Overview
The Mercoid M-51-71 is a proven bi-metal air temperature switch engineered for automatic temperature control in heating and cooling systems. Built for durability and precision, this model is widely used in commercial HVAC, industrial ovens, dryers, and furnaces where reliable temperature switching is critical. Its double-adjustable design and automatic reset capability make it an ideal drop-in replacement for existing systems.
Key Features
- Bi-metal sensing element for accurate temperature detection
- Double-adjustable set point and reset point with visible dial indication
- Automatic reset on temperature drop for hands-free operation
- Compact mounting flange, reversible for flat or curved duct surfaces
- Screw terminal electrical connections for simple integration
- UL listed and CSA certified for industrial compliance
Technical Specifications
- Temperature Range: 25 to 125°F (-4 to 52°C)
- Deadband: 5⁄8 inches (136 mm) insertion length
- Switch Action: Opens on temperature rise with automatic reset
- Electrical Rating: 3⁄4 HP @ 120/240 VAC single phase; 1⁄3 HP @ 120/240 VDC
- Electrical Connections: Screw terminal
- Process Connection: 7⁄8 inch (22.2 mm) conduit opening; 1⁄2 inch (12.7 mm) conduit hub
- Mounting: Horizontal and level orientation required
- Switch Type: SPDT or DPST available
- Weight: 5 lb (2.27 kg)
- Agency Approvals: UL, CSA
- Scale Indication: °F standard; °C optional
Typical Applications
- HVAC duct temperature monitoring and fan control
- Furnace limit switch and alarm applications
- Industrial bake ovens and drying equipment
- Damper control systems for fire safety and thermal regulation
- Refrigeration system support and cooling cycle control
Compatibility & Replacements
Compatible With
- Standard 120/240 VAC single-phase circuits
- Standard 120/240 VDC control circuits
- Screw terminal connection systems and conduit hubs
- HVAC control panels and furnace limit switch stations
- Industrial process control and damper activation systems
Replaces / Drop-In Replacement For
- Original equipment Mercoid M-51-71 units
- Verify compatibility with your system integrator before ordering
Works With
- Standard AC/DC relay logic and control circuits
- Pneumatic and electric damper control systems
- HVAC fan control relays and interlocks
- Fire and smoke detection damper systems
- Screw terminal and conduit connection standards
