In industrial automation and equipment safety, temperature control plays a critical role. Overheating not only reduces efficiency but can also lead to severe damage or safety incidents. The challenge lies in implementing reliable temperature monitoring and protection in a cost-effective manner. WIKA's TFS35 series temperature switch addresses this need with its compact design and robust functionality.

The TFS35 series is a bimetallic temperature switch designed for applications with switching voltages up to 48V. Its primary advantage lies in its self-sufficient operation—requiring no external power source—while providing current-independent switching action through bimetallic technology. This design simplifies installation and maintenance while enhancing reliability.

Common applications include temperature limitation and monitoring in mechanical systems, where it can shut down equipment or activate cooling fans when overheating occurs. Typical use cases span mobile hydraulic systems, machinery manufacturing, compressors, motors, and heating/cooling systems.

At the heart of the TFS35 lies its bimetallic strip—a composite of two metals with different thermal expansion coefficients. Temperature changes cause differential expansion, making the strip bend. When reaching the preset nominal switching temperature (NST), this triggers the switching action. Upon cooling to the reset switching temperature (RST), typically 15-30K below NST, the switch returns to its original state.

Unlike current-carrying bimetallic designs, the TFS35's strip carries no electrical current, eliminating self-heating effects that could cause false triggers. The built-in hysteresis prevents rapid cycling near threshold temperatures, extending operational life.

• Fixed switching temperature: Ensures precise control without adjustment errors
• Current-independent operation: Maintains consistent performance regardless of load variations
• Automatic reset: Returns to initial state when temperatures normalize, reducing maintenance
• Self-powered design: Eliminates need for auxiliary power supplies
• Compact installation: Simplified mounting and electrical connections

The switch offers two contact configurations:

• Normally Closed (NC): Opens circuit at threshold temperature—ideal for equipment shutdown
• Normally Open (NO): Closes circuit at threshold—suited for activating cooling systems or alarms

Key operational parameters include:

• Maximum switching voltage: 48V DC
• Switching current: Model-dependent (typically several amperes)
• NST options: Multiple fixed temperature settings available
• RST range: Typically 15-30K below NST
• Environmental rating: IP65 protection against dust and water ingress

Proper implementation ensures optimal performance:

• Mount at locations accurately reflecting monitored temperatures
• Secure mechanical connections via threaded or flange fittings
• Verify proper electrical terminations per wiring diagrams
• Conduct periodic inspections of connections and housing integrity
• Maintain cleanliness to preserve thermal responsiveness

Key considerations when specifying TFS35 models:

• Required NST range based on equipment operating parameters
• Contact configuration (NC/NO) matching control logic needs
• Voltage/current ratings compatible with control circuits
• Environmental protection level suited to installation conditions
• Mechanical connection type matching equipment interfaces

Compared to electronic alternatives, the TFS35 offers:

• Lower cost through mechanical simplicity
• Higher reliability without power supply dependencies
• Simpler installation without programming requirements
• Broad applicability across industrial environments

Limitations include fixed temperature settings and lower precision compared to electronic sensors—tradeoffs that suit many industrial protection scenarios.

Proven implementations include:

• Mobile hydraulic systems: Preventing oil overheating
• Motor protection: Safeguarding windings from burnout
• Compressor control: Managing operating temperatures

Industry trends point toward:

• Smart switches with digital interfaces
• Integrated multifunction devices
• Wireless monitoring capabilities
• Self-diagnostic features

The TFS35 represents a robust, economical solution for industrial temperature protection. Its mechanical reliability and straightforward implementation make it particularly valuable in cost-sensitive applications where dependable overheating protection remains paramount.