Lochinvar & A.O. Smith 100208378 Pressure Switch

The Lochinvar & A.O. Smith 100208378 Pressure Switch is a critical OEM safety component engineered for precise airflow monitoring in high-efficiency boilers and water heating systems. This switch is factory-calibrated to a 4.10" WC (Water Column) set point, ensuring the inducer fan generates sufficient negative pressure for safe combustion. As a direct cross-reference for part 100166100, it serves as a standard replacement for several Lochinvar Knight and A.O. Smith SNA series models, including the AWN199, AWN399, KBN210, and KBN399. By verifying vent pressure before allowing the ignition sequence, this switch prevents hazardous operation during flue blockages or fan failures. The 100208378 pressure switch is constructed for high-cycle reliability in demanding commercial and residential HVACR environments, maintaining stringent safety compliance without compromising system uptime.

• Exact OEM Calibration: Pre-set at 4.10" WC to match original factory specifications for Lochinvar and A.O. Smith equipment.
• Broad Compatibility: Serves as a verified replacement for 100166100, PRS20002, and PRS20002K, streamlining truck stock.
• Enhanced Safety Logic: Prevents the burner from firing if improper venting or obstructed airflow is detected, protecting the heat exchanger.
• Rugged Build Quality: Designed to withstand the thermal stress and rapid cycling typical of modern condensing boilers.
• Drop-in Installation: Features standard terminal connections and mounting brackets for efficient field replacement.

What happens if the pressure switch fails to close?
If the 100208378 switch remains open, the control board will typically trigger a lockout code (such as 'Air Pressure Switch Did Not Close'). This usually indicates a failing inducer motor, an obstruction in the vent pipe, or a cracked pressure sensing tube.

Can I use this to replace a switch with a different WC rating?
No. Pressure switches are safety-critical components. Using a switch with a different Water Column rating than specified by the manufacturer can lead to delayed ignition or unsafe combustion levels. Always verify the 4.10" WC requirement on your unit's rating plate.

How do I test the 100208378 pressure switch?
Technicians should use a digital manometer to verify the actual draft pressure produced by the inducer and a multimeter to check for continuity across the terminals when the set point is reached.

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.