CA-FIRE Protection · Fujian, China
Dry Alarm Valve — ZSFC Series with Accelerator
DN100–DN200 · 1.6 MPa · Pneumatic Accelerator · Freeze-Rated to −20°C · GB 5135.2 · NFPA 13
ZSFC Series · Pneumatic Accelerator · GB 5135.2 · NFPA 13
Dry Alarm Valve — ZSFC Series with Accelerator
DN100–DN200 · 1.6 MPa
A dry alarm valve is the control component in a dry-pipe automatic fire sprinkler system — designed for environments where standing water in the distribution pipework would freeze and disable the system. Instead of water, the downstream pipework is charged with compressed air or dry nitrogen at supervisory pressure (0.14–0.28 MPa). Water is held back at the dry alarm valve body. When a sprinkler head opens in a fire, the downstream air pressure drops, the differential clapper trips, and water floods the system to discharge through the open head.
CA-FIRE's ZSFC series dry alarm valve is available in DN100, DN150, and DN200 with flanged connections, rated to 1.6 MPa working pressure, and compliant with GB 5135.2 and NFPA 13. A pneumatic accelerator is matched to all three sizes — reducing water delivery time to under 60 seconds, meeting NFPA 13's mandatory trip time requirement.
The ZSFC is the correct specification for cold storage, unheated warehouses, parking garages, loading dock canopies, and roof spaces. For environments where both freeze protection and false-discharge prevention are required simultaneously, see the pre-action alarm valve. For standard heated buildings, see the wet alarm valve ZSFZ. ← See all alarm check valve types
Quick Specifications
ModelZSFC 100 / 150 / 200
ConnectionFlanged (GB / ANSI / DIN)
SizesDN100 · DN150 · DN200
Working Pressure1.6 MPa (16 bar)
Seal Test3.2 MPa
Strength Test6.4 MPa
Supervisory Air0.14–0.28 MPa (20–40 psi)
Air-to-Water Ratio≈ 1:6 (differential clapper)
Water Delivery<60 s (with accelerator)
Body MaterialDuctile cast iron, epoxy coated
Clapper FacingEPDM rubber
System Side Temp.To −20°C
Valve Room Temp.Must remain ≥ 4°C
StandardGB 5135.2 · NFPA 13 · ISO 9001
Key Features
Freeze-Rated to −20°C — No Water in Distribution Pipework
The entire downstream distribution network contains only compressed air or dry nitrogen in standby — no water that can freeze. The ZSFC valve body and all water-side components are installed inside a heated enclosure (≥4°C). Only the air-charged distribution pipework extends into the cold zone, rated to operate in ambient temperatures down to −20°C without system impairment.
Pneumatic Accelerator — Water Delivery <60 s, NFPA 13 Compliant
Without an accelerator, a dry pipe system must vent all downstream air through the open sprinkler before the clapper trips — 90+ seconds on practical system sizes. The pneumatic accelerator detects the initial pressure drop and immediately vents the differential chamber, tripping the clapper before full air evacuation. Water delivery time drops below the mandatory NFPA 13 60-second limit.
1:6 Differential Clapper — Low Air Pressure Holds Full Water Supply
The ZSFC uses a differential pressure clapper — the effective area exposed to system air pressure is larger than the seat area exposed to water supply pressure, at approximately a 6:1 ratio. This allows 0.14–0.28 MPa supervisory air to reliably hold back the full 1.6 MPa water supply pressure without requiring high-pressure air equipment.
Low-Air Alarm Switch — Early Warning Before System Trip
A low-air pressure alarm switch monitors supervisory pressure continuously. If air pressure drops below the minimum setpoint — indicating a distribution system leak or compressor fault — it sends an electrical signal to the fire alarm panel before the dry alarm valve trips. This allows maintenance teams to investigate and repair leaks before an unwanted system activation.
