I-768N
/ Series 768N FireLock NXT
™
Dry Valve
/ Installation, Maintenance, and Testing Manual
AIR SUPPLY REQUIREMENTS
The required air pressure for Series 768N FireLock NXT Dry Valves is 13 psi/90 kPa/0.9 Bar minimum, regardless of the system supply water
pressure. Normal air pressure should not exceed 20 psi/138 kPa/1.4 Bar. Failure to maintain air pressure within the 13 psi/90 kPa/0.9 Bar to
18 psi/124 kPa/1.2 Bar range may delay system operation response time.
The Series 746-LPA Dry Accelerator must be used only on systems operating below 20 psi/138 kPa/1.4 Bar of air. If air pressure is higher than
20 psi/138 kPa/1.4 Bar, the Series 746 Dry Accelerator should be used.
FOR VdS APPROVED VALVES ONLY:
The minimum air pressure for Series 768N FireLock NXT Dry Valves installed with Series 746-LPA Dry
Accelerators shall be 16 psi/110 kPa/1.1 Bar. The maximum air pressure shall be 19 psi/130 kPa/1.3 Bar.
If multiple Series 768N FireLock NXT Dry Valves are installed with a common air supply, isolate the systems with a spring-loaded, soft-seated ball
check valve to ensure air integrity for each system. Good practice is to include a ball valve for isolation and service of each individual system.
The engineer/system designer is responsible for sizing the compressor so that the entire system is charged to the required air pressure within
30 minutes. DO NOT oversize the compressor to provide more airflow. An oversized compressor will slow down or possibly prevent valve operation.
If the compressor fills the system too fast, it may be necessary to restrict the air supply. Restricting the air supply will ensure that air being exhausted
from an open sprinkler or manual release valve is not replaced by the air supply system as fast as it is being exhausted.
BASE- OR RISER-MOUNTED AIR COMPRESSORS
For base- or riser-mounted air compressors, the recommended air pressure of 13 psi/90 kPa/0.9 Bar is the “on” or “low” pressure setting for the
compressor. The “off” or “high” pressure setting should be 18 psi/124 kPa/1.2 Bar.
When a base- or riser-mounted air compressor supplies air to a Series 768N FireLock NXT Dry Valve, it is not necessary to install the Victaulic Series
757 Regulated Air Maintenance Trim Assembly (AMTA). In this case, the air line of the compressor connects to the trim at the fitting where the Series
757 Regulated AMTA is installed normally (refer to the applicable trim drawing). If the compressor is not equipped with a pressure switch, the Series
757P Air Maintenance Trim Assembly with Pressure Switch should be installed.
NOTICE
• Victaulic recommends a maximum of two Series 768N FireLock NXT Dry Valves per Series 757 Regulated AMTA or Series 757P AMTA with
Pressure Switch.
SHOP AIR OR TANK-MOUNTED AIR COMPRESSORS
In the event a compressor becomes inoperative, a properly sized tank-mounted air compressor provides the greatest protection for systems.
When shop air or a tank-mounted air compressor is used, the Series 757 Regulated AMTA must be installed. The Series 757 Regulated AMTA
provides proper air regulation from the air reservoir to the sprinkler system.
For tank-mounted air compressors, the recommended air pressure of 13 psi/90 kPa/0.9 Bar should be used as the set point for the air regulator. The
“on” pressure of the compressor should be at least 5 psi/34 kPa/0.3 Bar above the set point of the air regulator.
COMPRESSOR REQUIREMENTS AND SETTINGS FOR A SERIES 768N FIRELOCK NXT DRY VALVE
INSTALLED WITH A SERIES 746-LPA DRY ACCELERATOR
Set the air regulator of the Series 757 Regulated AMTA to a minimum of 13 psi/90 kPa/0.9 Bar.
FOR VdS APPROVED VALVES ONLY:
The minimum air pressure for Series 768N FireLock NXT Dry Valves installed with Series 746-LPA Dry
Accelerators shall be 16 psi/110 kPa/1.1 Bar. The maximum air pressure shall be 19 psi/130 kPa/1.3 Bar.
The Series 757P Air Maintenance Trim Assembly with Pressure Switch MUST NOT be used on a Series 768N FireLock NXT Dry Valve installed
with a Series 746-LPA Dry Accelerator, unless a tank and air regulator are added.
In the event a compressor becomes inoperative, a properly sized tank-mounted air compressor provides the greatest protection for systems installed
with a Series 746-LPA Dry Accelerator. In this situation, air can be supplied continuously to the sprinkler system for an extended time period.
NOTE:
The Series 757 Regulated AMTA should be used with a tank-mounted air compressor to supply air to a Series 768N FireLock NXT Dry Valve
when the Series 746-LPA Dry Accelerator is used. The use of an air regulator with a base- or riser-mounted air compressor could cause short cycling,
resulting in premature wear of the compressor.
The air regulator of the Series 757 Regulated AMTA is a relief-type design. Any pressure in the system that is above the set point of the air regulator
will be released. Therefore, charging the air regulator above the set point could cause premature operation of a valve installed with a Series 746-LPA
Dry Accelerator.
SETTINGS FOR AIR SUPERVISORY PRESSURE SWITCHES AND ALARM PRESSURE SWITCHES
1.
Air supervisory pressure switches are required for dry systems and must be set according to the following notes.
NOTE:
Switches for VQR
assemblies are pre-set at the factory.
1a.
Wire the air supervisory pressure switches to activate a low-pressure alarm signal.
NOTE:
In addition, the local authority having jurisdiction
may require a high-pressure alarm. Contact the local authority having jurisdiction for this requirement.
1b.
Set the air supervisory pressure switches to activate at 2 – 4 psi/14 – 28 kPa/0.1 – 0.3 Bar below the minimum air pressure required (but
not lower than 10 psi/69 kPa/0.7 Bar).
1c.
Wire the alarm pressure switch to activate a water flow alarm.
1d.
Set the alarm pressure switch to activate on a pressure rise of 4 – 8 psi/28 – 55 kPa/0.3 – 0.6 Bar.
I-768N_9
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