can be connected to both zones for total
system emergency manual operation.
The solenoid valve is operated and supervised by the
Potter PFC-4410-RC Releasing Control Panel. Potter PFC-
4410-RC Releasing Control Panel requires 120 V ac.
Note:
In order for the solenoid valve to maintain Reliable’s
warranty it must remain sealed as it came from the factory.
If there are concerns about the valve’s internal components,
immediate replacement is recommended.
Standard Solenoid Valve Specifications:
Skinner Model 73218BN4UNLVN0C111C2
Rated working pressure: 175 psi (12.1 bar)
Voltage: 24 V dc
Power: 10 W
Current: 0.41 Amps Holding
Enclosure Coil: NEMA 4X
Pipe Size:
1
/
2
" NPT Female
Cv Factor: 4.0
