Reznor 104842 Pressure Switch

The Reznor 104842 Pressure Switch is a critical safety component designed for combustion air proving in specialized industrial heating equipment, including Reznor waste oil heaters and Venturion models. Engineered to monitor the differential pressure within the induced draft assembly, this air pressure switch (often cross-referenced as FS3440-894) ensures that proper venting is established before allowing the burner to cycle. By verifying airflow through the heat exchanger, it prevents unsafe operation due to blocked flues or motor failure.

For contractors servicing HVAC induction systems, the 104842 is a genuine OEM replacement part specifically tuned for Reznor RA, RAD, and RV unit heaters. It features a precise set-point factory-calibrated to maintain system integrity under varying load conditions. Replacing a failed switch with this original equipment ensures reliable draft proving and prevents intermittent lockouts. The durable housing is built to withstand the rigorous temperatures and soot exposure common in commercial gas-fired and waste oil environments, providing accurate differential pressure sensing for long-term field stability.

• Direct Fit Compatibility: Specifically engineered for Reznor RA, RAD, and RV series heaters, ensuring seamless integration with existing wiring harnesses.
• Safety Interlock Reliability: Precisely monitors combustion air pathway pressure to prevent burner ignition under inadequate venting conditions.
• OEM Engineering: Replaces Reznor 104842 and FS3440-894, maintaining factory specifications for air pressure proving.
• Industrial Grade Construction: Designed to handle the high-cycle demands of waste oil heating systems without signal drift.

• How do I know if the pressure switch is causing a furnace lockout? Check for a specific blink code on the ignition module; if the inducer motor is running but the igniter doesn't glow, verify the differential pressure at the switch ports using a manometer.
• Can I use a generic adjustable switch instead of the Reznor 104842? It is not recommended. This OEM switch is factory-set to a specific WC (water column) threshold crucial for the safe operation of induced draft unit heaters.
• Which Reznor models use this specific part? This switch is commonly found in RA and RAD 110, 140, 150, 250, 235, 350 and RV 225, 325 models.

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.