Victaulic FireLock NXT 769 Series User manual

HANG THESE INSTRUCTIONS ON THE
INSTALLED VALVE FOR EASY FUTURE REFERENCE
WARNING
• Failuretofollowinstructionsandwarningscancauseproduct
failure,resultinginseriouspersonalinjuryandpropertydamage.
• Readandunderstandallinstructionsbeforeattemptingto
installanyVictaulicpipingproducts.
• Wearsafetyglasses,hardhat,andfootprotection.
• Savethisinstallation,maintenance,andtestingmanualfor
futurereference.
Ifyouneedadditionalcopiesofanyliterature,orifyouhaveany
questionsconcerningthesafeinstallationandoperationofthis
product,contactVictaulic,P.O.Box31,Easton,PA18044-0031,
USA,Telephone:1-800PICKVIC,e-mail:[e-mail].
WARNING
SERIES 769
PreactionElectricAutoConvertDryTrim
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL I-769P.AC/ELEC
FireLockNXT™AutoConvertPreactionValve
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
REV_B

TABLEOFCONTENTS
HazardIdentification......................................1
Installer Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
General..............................................2
MaintenanceandTesting.................................2
Introduction.............................................2
TrimDimensions .........................................3
Exploded View Drawing – Trim Components . . . . . . . . . . . . . . . . . . . . 4
Exploded View Drawing – Internal Valve Components. . . . . . . . . . . . . . 6
Description - AutoConvert Trim Assembly . . . . . . . . . . . . . . . . . . . . . . 7
Latching Solenoid Module Cutaway . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Section View Drawing and Description –
Series 776 Low-Pressure Actuator . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Section View Drawing and Description –
Series 746-LPA Dry Accelerator. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
AirSupplyRequirements..................................10
CompressorSizing.....................................10
Base or Riser-Mounted Air Compressors . . . . . . . . . . . . . . . . . . . . 10
Victaulic Series 757P Air Maintenance Trim Assembly
(AMTA) with Pressure Switch Option . . . . . . . . . . . . . . . . . . . . . 10
Shop Air or Tank-Mounted Air Compressors. . . . . . . . . . . . . . . . . . 11
Victaulic Series 757 Regulated Air Maintenance
Trim Assembly (AMTA) Option . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Compressor Requirements and Settings for
Series 769 FireLock NXT Preaction Valves
Installed with Series 746-LPA Dry Accelerators . . . . . . . . . . . . . 11
Settings for Air Supervisory Pressure Switches
and Alarm Pressure Switches . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Remote System Test Valve Requirements. . . . . . . . . . . . . . . . . . . . 11
Important Installation Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Valve/TrimInstallation ....................................12
Compression Fitting and Tube Installation . . . . . . . . . . . . . . . . . . . 12
HydrostaticTesting ......................................12
System Sensor PDRP-2001 Field Wiring Diagram (Standard). . . . . . . 14
System Sensor PDRP-2001 Field Wiring Diagram
(Standard, Low-Pressure Switch - Double-Interlocked,
Electric-Pneumatic/Electric) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Potter PFC-4410RC Field Wiring Diagram (Standard). . . . . . . . . . . . . 16
Potter PFC-4410RC Field Wiring Diagram
(Standard, Low-Pressure Switch - Double-Interlocked,
Electric-Pneumatic/Electric) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Sample Program for System Sensor PDRP-2001 Panel . . . . . . . . . . . 18
Sample Program for Potter Signal PFC-4410RC Panel . . . . . . . . . . . . 19
Placing the System in Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
ExternalInspection ......................................26
WeeklyInspection.....................................26
MonthlyInspection ....................................26
RequiredTests..........................................27
MainDrainTest.......................................27
WaterFlowAlarmTest..................................28
AutoConvertSystemTest................................29
Water Level and Low Air Alarm Tests . . . . . . . . . . . . . . . . . . . . . . . 32
Required Operational (Trip) Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Partial Operational (Trip) Test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Full Operational (Trip) Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Required Internal Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Maintenance...........................................41
Removing and Replacing the Clapper Seal. . . . . . . . . . . . . . . . . . . 41
Removing and Replacing the Clapper Assembly. . . . . . . . . . . . . . . 43
Installing the Cover Plate Gasket and Cover Plate. . . . . . . . . . . . . . 45
Removing and Replacing the Diaphragm Assembly . . . . . . . . . . . . 46
Replacing the Strainer Screen for Series 776
Low-PressureActuators...............................47
Troubleshooting – Series 776 Low-Pressure Actuator . . . . . . . . . . . . . 48
Troubleshooting – Series 746-LPA Dry Accelerator. . . . . . . . . . . . . . . 48
Troubleshooting – Series 753-E Solenoid Valve . . . . . . . . . . . . . . . . . 48
Troubleshooting – AutoConvert Trim Assembly. . . . . . . . . . . . . . . . . . 48
Troubleshooting–System .................................49
HAZARD IDENTIFICATION
Definitions for identifying the various hazard levels are
provided below. When you see this symbol, be alert to the
possibility of personal injury. Carefully read and fully
understand the message that follows.
WARNING
• Theuseoftheword“WARNING”identifiesthepresence
ofhazardsorunsafepracticesthatcouldresultindeathor
seriouspersonalinjuryifinstructions,includingrecommended
precautions,arenotfollowed.
CAUTION
• Theuseoftheword“CAUTION”identifiespossiblehazardsor
unsafepracticesthatcouldresultinpersonalinjuryandprod-
uctorpropertydamageifinstructions,includingrecommended
precautions,arenotfollowed.
NOTICE
• Theuseoftheword“NOTICE”identifiesspecialinstructions
thatareimportantbutnotrelatedtohazards.
REV_B
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELEC
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
I-769P.AC/ELEC_1