Dimensional Data — 3 Sizes
| DN Size | Body Height (mm) | Working Pressure | Seal Test | Strength Test | Control Method |
|---|---|---|---|---|---|
| DN100 | 375 | 1.6 MPa | 3.2 MPa | 6.4 MPa | Pneumatic accelerator |
| DN150 | 455 | 1.6 MPa | 3.2 MPa | 6.4 MPa | Pneumatic accelerator |
| DN200 | 610 | 1.6 MPa | 3.2 MPa | 6.4 MPa | Pneumatic accelerator |
Operating Principle
How a Dry Alarm Valve Works — Step by Step
1
Pressurised Standby
Supply side (water) is pressurised at 1.6 MPa. System side (distribution pipework) is charged with compressed air at 0.14–0.28 MPa. Differential clapper is held shut — low air pressure on the larger clapper face balances the higher water pressure on the smaller seat face. Air pressure maintenance device compensates for minor leakage automatically.
2
Head Opens — Air Drops
A heat-activated sprinkler head opens. Compressed air begins venting through the open orifice. Air pressure on the system side starts to fall. The pneumatic accelerator detects the initial pressure drop within seconds — it does not wait for full air evacuation.
3
Accelerator Trips Clapper
The accelerator rapidly vents the intermediate chamber between the clapper's air face and water face. This destroys the differential pressure balance, causing the clapper to trip open immediately — before the full air volume in the distribution pipework has vented. This is the critical step that achieves <60 s water delivery time.
4
Water Floods System
Water enters the distribution pipework from the supply main, pushing the remaining air ahead of it through the open sprinkler head(s). The alarm port opens simultaneously — water drives the water motor alarm gong and pressurises the alarm pressure switch, sending an electrical signal to the fire alarm panel.
5
Water Reaches Open Head
Water reaches the open sprinkler head and begins suppression discharge. Total elapsed time from head opening to water discharge: <60 seconds with accelerator installed. Without accelerator: 90–180 seconds — non-compliant with NFPA 13.
6
Reset
Close supply isolation valve → open main drain valve → drain full system → manually reset clapper → replace activated sprinkler heads → recharge distribution pipework with dry compressed air or nitrogen to supervisory pressure → slowly reopen supply valve to return to standby.
Why the Accelerator is Not Optional: Without the accelerator, the dry alarm valve can only trip after the entire downstream air volume has vented through the open sprinkler orifice. On any practical system size this takes 90–180 seconds — far exceeding NFPA 13's mandatory 60-second maximum. The pneumatic accelerator reduces this to under 60 seconds on every activation — making the dry pipe system functionally comparable to a wet pipe system in suppression response speed.
Complete Dry Alarm Valve Station — Components
CA-FIRE supplies the ZSFC dry alarm valve as a valve body only or as a complete matched station assembly. Key difference from a wet alarm valve station: the dry system requires additional air-side components — accelerator, air pressure maintenance device, and low-air alarm switch — that have no equivalent in a wet pipe station.
| # | Component | Side | Function & Notes |
|---|---|---|---|
| 1 | ZSFC Dry Alarm Valve Body | Both | Differential pressure clapper; EPDM rubber facing; DN100/150/200; this product |
| 2 | Pneumatic Accelerator | Air side | Trips clapper on initial pressure drop; achieves <60 s water delivery; required for NFPA 13 compliance on all but the smallest systems |
| 3 | Air Pressure Maintenance Device | Air side | Automatically compensates for minor air leakage; maintains supervisory pressure without manual intervention; prevents spurious low-air alarms |
| 4 | Low-Air Alarm Pressure Switch | Air side | Signals fire alarm panel when supervisory pressure drops below minimum setpoint — early warning of system leak before valve trips; unique to dry pipe systems |
| 5 | System Air Pressure Gauge | Air side | Displays downstream supervisory air pressure; 0–0.5 MPa range; drop from setpoint indicates head activation or system leak |
| 6 | Supply Water Pressure Gauge | Water side | Displays upstream water supply pressure; 0–1.6 MPa range; monitored alongside air gauge in standby |
| 7 | Retard Chamber | Water side | Delays alarm signal 5–30 s; prevents false activations at gong and pressure switch from brief air pressure fluctuations |
| 8 | Water Motor Alarm Gong | Water side | Hydraulically driven mechanical bell; no electrical power; activates when valve trips; mandatory per GB 5135.2 |
| 9 | Alarm Pressure Switch | Water side | Electrical signal to fire alarm panel on valve trip; 24 V DC; zone identification for BMS and remote monitoring |
| 10 | OS&Y Gate Valve (upstream) | Water side | Supply isolation; tamper-switch supervised; locked open in normal operation |
| 11 | Main Drain & Inspector's Test Valve | Water side | Full-flow drain for post-activation reset and annual trip test; inspector's test connection for quarterly partial-flow alarm verification |
Dry vs Wet vs Pre-Action Alarm Valve — Selection Guide
The primary selection driver is whether the distribution pipework will be exposed to freezing temperatures, and whether accidental water discharge is a concern.
