Description
The Lochinvar & A.O. Smith 100277772 is an OEM replacement air pressure switch engineered specifically for F9 series water heaters and boilers operating at high-altitude installations. This switch monitors combustion air pressure to verify that the inducer blower is generating adequate airflow before and during burner operation — a critical safety function that prevents unsafe ignition conditions.
Designed for high-altitude environments where reduced air density can affect combustion performance, this switch is calibrated to the precise pressure thresholds required for reliable F9 series operation at elevation. It integrates directly with the unit’s control board, providing a proven interlock that keeps the system running safely and efficiently.
Key Features
- OEM replacement part for Lochinvar & A.O. Smith F9 series units
- Calibrated for high-altitude installations where air pressure is reduced
- Monitors inducer blower operation to confirm adequate combustion airflow
- Provides safety interlock to prevent ignition without proper draft
- Direct drop-in replacement for fast, reliable service
- Engineered to OEM specifications for consistent performance
Application
- Compatible with Lochinvar & A.O. Smith F9 series water heaters and boilers
- Designed for high-altitude installation environments
- Replaces worn, failed, or out-of-spec pressure switches
Why Choose OEM?
Using a genuine Lochinvar & A.O. Smith replacement switch ensures the pressure setpoint is factory-calibrated for your specific unit and altitude range. Aftermarket substitutes may carry incorrect trip points, leading to nuisance lockouts or — more critically — unsafe operation. SKU 100277772 delivers the exact fit, form, and function required to restore your F9 series unit to peak performance.







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