Carrier HH18HA122 Limit Switch

The Carrier HH18HA122 Limit Switch acts as a critical safety component for residential and light commercial HVAC systems, specifically designed to monitor internal heat exchanger temperatures. This automatic reset limit switch features a fixed set point of 117-120°F, ensuring the burner circuit or blower operation is interrupted if thermal thresholds are exceeded. For technicians performing furnace repair or preventive maintenance, this OEM component provides precise calibration to prevent overheating and potential equipment damage. Built for durability in high-cycle environments, the Carrier HH18HA122 temperature switch ensures the system operates within manufacturer specifications. It serves as a direct drop-in replacement for various HVAC high limit applications across Carrier, Bryant, and Payne equipment, effectively resolving fault codes related to primary limit circuit trips. Proper installation is essential for maintaining safety protocols and optimizing the airflow circuit during the heating cycle.

Key Technical Benefits

• Factory-Calibrated Reset: Features a precise 117-120 degree Fahrenheit trip point for reliable thermal protection.
• OEM Compatibility: Specifically engineered for a perfect fit in Carrier, Bryant, and Payne gas furnaces and heat pumps.
• Automatic Reset Functionality: Automatically restores the electrical circuit once temperatures drop back to safe operating levels.
• Compact Form Factor: Designed for standard mounting configurations within the furnace cabinet for easy technician replacement.
• High-Temperature Housing: Constructed with industrial-grade materials to withstand the rigorous conditions inside the heat exchanger plenum.

Common Technical Questions

What causes a Carrier HH18HA122 to trip frequently?
Repeated tripping is usually indicative of restricted airflow, often caused by a dirty air filter, blocked return vents, or a failing blower motor. If the switch remains open after the unit cools, the internal bimetal disc may have failed.

Can I bypass this limit switch for testing purposes?
While jumpers can be used briefly to diagnose a faulty sensor, the switch must never be bypassed during normal operation. This component is a primary safety device designed to prevent heat exchanger cracks and fire hazards.

Is the HH18HA122 compatible with 80% and 90% efficiency furnaces?
Yes, this switch is utilized across various efficiency platforms, provided the temperature rating and mounting depth matches the original part number found in the service manual.

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.