| Parameter | Dry Alarm Valve ZSFC (this product) | Wet Alarm Valve ZSFZ | Pre-Action Valve ZSFY |
|---|---|---|---|
| Downstream pipework | Compressed air / dry N₂ | Water (always charged) | Supervisory air |
| Freeze environments | ✓ Yes — to −20°C | ✗ No — pipe will freeze | ✓ Yes |
| Response speed | <60 s with accelerator | ✓ Immediate | Requires detector + head |
| False discharge protection | Low — any single head trips | Low — any single head trips | ✓ High — dual interlock |
| System complexity | Moderate — air system needed | ✓ Simplest | Most complex |
| Maintenance burden | Higher — air system monitoring | ✓ Lowest | Highest |
| Specify when | Freeze risk, no false-discharge concern | Indoor ≥4°C, standard building | Freeze risk + false discharge both critical |
Application Scenarios
🧊 Cold Storage & Blast-Freeze Warehouses
Operating at −18°C to −30°C — well below any wet-pipe threshold. Dry nitrogen preferred over compressed air to eliminate moisture and oxygen from the system side, preventing internal pipe corrosion. ZSFC with accelerator is standard specification for large-scale cold chain facilities. DN150–DN200 typical for high-rack cold store zones.
📦 Unheated Warehouses & Logistics Facilities
Large logistics warehouses typically include unheated sections — loading dock canopies, external transit areas, staging zones — exposed to sub-zero winter temperatures. The ZSFC dry alarm valve covers these zones, while the building's heated interior is served by ZSFZ wet alarm valves. Both systems operate independently from their respective riser stations.
🚗 Multi-Storey & Underground Parking Garages
Open-deck and partially enclosed parking structures in cold climates experience sub-zero ambient temperatures throughout winter. Dry pipe systems with ZSFC alarm valves protect these facilities without freeze-induced system failures. DN100 and DN150 cover typical parking structure zone flow demands.
🏭 Unheated Industrial Buildings
Manufacturing facilities, steel mills, and processing plants with unheated sections — particularly roof spaces above heated production areas — require dry pipe protection for exposed zones. The ZSFC DN100–DN200 range handles the full span of industrial sprinkler zone pipe sizes.
🏠 Building Roof Spaces & Attics
Where code requires sprinkler protection in unconditioned attic or roof void spaces, a dry pipe branch fed from a ZSFC alarm valve in the heated floor below provides freeze-protected coverage — without heating the roof space to wet-pipe operating temperatures.
🚚 Loading Docks & External Canopy Areas
Covered loading dock areas and external canopy structures attached to otherwise heated buildings. The ZSFC alarm valve station is located inside the heated building envelope; only the dry distribution pipework extends to the exposed canopy area, keeping all valve components above freezing while extending protection to the outdoor zone.
Standards & Certifications
| Standard | Scope & Relevance to ZSFC Dry Alarm Valve |
|---|---|
| GB 5135.2-2003 ↗ | 自动喷水灭火系统 第2部分 — Chinese national standard for dry alarm valves governing differential clapper design, seal test (3.2 MPa), strength test (6.4 MPa), trip time requirements, and accelerator performance. ZSFC series holds national fire product type approval certification under this standard. |
| NFPA 13 ↗ | Standard for the Installation of Sprinkler Systems — dry pipe system design requirements, mandatory 60-second water delivery time limit (accelerator required for compliance), supervisory air pressure range (0.14–0.28 MPa / 20–40 psi), and air supply requirements. CA-FIRE provides Cv data per DN size for NFPA 13 hydraulic calculations. |
| NFPA 25 ↗ | Standard for ITM of Water-Based Fire Protection Systems — dry pipe valve inspection schedule, quarterly partial trip test (accelerator trip test), annual full trip test, air maintenance device inspection, and low-air alarm switch function verification. |
| GB 50084 | 自动喷水灭火系统设计规范 — Chinese design code; specifies dry pipe system application conditions, valve room heating requirements (≥4°C), air supply equipment, and dry nitrogen vs compressed air selection guidance for cold-store applications. |
| ISO 9001:2015 ↗ | CA-FIRE QMS certification — covers casting inspection, differential clapper machining tolerances, EPDM material verification, accelerator calibration testing, full-system hydraulic pressure testing, and shipment documentation for all ZSFC sizes. |
Frequently Asked Questions
What is a dry alarm valve and when do I need one instead of a wet alarm valve?
