Lochinvar & A.O. Smith 100109816 Pressure Switch

The Lochinvar & A.O. Smith 100109816 Pressure Switch is a critical OEM replacement part engineered for precise atmospheric monitoring in high-efficiency commercial water heaters and boilers. Calibrated to a 6.5" WC (Water Column) set point, this differential pressure switch acts as a safety-critical flue prover, ensuring the combustion blower is generating sufficient negative pressure to safely vent exhaust gases. Designed for compatibility with select A.O. Smith, Lochinvar, and State units, this 100109816 gas pressure switch prevents the burner from igniting if a blocked vent or intake restriction is detected, protecting the heat exchanger from thermal stress and soot accumulation.

For service contractors, this genuine 100109816 switch ensures factory-spec combustion safety and eliminates the liability associated with generic alternatives. The robust diaphragm construction and snap-action electrical contacts are built to withstand the rapid cycling and high-temperature environments of commercial water heating systems. Always verify the model and serial number before installation, as this 6.5-inch WC switch is specifically tuned for high-performance venting requirements.

• OEM Precision: Genuine Lochinvar and A.O. Smith 100109816 factory part ensures exact 6.5" WC trip points for system safety.
• System Protection: Actively monitors for blocked flue or intake air restrictions, preventing unsafe combustion cycles.
• Broad Compatibility: Replaces part number 9004360115 and is compatible with various AO Smith FPS-40-225 and commercial boiler models.
• Durable Construction: High-grade internal diaphragm designed for long-term HVACR reliability in demanding commercial applications.

Is the 100109816 pressure switch adjustable for high-altitude installs?
This specific 6.5" NC pressure switch is factory-calibrated for specific venting and blower configurations. Manual adjustments should not be performed; instead, verify the unit's required set point against the HVAC technical specs for your specific elevation.

What are the symptoms of a failing 100109816 switch?
Common indicators include the inducer motor running without the igniter sparking, or a specific "Pressure Switch Stuck Open/Closed" fault code on the integrated control board.

Can I use a universal pressure switch instead of the 100109816?
Using a universal switch is not recommended. The 100109816 is a model-specific safety control; installing a part with an incorrect WC rating can lead to carbon monoxide leakage or premature heat exchanger failure.

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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.