INSTALLER SAFETY INSTRUCTIONS
WARNING
• Anexperienced,trainedinstallermustinstall
thisproductinaccordancewithallinstruc-
tions.Theseinstructionscontainimportant
information.
• Depressurizeanddrainthepipingsystem
beforeattemptingtoinstall,remove,adjust,
ormaintainanyVictaulicpipingproducts.
Failuretofollowtheseinstructionscancause
productfailure,resultinginseriouspersonal
injuryand/orpropertydamage.
GENERAL
1. Readandunderstandallinstructionsandrefertothetrim
diagramsbeforeproceedingwiththeinstallation,maintenance,
andtestingofthisVictaulicSeries769FireLockNXTPreaction
ValvewithAutoConverttrim.
2. Inspecttheshipment. Make sure all components are included in
the shipment and that all necessary tools are available for installa-
tion.
3. Useonlyrecommendedaccessories. Accessories and equipment
that are not approved for use with this valve may cause improper
system operation.
4. Wearsafetyglasses,hardhat,footprotection,andhearing
protection. Wear hearing protection if you are exposed to long
periods of noisy job-site operations.
5. Preventbackinjury. Larger and pre-trimmed valves are heavy and
require more than one person or mechanical lifting equipment to
position and install the assembly. Always practice proper lifting
techniques.
6. Avoidusingelectricallypoweredtoolsindangerousenviron-
ments. When using electrically powered tools for installation, make
sure the area is moisture-free. Keep the work area well lit, and
allow enough space to accommodate proper installation of the
valve, trim, and accessories.
7. Watchforpinchpoints. Do not place fingers under the valve
body where they could be pinched by the weight of the valve. Use
caution around spring-loaded components (i.e. clapper assembly).
8. Keepworkareasclean. Cluttered areas, benches, and slippery
floors can create hazardous working conditions.
9. PROTECTTHESYSTEMFROMFREEZINGCONDITIONS.THE
VALVEANDSUPPLYPIPINGMUSTBEPROTECTEDFROM
FREEZINGTEMPERATURESANDMECHANICALDAMAGE.
10. IFTHEINLETWATERSUPPLYISINTERRUPTEDFORANY
REASON,ANDSYSTEMSUPPLYPRESSURETOTHEVALVE
DECREASES,MAKESURETHEDIAPHRAGMCHARGELINEIS
FULLYPRESSURIZEDBEFOREPLACINGTHESYSTEMBACK
INSERVICE.
MAINTENANCEANDTESTING
1. Notifytheauthorityhavingjurisdiction. Always notify the author-
ity having jurisdiction before performing any maintenance that
eliminates the fire protection provided by the system.
2. FollowNFPArequirementsforsystemtestingandinspection
schedules. The building owner or their representative is responsi-
ble for inspecting the system in accordance with current NFPA-25
requirements or in accordance with the requirements of the local
authority having jurisdiction (whichever is more stringent).
3. Depressurizeanddrainthesystemcompletelybeforeperforming
anymaintenance. Water under pressure can cause the cover plate
to blow off during removal if the system is not depressurized and
drained completely.
4. Protectthevalvefromfreezingtemperatures,foreignmatter,
andcorrosiveatmospheres. Any condition that might degrade the
system or affect system performance must be avoided.
INTRODUCTION
The following instructions are a guide for proper installation of Victaulic
Series 769 FireLock NXT Preaction Valves with AutoConvert Trim. These
instructions involve pipe that is properly prepared and grooved in accor-
dance with current Victaulic specifications.
NOTICE
• Drawingsand/orpicturesinthismanualmaybeexaggeratedfor
clarity.
• Thisproductandthisinstallation,maintenance,andtesting
manualcontaintrademarks,copyrights,and/orpatentedfeatures
thataretheexclusivepropertyofVictaulic.
I-769P.AC/ELEC_2
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELEC
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
REV_B