A dry alarm valve controls a dry-pipe sprinkler system — one where the distribution pipework contains compressed air or nitrogen instead of water in standby. You need a dry alarm valve whenever the sprinkler distribution pipework will be exposed to temperatures below 4°C — the threshold at which standing water in pipes will freeze, rupture the pipe, and disable the system.
Typical applications requiring a dry alarm valve: cold storage facilities and blast-freeze warehouses (−18°C to −30°C); unheated loading dock canopies and staging areas; open-deck parking garages in cold climates; building roof spaces and attics without heating; and outdoor canopy areas. For any indoor area consistently maintained above 4°C, the simpler and faster-responding wet alarm valve is the correct choice.
Typical applications requiring a dry alarm valve: cold storage facilities and blast-freeze warehouses (−18°C to −30°C); unheated loading dock canopies and staging areas; open-deck parking garages in cold climates; building roof spaces and attics without heating; and outdoor canopy areas. For any indoor area consistently maintained above 4°C, the simpler and faster-responding wet alarm valve is the correct choice.
Is the pneumatic accelerator mandatory? What happens without it?
The pneumatic accelerator is effectively mandatory for any dry pipe system of practical size. Without it, the dry alarm valve can only trip after all the compressed air in the downstream distribution pipework has vented through the open sprinkler orifice. On a typical system this can take 90–180 seconds — well above the 60-second water delivery time limit mandated by NFPA 13.
With the pneumatic accelerator installed and calibrated correctly, the dry alarm valve trips within seconds of the initial air pressure drop — before the full air volume has vented. Water delivery time drops below 60 seconds on virtually all practical system sizes. CA-FIRE factory-calibrates and tests the accelerator matched to the ZSFC valve before shipment.
With the pneumatic accelerator installed and calibrated correctly, the dry alarm valve trips within seconds of the initial air pressure drop — before the full air volume has vented. Water delivery time drops below 60 seconds on virtually all practical system sizes. CA-FIRE factory-calibrates and tests the accelerator matched to the ZSFC valve before shipment.
Should I use compressed air or dry nitrogen in the distribution pipework?
Both work, but the choice matters for long-term pipe condition. Compressed air contains moisture and oxygen. In cold-store environments, moisture in the air supply can condense and freeze inside distribution pipework — blocking flow paths and causing premature internal pipe corrosion (microbiologically influenced corrosion / MIC). If using compressed air, an air dryer upstream of the distribution connection is strongly recommended.
Dry nitrogen from a cylinder supply eliminates both moisture and oxygen from the system side — dramatically reducing internal pipe corrosion and eliminating freeze risk from condensed moisture. For cold-store and blast-freeze applications, dry nitrogen is the preferred medium. The ZSFC valve body is compatible with both media — no modification required.
Dry nitrogen from a cylinder supply eliminates both moisture and oxygen from the system side — dramatically reducing internal pipe corrosion and eliminating freeze risk from condensed moisture. For cold-store and blast-freeze applications, dry nitrogen is the preferred medium. The ZSFC valve body is compatible with both media — no modification required.
What is the correct supervisory air pressure for the ZSFC dry alarm valve?
Set the supervisory air pressure at 0.14–0.28 MPa (20–40 psi). This range is specified by NFPA 13 and is the operating range within which the ZSFC differential clapper reliably holds back the full 1.6 MPa water supply pressure via the approximately 1:6 air-to-water pressure ratio.
