Lochinvar & A.O. Smith 100109973 Switch

The Lochinvar & A.O. Smith 100109973 Blocked Inlet Switch is a critical safety component designed for high-efficiency condensing boilers and water heaters. As a normally closed air pressure switch, its primary function is to monitor the intake system for airflow restrictions. If the intake air connection screen becomes clogged or the vent piping is obstructed, the switch detects a fall in pressure and opens the electrical circuit, instantly shutting down the burner to prevent incomplete combustion or equipment damage. This genuine OEM replacement part is engineered to meet the specific activation setpoints required for Lochinvar Shield and A.O. Smith Cyclone BTH models, ensuring the combustion blower maintains the correct stoichiometric ratio for safe operation.

When troubleshooting a "Blocked Inlet" fault code, verify the integrity of the sensing tube and ensure no condensate has pooled in the lines before replacing the switch. This HVAC pressure switch is constructed with a durable housing and high-precision diaphragm to withstand the cycling demands of commercial and residential heating environments. Utilizing OEM heating repair parts like the 100109973 switch ensures full compatibility with the integrated control board and maintains the system's factory-specified safety parameters.

• Critical Safety Protection: Automatically disables the gas valve if inadequate combustion air is detected to prevent hazardous conditions.
• OEM Precision: Specifically calibrated for Lochinvar and A.O. Smith commercial water heaters to eliminate nuisance tripping.
• Reliable Construction: Features a robust normally closed contact configuration designed for long-term monitoring of the intake manifold.
• Simplified Diagnostics: Compatible with standard digital manometers for easy verification of activation pressure during routine maintenance.

What causes a blocked inlet switch to trip?
Common culprits include debris in the air intake adapter, excessive vent pipe length, too many elbows in the run, or a clogged intake screen. Always check for physical obstructions and the integrity of the sensing tube first.

Can I use a universal pressure switch instead of the 100109973?
It is not recommended. These switches have specific "make" and "break" pressure ratings measured in inches of water column. Using a non-OEM part can lead to unsafe operation or frequent system lockouts.

How do I test if the switch is defective?
Use a multimeter to check for continuity across the terminals while the system is off. If the switch remains open without a call for heat, or fails to open when a known blockage is simulated, the component requires replacement.

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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.