Carrier HH12ZB170 Limit Switch

The Carrier HH12ZB170 Limit Switch is a critical safety component designed for precise thermal monitoring in high-efficiency furnace and air handling units. This OEM replacement limit switch features a fixed temperature range, engineered to open at 170°F and automatically reset when temperatures drop to 130°F. As an L170-40F thermal switch, it provides essential protection against heat exchanger overheating by interrupting the burner circuit if airflow is restricted or the blower motor fails. The HH12ZB170 automatic reset switch is constructed with a durable bimetal sensing element and silver-alloy contacts to ensure reliable electrical continuity and long-term cycling performance. When troubleshooting furnace limit trips, ensure the static pressure and filter condition are within spec, as this HVAC high-limit sensor is calibrated for tight tolerances to match original equipment manufacturer safety standards. Professional installation is required to ensure proper insertion depth and electrical connection within the low-voltage control string.

• Precise Thermal Calibration: Fixed 170-degree trip point ensures the system shuts down before heat exchanger damage occurs.
• Automatic Reset Functionality: The 40-degree differential allows the 130-degree reset to restore operation once safe temperatures are reached.
• OEM Compatibility: Exact drop-in replacement for Carrier, Bryant, and Payne units, eliminating the need for bracket modifications.
• Industrial Grade Build: High-temperature housing and spade terminals are designed for the demanding environment of a furnace plenum.

What causes a limit switch like the HH12ZB170 to trip frequently?
Repeated tripping is usually indicative of restricted airflow, such as a clogged media filter, a failing blower capacitor, or undersized ductwork causing high static pressure.

Can I bypass this limit switch for testing?
Temporary jumping for diagnostic purposes is standard practice to verify a faulty sensor versus an actual high-heat condition, but the unit must never be left in operation without a functional limit switch in the safety circuit.

Is this switch compatible with other brands?
While designed for Carrier family equipment, this limit switch can be used in other applications requiring an L170-40F specification, provided the mounting orientation and terminal sizing match.

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.