Carrier HH18HA123 Switch

The Carrier HH18HA123 Switch is a high-precision Limit Switch Assembly engineered to monitor high-limit temperatures within residential and commercial HVAC systems. This genuine OEM replacement part is critical for equipment safety, designed to automatically interrupt the electrical circuit if the heat exchanger exceeds safe operating parameters. Manufactured by Klixon for Carrier, this switch features a manual reset or automatic function depending on the specific furnace configuration, calibrated with a cut-out temperature of 175°F and a cut-in temperature of 135°F. Its compact 2-inch by 1.5-inch footprint allows for seamless integration into the tight tolerances of modern blower compartments. Veteran technicians rely on the HH18HA123 to prevent thermal stress on the heat exchanger, ensuring the system operates within its design limits while maintaining consistent airflow safety. This HVAC temperature limit switch is compatible with a wide range of Carrier, Bryant, and Payne equipment, providing a reliable solution for restoring furnace sequence of operation.

• Precise Thermal Calibration: Features a fixed 175°F trip point to prevent heat exchanger overheating and potential cracked cells.
• OEM Integrity: Ensures exact electrical specifications and mounting alignment, reducing installation time for field service.
• Enhanced System Safety: Functions as a primary safety control to shut down the gas valve or heating elements during restricted airflow conditions.
• Broad Compatibility: Standard furnace limit switch for many Carrier-produced air handlers and gas furnaces.

Is the Carrier HH18HA123 an automatic or manual reset switch?

This specific model is typically an automatic reset switch that restores the circuit once the plenum temperature drops to 135°F, though it is often used in series with other primary safety controls.

What causes this limit switch to trip frequently?

Frequent tripping usually indicates restricted return air, a dirty filter, an oversized furnace for the ductwork, or a failing indoor blower motor causing the heat exchanger to overheat.

Can I bypass this switch for testing?

Bypassing safety controls is never recommended for permanent operation. Use a multimeter to check for continuity across the terminals to verify if the switch is open or closed during the startup sequence.

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.