Reznor 221158 Limit Switch

The Reznor 221158 is a professional-grade 145°F manual reset limit switch designed for critical thermal protection in industrial and commercial HVAC systems. This genuine Reznor OEM component acts as a primary safety control, monitoring the heat exchanger and air plenum to prevent hazardous overheating conditions. Engineered with a fixed 145-degree Fahrenheit trip point, the switch interrupts the control circuit if internal temperatures exceed the safe operating threshold. Unlike auto-reset models, this M/R limit switch requires a physical reset by a technician, ensuring that any airflow or combustion issues are diagnosed before the heating cycle resumes. This high-limit safety switch is vital for maintaining the structural integrity of the heat exchanger and ensuring system reliability during high-demand cycles. It is built for a direct fit in specific Reznor unit heaters and duct furnaces where precise temperature regulation and fail-safe operation are mandatory.

• OEM Precision: Guaranteed compatibility with Reznor equipment for seamless HVAC replacement part integration.
• Manual Reset Safety: Prevents automatic restrike, forcing a physical inspection of the blower or filter if a trip occurs.
• 145°F Threshold: Calibrated for high-accuracy thermal sensing to protect sensitive heating system components.
• Fail-Safe Design: Maintains an open circuit upon activation to eliminate the risk of continuous overheating or flame rollout.
• Direct Application: Standard footprint for quick mounting on existing limit brackets within the heater cabin.

What typically causes this 145F limit switch to trip?
Tripping is most frequently caused by restricted airflow. Common culprits include clogged air filters, a failing blower motor, or obstructed supply/return ducts. Because this is a manual reset switch, you must resolve the airflow issue before pressing the button.

How can I verify if the 221158 switch is faulty?
With the furnace power off and the system cooled, use a multimeter to check for continuity across the terminals. If the switch remains open (no continuity) after the reset button has been firmly pressed and the unit is cool, the internal contacts have likely failed and the switch requires replacement.

Can I replace a manual reset limit with an auto-reset model?
No. Safety controls must always match the original manufacturer specifications. Replacing a manual reset switch with an auto-reset version can mask serious underlying mechanical failures, potentially leading to equipment damage or unsafe operating conditions.

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.