Series-AT-A3000Configuration

Supported Applications

The Dwyer Series AT-A3000 ATEX/IECEx Photohelic® Pressure Switch/Gage is a versatile, highly repeatable instrument designed to measure and control positive, negative, or differential pressures of air and non-combustible, compatible gases. This 2-in-1 device combines the time-proven Magnehelic® gage design with low/high pressure switches for continuous monitoring and limit control in hazardous areas.

Documented applications include:

• Fan and damper control systems
• Hazardous area environments requiring ATEX or IECEx certification
• Processes involving air and non-combustible, compatible gases

Operating Conditions & Performance

The Series AT-A3000 operates within an ambient temperature range of 20 to 120°F (-6.67 to 48.9°C), with a low-temperature option available down to -28.8°C (-20°F). The instrument features flameproof aluminum enclosures rated IP66 (IP65 for versions VS1, VS2, VL1) and is approved under ATEX Certificate INERIS 21ATEX0033X and IECEx Certificate IECEx INE 21.0064X.

Performance specifications include:

• Accuracy: ±2% of full scale at 70°F (21.1°C); ±3% on -0 and +0 models; ±4% on -00 models
• Repeatability: ±1% of full scale
• Hysteresis/Deadband: One pointer width, less than 1% of full scale (variable dead band available via interlocked set points)
• Response Time: Increased response time at low pressures with LD port configuration; long runs will increase response time slightly
• Pressure Limits: Ranges from -20" Hg. to 25 psig (-0.677 to 1.72 bar) up to specific high-pressure options (MP: 35 psig, HP: 80 psig); model-specific limits apply for VS/VL port configurations

Measurement Ranges and Pressure Limits

The series supports a wide range of differential pressure measurements in inches water column (w.c.), including:

• A3001: 0 to 1.0 w.c.
• A3002 through A3005: 0 to 2.0, 3.0, 4.0, and 5.0 w.c.
• A3006 through A3010: 0 to 6.0, 8.0, and 10 w.c.
• Extended ranges up to A3150 (0 to 150 w.c.)

Pressure limits for port/valve configurations vary by model: VS0/VL0 support 10 kPa; VS1/VL1 support 20 kPa (one port) or 15 kPa (both ports); VS2 supports up to 40 kPa.

Electrical and Environmental Ratings

• Power Supply: 120 VAC, 50/60 Hz; 240 VAC & 24 VAC optional
• Switch Output: Each setpoint has 2 Form C relays (DPDT), rated at 10A @ 28 VDC or 10A @ 120/240 VAC
• Housing Material: Aluminum with glass window option for viewing set points and process pressure
• Certifications: ATEX: II 2D Ex tb IIIC T75°C Db; IECEx: Ex db IIC T5, T6 Gb (-60°C≤Tas≤+50°C) or Ex tb IIIC T75°C Db
• Weight: Approximately 19.8 lb (9 kg)

Configuration Options

The Series AT-A3000 is configurable across multiple parameters to meet specific installation and operational needs.

Housing and Enclosure Options

• Enclosures: Flameproof aluminum with glass window (standard) or blind cover option
• Cover Types: Glass window for visibility; Blind cover for protection without viewing access
• Housing Material Codes: 102PA indicates Aluminum enclosure

Sensor and Range Selection

• Ranges: Configurable via model suffix (e.g., A3001 to A3150) covering 0–1.0 w.c. up to 0–150 w.c.
• Accuracy Classes: Standard (-2%), -0/+0 models (±3%), and -00 models (±4%)
• Temperature Options: Standard construction or low-temperature option down to -28.8°C (-20°F)

Port/Valve Configurations

• Materials: Brass (code 1) or Stainless Steel (SS, code 2)
• Configurations:
  • VS0: Standard port/no valve
  • VL0: Low-differential (LD) port/no valve
  • VS1/VS2/VL1: Various combinations of standard/LD ports and valves

Electrical Connections and Power

• Cable Entry: 1/2" NPT ANSI/ASME B1.20.1 (code 12)
• Terminals: Screw terminals; use 167°F (75°C) copper conductors only
• Power Options: 120 VAC, 240 VAC, or 24 VAC

Special Features and Accessories

• Silicon-free option (XSFX)
• Dwyer Part No. A-601 with palladium/gold contacts for manual reset
• Five-foot cable assembly for remote relays; longer lengths available from factory
• Filter vent plug or similar fitting for reference pressure tap (No. A-331)

Key Product Differences

The Series AT-A3000 is distinguished by its dual functionality as both a precision gage and a limit switch, with set points adjustable via face-mounted knobs accessible after de-energizing the instrument. Unlike standard switches, this series maintains continuous gage readings unaffected by relay operation or power loss.

Model Number Construction

The model number follows the format: AT - <ENCLOSURE> - <RANGE> - <POWER> - <OPTIONS> - <COVER> - <PORT/VALVE MATERIAL> - <CONFIGURATION> - <CABLE ENTRY>. Example: AT-102PA-A3001-120VAC-XSFX-W1VS012.

Housing and Viewing Options

• Glass Window (W): Allows viewing of set point needles and process pressure through the flameproof enclosure.
• Blind Cover (B): Provides protection without visual access to internal components.

Port/Valve Material Differences

• Brass: Standard wetted material for general service; consult factory for compatibility with specific gases.
• Stainless Steel (SS): Optional upgrade for enhanced corrosion resistance or specialized media requirements.

Temperature and Construction Variants

• Standard: Operates from 20 to 120°F (-6.67 to 48.9°C).
• Low-Temperature (XXLT): Extends lower limit to -28.8°C (-20°F) for cold environments.
• Silicon-Free (XSFX): Eliminates silicone compounds in construction where contamination is a concern.

Pressure Limit Behavior by Configuration

The maximum allowable pressure varies significantly based on port/valve selection. For example, VS0 and VL0 configurations support 10 kPa regardless of single or dual-port connection, while VS2 supports up to 40 kPa with one port connected but only 20 kPa when both ports are active.

Relay Interlocking Capability

The two Form C relays per set point can be interlocked to provide variable deadband control, enabling precise management of fan and damper operations without external logic circuits. This feature is unique to the Photohelic® design within this series.