TRIMDIMENSIONS
THEGRAPHICSHOWNBELOWISREPRESENTATIVEOFTHE1–2-INCH/48.3–60.3-MMTRIMCONFIGURATIONS.
THEGRAPHICSHOWNBELOWISREPRESENTATIVEOFTHE2–8-INCH/73.0–219.1-MMTRIMCONFIGURATIONS.
A
J
*A1
B
*B1
G
F
D*D1
C
Full Open
K
*E1
H
E
Size Dimensions–inches/mm
Aprx.WeightEa.
lbs/kg
Nominal
Size
inches
mm
Actual
Out.Dia.
inches
mm AA1* B B1* C D D1* EE1 FG* H J K
Without
Trim
With
Trim
1½
40
1.900
48.3
9.00
228.60
16.43
417.32
36.50
927
46.75
1187
10.75
273
14.75
375
16.75
425
12.00
304.8
8.50
216
11.75
298
29.75
756
3.04
77.21
9.17
232.91
6.98
177.29
16.7
7.6
43.0
19.5
2
50
2.375
60.3
9.00
228.60
16.43
417.32
36.50
927
46.75
1187
10.75
273
14.75
375
16.75
425
12.00
304.8
8.50
216
11.75
298
29.75
756
3.04
77.21
9.17
232.91
6.98
177.29
17.0
7.7
43.0
19.5
2 ½
65
2.875
73.0
12.61
320.29
16.50
419.10
41.50
1054
51.50
1308
11.50
292
16.00
406
18.50
470
11.75
298.5
9.00
229
11.50
292
28.00
711
3.90
99.06
10.50
266.70
6.93
176.02
41.0
18.7
65.0
29.5
76.1 mm 3.000
76.1
12.61
320.29
16.50
419.10
41.50
1054
51.50
1308
11.50
292
16.00
406
18.50
470
11.75
298.5
9.00
229
11.50
292
28.00
711
3.90
99.06
10.50
266.70
6.93
176.02
41.0
18.7
65.0
29.5
3
80
3.500
88.9
12.61
320.29
16.50
419.10
41.50
1054
51.50
1308
11.50
292
16.00
406
18.50
470
11.75
298.5
9.00
229
11.50
292
28.00
711
3.90
99.06
10.50
266.70
6.93
176.02
41.0
18.7
65.0
29.5
4
100
4.500
114.3
15.03
381.76
19.78
502.41
42.25
1073
52.50
1334
13.25
337
18.25
464
21.50
546
12.00
304.8
9.00
229
13.50
343
27.75
705
6.25
158.75
9.62
244.34
8.46
214.88
59.0
26.7
95.0
43.0
165.1 mm 6.500
165.1
16.00
406.40
22.00
558.80
42.50
1080
52.75
1340
13.75
349
19.25
489
23.75
603
12.00
304.8
8.50
216
13.75
349
27.00
686
6.20
157.48
9.62
244.34
8.84
224.53
80.0
36.2
116.0
52.6
6
150
6.625
168.3
16.00
406.40
22.00
558.80
42.50
1080
52.75
1340
13.75
349
19.25
489
23.75
603
12.00
304.8
8.50
216
13.75
349
27.00
686
6.20
157.48
9.62
244.34
8.84
224.53
80.0
36.2
116.0
52.6
8
200
8.625
219.1
17.50
444.50
22.94
582.67
42.25
1073
52.25
1327
15.25
387
22.00
559
27.00
686
12.75
323.9
8.75
222
14.75
375
25.50
648
6.05
153.67
9.40
238.76
10.21
259.33
122.0
55.3
158.0
71.6
NOTES: Components shown as dotted lines denote optional equipment
* Measurements denoted with an asterisk take optional equipment into account
Optional drain connection kit is shown for reference and takeout dimensions.
The 1 ½ – 2-inch/48.3 – 60.3-mm configurations contain ¾-inch/19-mm drain valves. The 2½ – 3-inch/73.0 – 88.9-mm configurations contain
1 ¼-inch/31-mm drain valves. The 4 – 8-inch/114.3 – 219.1-mm configurations contain 2-inch/50-mm drain valves.
REV_B
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELEC
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
I-769P.AC/ELEC_3

