Description
The Lennox 57M66 is an OEM replacement pressure switch engineered to deliver reliable, accurate draft-proving protection in Lennox furnace and air handler applications. With a calibrated set point of 1.41″ water column (wc), this switch monitors the negative pressure generated by the inducer motor to confirm proper venting before allowing the ignition sequence to proceed — a critical safety function in modern induced-draft and condensing heating systems.
Key Features
- Set point: 1.41″ water column (wc)
- Switch type: SPST (Single-Pole, Single-Throw)
- Dual 1/4″ barb port connections for secure hose attachment
- OEM Lennox replacement part — ensures proper fit and function
- Monitors inducer draft pressure to verify safe venting conditions
- Prevents ignition if adequate negative pressure is not established
- Designed for use in Lennox induced-draft and condensing furnace systems
How It Works
The pressure switch is connected via rubber tubing to the inducer housing or collector box. When the inducer motor runs and creates the correct level of negative pressure (at or beyond the 1.41″ wc set point), the SPST switch closes, signaling the control board that safe venting conditions exist and allowing the heating sequence to continue. If pressure falls outside the acceptable range — due to a blocked flue, failed inducer, or collapsed hose — the switch remains open, locking out the furnace and protecting against unsafe operation.
Application
- Direct OEM replacement for Lennox furnaces and air handlers specifying part number 57M66
- Compatible with induced-draft and condensing furnace configurations
- Ideal for service technicians performing routine maintenance, troubleshooting, or component replacement
Why Choose OEM Lennox Parts?
Using genuine Lennox replacement components like the 57M66 ensures the pressure switch meets the exact factory specifications for your equipment. This protects system warranty, maintains peak efficiency, and reduces the risk of nuisance lockouts or unsafe operation caused by mismatched aftermarket parts.
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