Description
The Lennox 78W57 is a precision-engineered pressure switch designed as a direct OEM replacement for compatible Lennox heating systems. Monitoring flue gas pressure to confirm proper inducer operation, this switch is a critical safety component that prevents furnace operation under unsafe venting conditions.
Key Features
- Set point: 0.27″ water column (“wc) — factory-calibrated for precise pressure sensing
- SPST (Single-Pole, Single-Throw) switching action for straightforward open/close control
- 1/4″ barb port connection for secure, leak-free hose attachment
- OEM Lennox replacement part — engineered to exact factory specifications
- Ensures safe furnace operation by verifying inducer draft before allowing ignition
- Compact design for easy installation in tight furnace cabinet spaces
How It Works
The 78W57 pressure switch monitors the negative pressure (draft) created by the inducer blower motor. When adequate draft is confirmed at the 0.27″ wc threshold, the SPST contacts close, signaling the control board to proceed with the ignition sequence. If draft pressure is insufficient — due to a blocked flue, failed inducer, or collapsed hose — the switch remains open, locking out the furnace and protecting against unsafe combustion conditions.
Application
- Compatible with select Lennox gas furnace models
- Replaces failed or out-of-spec OEM pressure switches
- Ideal for HVAC technicians performing routine maintenance or diagnostic repairs
Why Choose the Lennox 78W57
Using a genuine Lennox OEM pressure switch ensures proper calibration, reliable switching, and compatibility with your system’s control board — eliminating the guesswork of aftermarket alternatives. Keep your furnace operating safely and efficiently with this factory-spec replacement.
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