Rheem-Ruud 47-21711-10 Limit Switch

The Rheem-Ruud 47-21711-10 Limit Switch is a critical safety component designed for precise thermal regulation within HVAC systems. This board mounted general purpose limit switch features a Single Pole Single Throw (SPST) normally closed configuration, engineered to interrupt the heating circuit when temperatures exceed safe operating parameters. With a fixed open temperature of 170 degrees F and a fixed close temperature of 150 degrees F, it ensures reliable automatic reset functionality, eliminating the need for manual intervention after a thermal excursion. The 7-inch insertion length allows for accurate sensing deep within the heat exchanger airflow, making it a standard OEM replacement part for numerous gas furnace models. For technicians troubleshooting high-limit trips or airflow restrictions, this high-limit switch provides the exact electrical specifications and physical dimensions required to maintain system integrity and equipment safety protocols without compromising furnace performance.

• Fixed Thermal Calibration: Precise 170°F open and 150°F close setpoints prevent nuisance tripping while ensuring robust heat exchanger protection.
• OEM Compatibility: Designed specifically as a direct replacement for Rheem and Ruud furnace parts, ensuring correct fitment and terminal alignment.
• Auto Reset Mechanism: Provides seamless restoration of the heating cycle once temperatures drop below the 150°F threshold.
• Extended Insertion Depth: The 7-inch probe ensures the sensor is positioned correctly in the direct path of supply air for rapid response times.

What causes a limit switch like the 47-21711-10 to trip frequently?
Frequent tripping is typically indicative of restricted airflow, often caused by a heavily soiled air filter, an undersized duct system, or a failing blower motor. If the switch opens at temperatures below its 170°F rating, the internal bimetal disc may have fatigued, requiring a replacement.

Can this SPST limit switch be used in 24V and 120V circuits?
Yes, this switch is designed to handle standard HVAC control voltages. Technicians should always verify the amperage draw of the circuit to ensure it falls within the switch's rated capacity for board-mounted applications.

Does the 7-inch insertion length matter if the old part was shorter?
Yes. Insertion length is critical for accuracy. Using a switch with an incorrect probe depth can lead to delayed response times or premature failure, as the sensor will not be positioned in the optimal thermal zone of the furnace cabinet.

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.