Carrier HH18HA504 Limit Switch

The Carrier HH18HA504 Limit Switch is a critical OEM replacement part designed for high-limit temperature monitoring in HVAC furnaces. This automatic reset limit switch is engineered to open the burner control circuit when internal plenum temperatures reach the 180°F to 220°F threshold, effectively preventing heat exchanger damage and ensuring safe operational cycles. As a specialized furnace safety switch, this component features a cut-out temperature of 180°F and a cut-in temperature of 140°F, providing a reliable thermal response for residential and light commercial heating systems. The HH18HA504 serves as the direct 1:1 replacement for the legacy Carrier 1176907 model, maintaining the exact footprint and electrical specifications required for Factory Authorized Parts standards. For contractors, this bimetal snap-action switch ensures compatibility with a wide range of Carrier, Bryant, and Payne equipment, including the 58STA and PG8 series, facilitating a drop-in installation that restores system integrity without the need for field modifications.

• Precise Thermal Protection: Monitors air temperature with a calibrated 180-220 degree range to prevent overheating.
• Automatic Reset Logic: Features a snap-action 140°F cut-in reset, allowing the system to resume normal operation once safe temperatures are achieved.
• Direct OEM Compatibility: Engineered specifically to replace part 1176907, ensuring proper fit and terminal alignment.
• Durable Construction: Built to withstand the high-cycle demands of modern gas furnace heat exchangers.

Is the HH18HA504 a manual or automatic reset switch?
This is an automatic reset limit switch. It will automatically re-close the circuit once the sensed temperature drops to approximately 140°F, unlike manual reset rollout switches which require physical intervention.

Can I use this switch for a furnace with a different temperature rating?
No. You must match the L180-40 or 180-220 degree rating exactly to the manufacturer's specifications to ensure the furnace operates within its designed safety parameters.

What causes this limit switch to trip frequently?
Frequent tripping is often a symptom of restricted airflow, such as a dirty air filter, blocked return ducts, or a failing blower motor, rather than a defect in the switch itself.

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.