EXPLODEDVIEWDRAWING–TRIMCOMPONENTS
SERIES769FIRELOCKNXTPREACTIONVALVE–ELECTRICAUTOCONVERTDRYTRIM
(OPTIONALACCESSORIESALSOSHOWN)
From Water
Supply
2
3
1
18
20
19
14
17
19
15
16
10
21
Standard
Conguration
Assembly (See
Exploded View on
Opposite Page)
AutoConvert Trim
Assembly (See Exploded
View on Opposite Page)
22
To System
24
Note 1
Bill of Materials
1 Series 769 FireLock NXT Preaction Valve
2FireLock Rigid Coupling (Optional/Sold
Separately – Comes Standard when VQR
Assembly is Ordered)
3Water Supply Main Control Valve
(Optional/Sold Separately – Comes
Standard when VQR Assembly is Ordered)
4Drain Swing Check Valve
5Drip Cup with Cap
6Alarm Pressure Switch (Optional/Sold
Separately – Comes Standard when VQR
Assembly is Ordered)
7Series 729 Drip Check Valve
8Diaphragm-Charge-Line Ball Valve
(Normally Open)
93-in-1 Strainer/Check/Restrictor
Assembly
10 Series 760 Water Motor Alarm
(Optional/Sold Separately)
11 Alarm Test Ball Valve
12 Diaphragm-Charge-Line Pressure
Gauge (0-300 psi/0-2068 kPa/0-20.7 Bar)
13 Series 749 Auto Drain
14 Air Supervisory Pressure Switch
(Optional/Sold Separately – Comes
Standard when VQR Assembly is Ordered)
15 System Pressure Gauge
(0-80 psi/0-552 kPa/0-5.5 Bar with Retard)
16 Water Supply Main Drain Valve - Flow Test
17 Water Supply Pressure Gauge
(0-300 psi/0-2068 kPa/0-20.7 Bar)
18 Drain Connection Kit (Optional/Sold
Separately – Comes Standard when VQR
Assembly is Ordered)
19 Gauge Valve
20 System Main Drain Valve
21 Series 755 Manual Pull Station
22 Series 748 Ball Check Valve
23 Series 746-LPA Dry Accelerator
(Optional/Sold Separately)
24 Series 753-E Solenoid Valve
25 Latching Solenoid Assembly
26 Braided Stainless Steel Flex Hose
27 Series 776 Low-Pressure Actuator
28 AutoConvert Assembly Air Pressure Gauge
(0-80 psi/0-5.5 Bar with Retard)
29 Strainer
30 AutoConvert Assembly Pre-Set Air
Pressure Switch
NOTE 1: Connection point for the Series 75D Water Column Device Kit
For information regarding installation of the Series 75B Supplemental Alarm Device or the Series 7C7 Air Maintenance/Compressor Assembly (not shown), refer
to the instructions supplied with the product..
I-769P.AC/ELEC_4
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELEC
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
REV_B

