Carrier HH18HA187 Automatic Limit Switch, 80–180°F

Description

The Carrier HH18HA187 is an OEM automatic limit switch engineered to protect furnaces and heating systems from dangerous overheating conditions. Designed as a direct replacement for select Carrier heating equipment, this limit switch monitors heat exchanger temperatures and automatically interrupts the burner circuit when temperatures exceed safe operating thresholds — then resets automatically once temperatures return to the normal operating range.

How It Works

The limit switch continuously monitors the air temperature within the furnace plenum or heat exchanger area. If the sensed temperature rises above the set point, the switch opens the control circuit, shutting off the burner to prevent equipment damage, heat exchanger cracking, or potential fire hazards. The automatic reset feature means the switch will close again once temperatures drop back to a safe level, restoring normal furnace operation without requiring manual intervention.

Key Features

• OEM Carrier replacement part — SKU HH18HA187
• Temperature operating range: 80°F to 180°F
• Automatic reset — no manual reset required after trip
• Protects heat exchanger and furnace components from thermal damage
• Direct OEM replacement for compatible Carrier furnace models
• Reliable bimetal or disc-type sensing element for accurate temperature response
• Helps maintain system efficiency and extend equipment service life

Application

• Compatible with select Carrier gas and oil furnace models
• Suitable for residential and light commercial heating applications
• Designed for installation in furnace plenum or heat exchanger limit switch mounting location

Why Replace Your Limit Switch?

A faulty limit switch can cause nuisance shutdowns, prevent the furnace from firing, or — if it fails in the closed position — allow the system to overheat. Replacing a worn or failed limit switch with a genuine Carrier OEM part ensures proper calibration, reliable protection, and full compatibility with your existing equipment.

Always consult the equipment’s service manual and verify compatibility with your specific furnace model before installation. Installation should be performed by a qualified HVAC technician.