Lennox 29M74 Limit Switch
The Lennox 29M74 Limit Switch is a critical fixed-temperature safety component engineered for Lennox furnace flame rollout and primary limit protection. This SPST (Single Pole Single Throw) thermal switch is rated for a 140°F trip point with a 30°F differential, ensuring precise furnace cycling and preventing heat exchanger damage. Designed as a direct OEM replacement limit switch, the 29M74 features a 1-inch insertion depth and 1/4-inch quick-connect terminals for seamless integration into existing HVAC control circuits. Maintaining a functional high-limit safety switch is essential for preventing hazardous overheating conditions in gas-fired heating systems. When troubleshooting Lennox furnace limit switch resets or "open limit" fault codes, technicians prioritize this part for its reliability and adherence to original factory specifications. This switch acts as a normally closed contact that opens upon reaching its thermal threshold, providing mechanical fail-safe protection for residential and light commercial air handlers.
Technical Specifications & Benefits
- Fixed Temperature Setting: Opens at 140°F to prevent overheating and closes at 110°F (30°F differential).
- OEM Compatibility: Exact replacement for Lennox 29M74, ensuring correct fitment and mounting hole alignment.
- Reliable SPST Logic: Simplified circuit integration with standard HVAC terminal connections.
- Durable Construction: Built to withstand the high-temperature environment of the furnace cabinet without drifting from calibrated setpoints.
Common Questions
How do I know if my Lennox furnace limit switch is bad?
If your furnace blower runs continuously while the burners stay off, or if the system cycles on high-limit error codes, the switch may be stuck open or failing to reset. Use a multimeter to check for continuity across the terminals when the switch is cool.
What causes a limit switch to trip repeatedly?
Frequent tripping usually indicates restricted airflow due to a dirty filter, blocked return vents, or a failing blower motor, causing heat to build up beyond the 140°F threshold.
Is the 29M74 a manual or automatic reset switch?
This specific model is an automatic reset limit switch, meaning it will re-close the circuit once the plenum temperature drops below the 30°F differential point.
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.
Original: $15.06
-65%$15.06
$5.27Lennox 29M74 Limit Switch
The Lennox 29M74 Limit Switch is a critical fixed-temperature safety component engineered for Lennox furnace flame rollout and primary limit protection. This SPST (Single Pole Single Throw) thermal switch is rated for a 140°F trip point with a 30°F differential, ensuring precise furnace cycling and preventing heat exchanger damage. Designed as a direct OEM replacement limit switch, the 29M74 features a 1-inch insertion depth and 1/4-inch quick-connect terminals for seamless integration into existing HVAC control circuits. Maintaining a functional high-limit safety switch is essential for preventing hazardous overheating conditions in gas-fired heating systems. When troubleshooting Lennox furnace limit switch resets or "open limit" fault codes, technicians prioritize this part for its reliability and adherence to original factory specifications. This switch acts as a normally closed contact that opens upon reaching its thermal threshold, providing mechanical fail-safe protection for residential and light commercial air handlers.
Technical Specifications & Benefits
- Fixed Temperature Setting: Opens at 140°F to prevent overheating and closes at 110°F (30°F differential).
- OEM Compatibility: Exact replacement for Lennox 29M74, ensuring correct fitment and mounting hole alignment.
- Reliable SPST Logic: Simplified circuit integration with standard HVAC terminal connections.
- Durable Construction: Built to withstand the high-temperature environment of the furnace cabinet without drifting from calibrated setpoints.
Common Questions
How do I know if my Lennox furnace limit switch is bad?
If your furnace blower runs continuously while the burners stay off, or if the system cycles on high-limit error codes, the switch may be stuck open or failing to reset. Use a multimeter to check for continuity across the terminals when the switch is cool.
What causes a limit switch to trip repeatedly?
Frequent tripping usually indicates restricted airflow due to a dirty filter, blocked return vents, or a failing blower motor, causing heat to build up beyond the 140°F threshold.
Is the 29M74 a manual or automatic reset switch?
This specific model is an automatic reset limit switch, meaning it will re-close the circuit once the plenum temperature drops below the 30°F differential point.
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.
Product Information
Product Information
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Description
The Lennox 29M74 Limit Switch is a critical fixed-temperature safety component engineered for Lennox furnace flame rollout and primary limit protection. This SPST (Single Pole Single Throw) thermal switch is rated for a 140°F trip point with a 30°F differential, ensuring precise furnace cycling and preventing heat exchanger damage. Designed as a direct OEM replacement limit switch, the 29M74 features a 1-inch insertion depth and 1/4-inch quick-connect terminals for seamless integration into existing HVAC control circuits. Maintaining a functional high-limit safety switch is essential for preventing hazardous overheating conditions in gas-fired heating systems. When troubleshooting Lennox furnace limit switch resets or "open limit" fault codes, technicians prioritize this part for its reliability and adherence to original factory specifications. This switch acts as a normally closed contact that opens upon reaching its thermal threshold, providing mechanical fail-safe protection for residential and light commercial air handlers.
Technical Specifications & Benefits
- Fixed Temperature Setting: Opens at 140°F to prevent overheating and closes at 110°F (30°F differential).
- OEM Compatibility: Exact replacement for Lennox 29M74, ensuring correct fitment and mounting hole alignment.
- Reliable SPST Logic: Simplified circuit integration with standard HVAC terminal connections.
- Durable Construction: Built to withstand the high-temperature environment of the furnace cabinet without drifting from calibrated setpoints.
Common Questions
How do I know if my Lennox furnace limit switch is bad?
If your furnace blower runs continuously while the burners stay off, or if the system cycles on high-limit error codes, the switch may be stuck open or failing to reset. Use a multimeter to check for continuity across the terminals when the switch is cool.
What causes a limit switch to trip repeatedly?
Frequent tripping usually indicates restricted airflow due to a dirty filter, blocked return vents, or a failing blower motor, causing heat to build up beyond the 140°F threshold.
Is the 29M74 a manual or automatic reset switch?
This specific model is an automatic reset limit switch, meaning it will re-close the circuit once the plenum temperature drops below the 30°F differential point.
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.