30
To AutoConvert
Trim Assembly
To Series 753-E
Solenoid Valve
To Diaphragm
Housing
From Water
Supply
From
Diaphragm
Housing
To Drain Connection
Assembly or Drain
Remove this plug when
installing an optional
pressure switch.
Remove this
plug when
installing an
optional water
motor alarm.
To Lower Port of
Water Supply
Main Drain Valve
From Alarm Port
of Preaction
Valve Body
When a supplemental
alarm device is
required, remove
plug and attach alarm
feed here
When installing a
Manual Pull Station,
remove plug and
connect to tting
To Drip Cup
Location

or Drain
Location

To Drip Cup
Location

or Drain
Exploded View of AutoConvert
Trim Assembly
To System Main
Drain Valve
From System
Air Feed
The exible hose can be
re-oriented, as required, by
rotating the ½-inch NPT tee 90°
From Series 753-E
Solenoid Valve
When installing an optional Dry
Accelerator, re-locate the gauge, as
indicated. Replace the ¼-inch NPT close
nipple with a ¼-inch NPT x 2-inch nipple
to ensure clearance between the gauge
and ball valve.
26
To Drip Cup
Location

or Drain
28
29
23
9
25
27
19
11
13
6
12
8
4
7
9
5
Exploded View of Standard
Conguration Assembly
REV_B
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELEC
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
I-769P.AC/ELEC_5

EXPLODEDVIEWDRAWING–INTERNALVALVECOMPONENTS
Clapper
Seal
Diaphragm
Assembly
Latch
Clapper
Seat
NOTE: VALVE IS SHOWN ABOVE IN THE “SET” POSITION
Exaggerated for Clarity
Bill of Materi
1
12
11
17
17
11
21
20
9
4
3
10
18
19
7
8
15
16
14
13
2
5
6
als
1 Valve Body 12 Cover Plate
2Clapper 13 Cover Plate Gasket
3Clapper Seal 14 Cover Plate Bolts*
4Seal Ring 15 Latch
5Seal Washer 16 Latch Spring
6Seal Retaining Ring 17 Latch Shaft Bushing and O-Ring (Qty. 2)
7Seal Assembly Bolt 18 Diaphragm
8Bolt Seal 19 Diaphragm Cover
9Clapper Spring 20 Diaphragm Cover Cap Screws (Qty. 8)
10 Clapper Shaft 21 Latch Shaft
11 Clapper Shaft Bushing and O-Ring (Qty. 2)
* NOTE: The 1½-inch/48.3-mm and 2-inch/60.3-mm valve sizes contain washers under the heads of
the cover plate bolts.
I-769P.AC/ELEC_6
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELEC
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
REV_B

