Overview
The Dwyer A3210 Photohelic pressure switch is a proven solid-state pressure measurement and switching device that merges analog gage indication with digital relay control. Engineered for HVAC, compressed air, and process pneumatic applications, this unit delivers reliable dual-relay switching with an uninterrupted visual pressure display—even during electrical power loss.
Key Features
- Photohelic sensing technology with infrared light shutter mechanism for chatter-free switching
- Dual DPDT (Form C) relays for independent high and low pressure setpoint control
- Front-mounted knob adjustment for easy setpoint and zero offset calibration
- Deadband less than 1% of full scale—individual setpoint width equals one pointer width
- Analog gage reading remains active independent of relay operation and power status
- Pressure range: 0–10 psi (standard 0–25 psi maximum; optional 35 psi or 80 psi ratings available)
Technical Specifications
- Service: Clean dry air, inert gases, non-combustible non-corrosive gases
- Accuracy: ±2% of full scale at 70°F (21.1°C)
- Pressure Limit: Standard 25 psig (1.7 bar); optional 35 or 80 psig available
- Switch Type: Two DPDT relays with latching or momentary options
- Repeatability: ±1% of full scale
- Temperature Operating Range: 20–120°F (–6.67–48.9°C); low-temperature option available
- Dial Face: 4 inches (101.6 mm)
- Dimensions: 5 inches O.D. × 8.25 inches depth
- Weight: 4 lbs (1.81 kg)
- Process Connection: 1/8 inch female NPT
Typical Applications
- HVAC filter clogging and static pressure monitoring
- Compressed air system high-low pressure alarms
- Pneumatic equipment pressure verification and control
- Furnace or ductwork differential pressure sensing
- Pump discharge and low-pressure cutoff protection
Compatibility & Replacements
Compatible With
- Standard 24 VAC/VDC control circuits with dry-contact relay inputs
- Pneumatic and low-pressure gas service systems
- HVAC building automation and monitoring panels
- Compressed air and industrial plant control systems
Replaces / Drop-In Replacement For
- Earlier Dwyer A3210 units with the same dial range and relay configuration
- Direct successor to non-solid-state Photohelic models in the same envelope
Works With
- Conventional relay-based control logic and PLC dry-contact inputs
- Building automation systems (BAS) supporting dry-contact switching
- Standard 1/8 inch NPT pneumatic tubing and hose adapters
- Low-temperature optional versions for cold storage and outdoor applications
