Carrier HH19ZA135 Limit Switch

For contractors servicing Carrier residential and light commercial equipment, the Carrier HH19ZA135 Limit Switch is a critical safety component designed for precise thermal monitoring. This fixed-temperature furnace limit control features an L135-40F calibration, meaning the contacts are normally closed and will open on a temperature rise at 135°F, automatically resetting once the temperature drops below the 40°F differential. This genuine OEM Carrier Bryant Payne replacement part ensures exact electrical characteristics and structural integrity when replacing a fouled or sticking safety switch. Engineered for high-cycle reliability, the HH19ZA135 thermal switch protects the heat exchanger from overheating conditions caused by restricted airflow or blower failure. When troubleshooting furnace limit switch tripping, verifying the 135-degree setpoint against the system's manifold pressure and static pressure is essential for long-term reliability. This HVAC high-limit safety utilizes a bimetal disc for responsive thermal sensing, ensuring the combustion circuit is interrupted immediately upon reaching critical temperature thresholds.

• Precise Thermal Calibration: Factory-set L135-40F specs eliminate the need for field adjustments and ensure accurate high-limit protection.
• OEM Compatibility: Designed specifically for Carrier, Bryant, and Payne furnaces, ensuring the mounting bracket and terminal orientation align with original factory wiring.
• Enhanced Equipment Safety: Prevents heat exchanger fatigue and potential fire hazards by maintaining strict control over plenum temperatures.
• Durable Construction: Built to withstand the constant thermal cycling of high-efficiency gas furnaces without drift in trip points.

What causes a 135-degree limit switch to trip repeatedly?
Frequent tripping is usually indicative of restricted airflow. Check for a dirty HVAC air filter, a clogged secondary heat exchanger, or a failing blower motor that is not moving enough CFM to dissipate heat.

Can I bypass this switch for testing purposes?
A limit switch is a safety device. While a technician may momentarily jump the terminals to confirm a diagnosis, the system must never be left operating without a functional HH19ZA135 limit control in place.

Is the HH19ZA135 an automatic or manual reset?
This is an automatic reset switch. Once the temperature falls 40°F below the trip point, the bimetal disc will snap back to the closed position, re-establishing the 24V circuit to the integrated furnace control.

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.