Lochinvar & A.O. Smith 100208407 Switch

The Lochinvar & A.O. Smith 100208407 Blocked Flue Switch is a critical safety component designed for high-efficiency condensing boilers and water heaters. As a factory-authorized replacement for PRS2708 and PRS2708K, this blocked flue pressure switch is calibrated to a specific 55" WC set point to detect dangerous venting restrictions. When flue gases cannot exit the heat exchanger due to obstructions like bird nests, ice, or excessive condensate buildup, this HVAC safety switch interrupts the 24V circuit to the gas valve, preventing combustion and potential carbon monoxide hazards.

For contractors servicing Lochinvar Knight or A.O. Smith residential and commercial units, maintaining the integrity of the safety loop is non-negotiable. This differential pressure switch monitors the pressure drop across the venting system, ensuring the inducer motor is moving air effectively. Before replacing, technicians should verify the intake and exhaust terminations are clear and the pressure tubing is free of moisture or cracks. This OEM part ensures drop-in compatibility and preserves the original equipment's sequence of operation for reliable boiler venting protection.

Key Benefits:

• Precise Calibration: Factory-set to 55" WC to ensure accurate lockout during venting failures.
• Direct OEM Replacement: Identical to Lochinvar PRS2708 and PRS2708K for seamless integration into the control board logic.
• Enhanced Safety: Acts as a primary fail-safe to prevent flue gas recirculation and overheating.
• Durable Construction: Engineered to withstand the corrosive environment of high-efficiency exhaust streams.

Common Questions:

What causes a blocked flue switch to trip?
Most trips result from external obstructions in the vent termination, a failing inducer motor, or a cracked heat exchanger. It can also be triggered by a kinked or water-logged pressure tube.

Can I use a universal pressure switch instead of the 100208407?
Using a universal switch is not recommended. The 100208407 has a specific 55" WC rating required by the manufacturer to ensure the appliance operates within its safety parameters.

How do I test if the 100208407 switch is faulty?
Use a manometer to measure the actual pressure at the switch port while the inducer is running. If the pressure exceeds the set point but the switch fails to close, or if it stays closed without pressure, the component requires replacement.

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.