Rheem-Ruud 47-21900-01K Limit Switch

The Rheem-Ruud 47-21900-01K Limit Switch is a critical OEM replacement part designed for technicians managing residential and commercial heating cycles. This high-limit safety control features a 230°F cut-out temperature, engineered to provide positive circuit interruption in the event of an over-temperature condition within the flanged airstream. As a Manual Reset device, it ensures that your furnace or water heater remains offline for inspection if the safety threshold is breached, preventing recurrent cycling under unsafe parameters. This component utilizes an SPST (Single Pole Single Throw) electrical configuration, making it a direct cross-reference and upgraded replacement for the legacy 47-21900-01 part number. Built for durability in high-performance HVAC systems, it maintains tight calibration tolerances to prevent nuisance tripping while ensuring furnace high limit protection in demanding flanged mount applications.

Technical Performance & Benefits

• Direct OEM Compatibility: Specifically engineered for Rheem, Ruud, and WeatherKing equipment to ensure precise fit and HVAC safety switch reliability.
• Manual Reset Mechanism: Provides essential safety by requiring manual intervention after a 230-degree thermal event.
• SPST Contact Arrangement: Simplifies wiring and integration into existing control circuits for gas furnace limit switch replacement.
• Flanged Mounting: Designed for standardized airstream installation, optimizing thermal response time.
• Broad Application Range: Rated for use in both residential furnaces and commercial water heating equipment.

Common Technical Questions

What was the previous part number for this limit switch?
The 47-21900-01K is the current manufacturer-designated replacement for the 47-21900-01. It meets or exceeds the original specifications for the 230F CO M/R SPST configuration.

Why is a manual reset limit switch used instead of an automatic reset?
A manual reset limit switch is a safety requirement in specific furnace stages to ensure a technician identifies the cause of overheating—such as floor vent blockages or blower motor failure—before the system resumes operation.

Can this switch be used in flanged airstream applications?
Yes, its construction is specifically optimized for flanged airstream heating systems, ensuring the bimetal sensing element is correctly positioned to monitor heat exchanger temperatures.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.