Lochinvar & A.O. Smith 100109934 Switch

The Lochinvar & A.O. Smith 100109934 Switch is a critical safety component engineered for high-efficiency condensing boilers and commercial water heaters. Functioning as a blocked outlet switch, this normally closed (NC) pressure sensor is calibrated to 2.6" WC to monitor exhaust backpressure. If the venting system becomes obstructed by debris, ice, or mechanical failure, the 100109934 triggers an immediate system lockout to prevent the hazardous accumulation of combustion gases and carbon monoxide. As a genuine OEM replacement part, it ensures precise integration with the Lochinvar Knight and A.O. Smith Cyclone control logic, maintaining the specific pressure differentials required for safe modulation. For technicians performing HVAC troubleshooting or routine maintenance, replacing a fouled or non-responsive flue pressure switch with this factory-spec component is essential for restoring reliable ignition sequences and preventing nuisance codes during the pre-purge cycle. This switch is built to withstand the corrosive environment of flue condensates, ensuring long-term boiler system safety and operational integrity.

• Precise 2.6" WC Calibration: Factory-set to detect specific exhaust obstructions, preventing dangerous flue gas spillage.
• OEM Compatibility: Drop-in replacement for Lochinvar and A.O. Smith units, ensuring the control board receives accurate millivolt or line voltage signals.
• System Protection: Acts as a primary safety limit switch to shut down the burner before pressure imbalances damage the heat exchanger.
• Rugged Construction: Designed for high-cycle reliability in commercial and residential condensing water heaters.

• What causes a blocked outlet switch lockout? Lockouts are typically caused by physical obstructions in the vent pipe, excessive vent length exceeding manufacturer specs, or a failed switch diaphragm.
• Can I bypass the 100109934 for testing? Bypassing safety switches is never recommended. Always use a manometer to verify actual flue pressure against the 2.6" WC rating before replacing the switch.
• Does this part replace older A.O. Smith part numbers? Yes, the 100109934 is the current OEM replacement for legacy numbers including 193362 and 9004549215.

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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.