Carrier HH18HV120 Limit Switch

The Carrier HH18HV120 Limit Switch is a critical safety component designed for precise thermal regulation within HVAC systems, specifically for Carrier, Bryant, and Payne furnace models. This OEM replacement part operates as an automatic reset thermal disc, calibrated to open the circuit when temperatures reach 120°F and close (auto-reset) when they drop to 90°F. As a veteran technician knows, maintaining the integrity of the furnace high limit switch is essential for preventing heat exchanger soot buildup and protecting the blower motor assembly from thermal overstress.

Constructed with a durable thermal disc sensor and designed for horizontal or multi-position mounting, the Carrier HH18HV120 ensures your HVAC safety controls remain responsive to rapid temperature fluctuations. Whether you are troubleshooting a 33-code fault on a Carrier board or conducting routine maintenance on an RTU (Rooftop Unit), this 90-120F auto limit switch provides the exact electrical specifications required to maintain factory-spec pressure and airflow safety margins. Relying on genuine Carrier parts eliminates the calibration drift often found in universal aftermarket alternatives, ensuring long-term system reliability.

• Precise Thermal Calibration: Features a fixed 120°F open and 90°F close range to verify safe operating parameters for gas-fired furnaces and electric heaters.
• Automatic Reset Functionality: Eliminates the need for manual intervention after a temporary overheat condition, restoring HVAC system operation once safe temperatures are reached.
• Broad Compatibility: Fits a wide range of popular models including 48HJM, 48DJE, and 580FPV series, making it a staple for commercial HVAC service vans.
• Easy Installation: Standard two-terminal connection and compact footprint allow for quick field replacement in tight burner vestibules.

What causes a Carrier HH18HV120 to trip prematurely?
Repeated tripping typically points to restricted airflow, often caused by a dirty furnace filter, a failing blower motor, or a clogged secondary heat exchanger. Always check static pressure when replacing this switch.

Can this limit switch be used in place of a manual reset switch?
No. This is an auto-reset switch. Safety protocols require that you always replace a limit control with the exact OEM temperature rating and reset type specified by the manufacturer's data tag.

How do I verify if my HH18HV120 is faulty?
Perform a continuity test with a multimeter. If the switch shows an open circuit at room temperature, the internal bimetal disc has failed or reached its end of life and requires immediate replacement.

This item is not eligible for free shipping.

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.