Lochinvar & A.O. Smith 100208404 Pressure Switch

The Lochinvar & A.O. Smith 100208404 Pressure Switch is a critical safety component designed for high-efficiency water heaters and boilers. As a genuine OEM replacement part, it is functionally identical to the PRS2704, ensuring a precise fit and reliable performance for troubleshooting blocked flue or venting issues. This differential air pressure switch monitors the pressure across the combustion blower to verify proper airflow before allowing the ignition sequence to proceed. Its primary function is to prevent hazardous conditions such as backdrafts or improper combustion by interrupting the circuit if the inducer motor fails to pull sufficient vacuum or if the exhaust becomes obstructed. Built with a high-quality internal diaphragm and corrosion-resistant sensing ports, the 100208404 provides the accurate activation pressure required for A.O. Smith Cyclone BTH and Lochinvar Knight series models. For service technicians, utilizing this HVAC replacement pressure switch ensures system integrity and avoids the nuisance lockouts common with generic alternatives.

• OEM Compatibility: Exact replacement for the PRS2704, specifically calibrated for Lochinvar and A.O. Smith commercial and residential units.
• Ignition Safety: Ensures the combustion air fan is operating at the correct RPM and airflow before the gas valve opens.
• Durable Construction: Engineered to withstand high-temperature environments and resist moisture buildup within the sensing lines.
• Reliable Troubleshooting: Eliminates "Air Pressure Switch Open" (APS) error codes when paired with a properly functioning inducer.

What causes a 100208404 switch to fail during the pre-purge cycle?
Failure often occurs due to a ruptured internal diaphragm, moisture in the sensing tubes, or an obstructed vent pipe. Technicians should use a digital manometer to verify the actual pressure against the switch's set point before replacing.

Can I use this switch as a substitute for other brands' differential switches?
This switch is specifically calibrated for Lochinvar and A.O. Smith technical specifications. While it may look similar to others, the specific W.C. (Water Column) trip point is vital for safe appliance operation; always match the part number 100208404 or PRS2704.

How do I verify if the switch or the blower is at fault?
Check for 120VAC at the inducer motor first. If the motor is running but the pressure switch contacts remain open, inspect the sensing ports and vent runs for blockages before assessing the switch's continuity.

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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.