Carrier HH12ZZ150 L150-40F Limit Switch

Description

Carrier HH12ZZ150 L150-40F Limit Switch Overview

The Carrier HH12ZZ150 is an OEM-grade high-limit switch engineered to protect furnaces and heating systems from dangerous overheating conditions. Designated as the L150-40F model, this limit switch is calibrated to open at 150°F and features a 40°F differential, meaning it automatically resets and closes at approximately 110°F once safe operating temperatures are restored. It is a direct factory replacement for Carrier systems, ensuring precise fit and reliable performance.

How It Works

The limit switch continuously monitors supply-air or heat exchanger temperatures. If temperatures exceed the 150°F set point — due to restricted airflow, a dirty filter, or a blower malfunction — the switch opens the control circuit, shutting down the burner to prevent heat exchanger damage or fire hazard. Once temperatures drop back to the reset point, the switch automatically closes, restoring normal operation.

Key Features

• OEM Carrier replacement part — direct drop-in fit for compatible Carrier furnace models
• Opens (trips) at 150°F to protect against overheating
• 40°F differential — automatically resets at approximately 110°F
• Reliable bimetal disc sensing element for accurate, repeatable temperature response
• Helps safeguard heat exchangers, burner assemblies, and surrounding components
• Essential safety control for residential and light-commercial forced-air furnaces

Specifications

• Brand: Carrier
• Part Number / SKU: HH12ZZ150
• Model: L150-40F
• Set Point (Opens): 150°F
• Differential: 40°F
• Reset Point (Closes): ~110°F
• Type: Auto-reset high-limit switch
• Application: Forced-air furnace high-limit protection

Application

Designed for use in Carrier forced-air gas furnaces, this limit switch is a critical safety component that should be replaced promptly if found to be faulty. Always verify compatibility with your specific furnace model before installation. Consult your equipment’s wiring diagram and service manual for proper installation procedures.