The low-air alarm setpoint should be set approximately 0.007–0.014 MPa (1–2 psi) below the supervisory pressure setpoint. The accelerator trip point should be set approximately 0.014–0.028 MPa (2–4 psi) below the low-air alarm setpoint. This staggered sequence — supervisory pressure → low-air alarm → accelerator trip → valve trip — ensures the alarm panel receives early warning of a leak, and that the accelerator only trips on a genuine head activation. Do not set the supervisory pressure above 0.28 MPa; higher air pressure increases the trip pressure threshold of the accelerator and can slow response time.
The low-air alarm setpoint should be set approximately 0.007–0.014 MPa (1–2 psi) below the supervisory pressure setpoint. The accelerator trip point should be set approximately 0.014–0.028 MPa (2–4 psi) below the low-air alarm setpoint. This staggered sequence — supervisory pressure → low-air alarm → accelerator trip → valve trip — ensures the alarm panel receives early warning of a leak, and that the accelerator only trips on a genuine head activation. Do not set the supervisory pressure above 0.28 MPa; higher air pressure increases the trip pressure threshold of the accelerator and can slow response time.
What maintenance does the dry alarm valve require under NFPA 25?
Quarterly: Partial trip test — trip the accelerator using the inspector's test connection to verify accelerator function and alarm gong/pressure switch activation. Inspect air gauges for correct supervisory pressure. Check low-air alarm switch function. Visual inspection of valve body and trim for leaks. Verify air maintenance device is not running continuously (continuous operation indicates a significant system leak).
Annually: Full trip test — open the main drain valve and trip the full dry alarm valve to verify water delivery time is within the 60-second NFPA 13 requirement. Inspect retard chamber drain orifice. Verify OS&Y tamper switch function. Recharge system after test and verify accelerator reset correctly.
Every 5 years: Internal inspection — remove differential clapper and inspect seat, hinge, and EPDM facing for wear or deformation. Inspect accelerator internals. Replace EPDM components if compression set or cracking is observed. CA-FIRE supplies replacement clapper assemblies and accelerator service kits — contact [email protected].
Annually: Full trip test — open the main drain valve and trip the full dry alarm valve to verify water delivery time is within the 60-second NFPA 13 requirement. Inspect retard chamber drain orifice. Verify OS&Y tamper switch function. Recharge system after test and verify accelerator reset correctly.
Every 5 years: Internal inspection — remove differential clapper and inspect seat, hinge, and EPDM facing for wear or deformation. Inspect accelerator internals. Replace EPDM components if compression set or cracking is observed. CA-FIRE supplies replacement clapper assemblies and accelerator service kits — contact [email protected].
Can the ZSFC dry alarm valve be used on export projects specifying NFPA 13?
Yes — for most BRI, EPC, and ASEAN-region export projects specifying NFPA 13 compliance. The ZSFC series is designed in alignment with NFPA 13 functional requirements (60-second water delivery, 0.14–0.28 MPa supervisory pressure, accelerator compatibility) and holds Chinese national fire product type approval certification under GB 5135.2.
For projects with a contractual UL Listing or FM Approval requirement, contact [email protected] to discuss certification options. CA-FIRE provides full project submittal packages: Cv data per DN size, dimensional drawings in DWG/PDF, material certificates, accelerator calibration test records, and GB 5135.2 type approval certificates — all in English. Flange drilling available in ANSI B16.1, DIN 2501, and GB patterns.
For projects with a contractual UL Listing or FM Approval requirement, contact [email protected] to discuss certification options. CA-FIRE provides full project submittal packages: Cv data per DN size, dimensional drawings in DWG/PDF, material certificates, accelerator calibration test records, and GB 5135.2 type approval certificates — all in English. Flange drilling available in ANSI B16.1, DIN 2501, and GB patterns.
Related Products
Get a Quote — ZSFC Dry Alarm Valve
DN100 · DN150 · DN200 · 1.6 MPa · Pneumatic Accelerator · GB 5135.2 · NFPA 13 · ISO 9001
Valve body only or complete dry alarm valve station assembly · ANSI / DIN / GB flanges · Factory direct · 24 hr quote
📧 Send Inquiry →
Valve body only or complete dry alarm valve station assembly · ANSI / DIN / GB flanges · Factory direct · 24 hr quote