DESCRIPTION–AUTOCONVERTTRIMASSEMBLY
The AutoConvert Trim Assembly consists of a latching solenoid mod-
ule and a Series 776 Low-Pressure Actuator. The AutoConvert Trim
Assembly monitors incoming power to the Fire Alarm Control Panel
(FACP) and allows for continuous fire protection in the event of an AC
power loss, without draining battery backup.
In the event of an AC power loss, the latching solenoid module receives
a quick electrical pulse from the FACP to latch open. The latching sole-
noid module stays in the open position without requiring additional cur-
rent draw. This allows the FACP to continuously monitor the system and
provide alarms in the event of a fire condition for the normal life of the
battery backup or until power is restored.
In the open condition, air is allowed to flow through the latching sole-
noid module to the Series 776 Low-Pressure Actuator and converts the
system to a non-interlocked condition. An air loss in the system piping
or an electrical release from the FACP would allow the preaction valve to
actuate and fill the sprinkler system piping with water.
The system continues to act as a dry valve until AC power is restored.
When AC power is restored, the latching solenoid module receives
another quick electrical pulse from the FACP to latch closed. The preac-
tion system then returns to its standard release method. Manual reset-
ting of the system is not required.
1
6
2
5
7
8
3
4
9
Bill of Materials
1Braided Stainless Steel Flex Hose
2Latching Solenoid Module
3 AutoConvert Assembly Air Pressure Gauge
(0-80 psi/0-5.5 Bar with Retard)
4Gauge Valve
5Series 776 Low-Pressure Actuator
63-in-1 Strainer/Check/Restrictor Assembly
7Strainer
8Restrictor
9AutoConvert Assembly Pre-Set Air Pressure Switch
LATCHINGSOLENOIDMODULECUTAWAY
Enclosure
Washer
Nut
Stando Panel
Support
Screw
Self-Sealing
Lock Washer
Lock Nut
Latching
Solenoid
O-Ring
Stando
REV_B
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELEC
INSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
I-769P.AC/ELEC_7

SECTIONVIEWDRAWINGANDDESCRIPTION–
SERIES776LOW-PRESSUREACTUATOR
The Series 776 Low-Pressure Actuator is located in the trim of Series
769 FireLock NXT Preaction Valves and acts as the trigger for these
systems.
Diaphragms separate the low-pressure actuator into three chambers.
The upper air chamber controls activation, while the middle and lower
chambers act as the water valve.
During setup, system air is applied to the upper chamber of the low-
pressure actuator. When the Auto Vent Sleeve of the low-pressure
actuator is pulled up, the upper chamber manually sets. Air pressure in
the upper chamber holds the Auto Vent closed, while it exerts force on
the water seal of the middle chamber.
When the diaphragm charge line is opened, water enters the lower
chamber of the low-pressure actuator. Water that enters the low-
pressure actuator flows to the middle chamber through the inlet eyelet,
which is pressurized by system air pressure in the upper chamber.
Since the area of the lower diaphragm (exposed to water pressure in
the middle chamber) is greater than the area of the lower chamber, the
lower chamber seals off. Water does not flow to the outlet of the low-
pressure actuator, and the supply water pressure creates the water seal.
When system air pressure decays to 7 psi/0.5 Bar, the force exerted
by the compression spring in the Auto Vent is greater than the force
exerted by air in the upper chamber. The Auto Vent opens, and all air
pressure in the upper chamber evacuates.
The upper diaphragm releases water pressure in the middle chamber
of the low-pressure actuator, which allows the lower diaphragm to lift
and water to flow from the inlet to the outlet. This flow of water releases
pressure from the diaphragm charge line of the Series 769 FireLock
NXT Preaction Valve, thus allowing the diaphragm to retract. The
clapper opens, and water flows into the sprinkler system.
VENT TO ATMOSPHERE
INLET
AIR IN
OUTLET
Illustration is exaggerated for clarity
* Denotes components that can be replaced in the field
Auto Vent Sleeve
Auto Vent Screw
Auto Vent Assembly*
Upper Chamber
Upper Diaphragm Wave Spring
Lower Diaphragm Wave Spring
Outlet Eyelet
Lower Chamber
Lower Diaphragm Assembly
Strainer Screen*
Strainer O-Ring Seal*
Strainer Assembly
Inlet Eyelet
Middle Chamber
Upper Diaphragm Assembly
I-769P.AC/ELEC_8
FireLockNXT™AutoConvertPreactionValve
SERIES 769
PreactionElectricAutoConvertDryTrim
I-769P.AC/ELECINSTALLATION,MAINTENANCE,ANDTESTINGMANUAL
www.victaulic.com
VICTAULIC IS A REGISTERED TRADEMARK OF VICTAULIC COMPANY. © 2009 VICTAULIC COMPANY. ALL RIGHTS RESERVED. PRINTED IN THE USA.
REV_B