Lennox 33W18 Pressure Switch
The Lennox 33W18 is a critical two-stage combustion air pressure switch designed for specific Lennox high-efficiency furnace models. This differential pressure switch ensures secondary heat exchanger safety by monitoring the inducer motor's draft performance. With a dual-setpoint configuration of 0.20" WC / 1.32" WC, this switch accurately sequences the low-fire and high-fire combustion cycles. Proper calibration of the Lennox 33W18 pressure switch is essential to prevent "watchguard" lockout codes and ensure stable ignition under various static pressure conditions. Built with high-grade diaphragms to resist fatigue, this replacement part restores factory-spec furnace safety circuit operation. When troubleshooting a furnace pressure switch stuck open, technicians should verify the specific inches of water column rating matches the nameplate of the original Honeywell or MPL branded OEM component to ensure compatibility with the gas valve's staging logic.
Technical Performance Benefits
- OEM Specific Calibration: Precisely tuned to 0.20" / 1.32" WC setpoints for Lennox 2-stage furnaces.
- Enhanced Safety Logic: Prevents combustion under restricted venting or heat exchanger blockage conditions.
- Rugged Diaphragm Construction: Engineered to withstand high-frequency cycling and temperature fluctuations within the burner cabinet.
- Direct Fit Installation: Features standard spade terminal connections for seamless integration into the existing HVAC wiring harness.
Common Contractor Questions
What causes a Lennox 33W18 switch to fail?
Most failures result from moisture accumulation in the sampling lines, cracked diaphragms, or restricted furnace venting causing the switch to trip outside its static pressure parameters.
Can I use a single-stage pressure switch to replace the 33W18?
No. The 33W18 pressure switch is a dual-stage component required for the control board to verify both low and high inducer speeds. A single-stage switch will cause fault codes on two-stage equipment.
How do I verify if the 33W18 is defective?
Use a manometer to measure the actual draft produced by the inducer and compare it against the 0.20" / 1.32" WC ratings while checking for electrical continuity across the terminals.
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.
Lennox 33W18 Pressure Switch
The Lennox 33W18 is a critical two-stage combustion air pressure switch designed for specific Lennox high-efficiency furnace models. This differential pressure switch ensures secondary heat exchanger safety by monitoring the inducer motor's draft performance. With a dual-setpoint configuration of 0.20" WC / 1.32" WC, this switch accurately sequences the low-fire and high-fire combustion cycles. Proper calibration of the Lennox 33W18 pressure switch is essential to prevent "watchguard" lockout codes and ensure stable ignition under various static pressure conditions. Built with high-grade diaphragms to resist fatigue, this replacement part restores factory-spec furnace safety circuit operation. When troubleshooting a furnace pressure switch stuck open, technicians should verify the specific inches of water column rating matches the nameplate of the original Honeywell or MPL branded OEM component to ensure compatibility with the gas valve's staging logic.
Technical Performance Benefits
- OEM Specific Calibration: Precisely tuned to 0.20" / 1.32" WC setpoints for Lennox 2-stage furnaces.
- Enhanced Safety Logic: Prevents combustion under restricted venting or heat exchanger blockage conditions.
- Rugged Diaphragm Construction: Engineered to withstand high-frequency cycling and temperature fluctuations within the burner cabinet.
- Direct Fit Installation: Features standard spade terminal connections for seamless integration into the existing HVAC wiring harness.
Common Contractor Questions
What causes a Lennox 33W18 switch to fail?
Most failures result from moisture accumulation in the sampling lines, cracked diaphragms, or restricted furnace venting causing the switch to trip outside its static pressure parameters.
Can I use a single-stage pressure switch to replace the 33W18?
No. The 33W18 pressure switch is a dual-stage component required for the control board to verify both low and high inducer speeds. A single-stage switch will cause fault codes on two-stage equipment.
How do I verify if the 33W18 is defective?
Use a manometer to measure the actual draft produced by the inducer and compare it against the 0.20" / 1.32" WC ratings while checking for electrical continuity across the terminals.
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.
Product Information
Product Information
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Description
The Lennox 33W18 is a critical two-stage combustion air pressure switch designed for specific Lennox high-efficiency furnace models. This differential pressure switch ensures secondary heat exchanger safety by monitoring the inducer motor's draft performance. With a dual-setpoint configuration of 0.20" WC / 1.32" WC, this switch accurately sequences the low-fire and high-fire combustion cycles. Proper calibration of the Lennox 33W18 pressure switch is essential to prevent "watchguard" lockout codes and ensure stable ignition under various static pressure conditions. Built with high-grade diaphragms to resist fatigue, this replacement part restores factory-spec furnace safety circuit operation. When troubleshooting a furnace pressure switch stuck open, technicians should verify the specific inches of water column rating matches the nameplate of the original Honeywell or MPL branded OEM component to ensure compatibility with the gas valve's staging logic.
Technical Performance Benefits
- OEM Specific Calibration: Precisely tuned to 0.20" / 1.32" WC setpoints for Lennox 2-stage furnaces.
- Enhanced Safety Logic: Prevents combustion under restricted venting or heat exchanger blockage conditions.
- Rugged Diaphragm Construction: Engineered to withstand high-frequency cycling and temperature fluctuations within the burner cabinet.
- Direct Fit Installation: Features standard spade terminal connections for seamless integration into the existing HVAC wiring harness.
Common Contractor Questions
What causes a Lennox 33W18 switch to fail?
Most failures result from moisture accumulation in the sampling lines, cracked diaphragms, or restricted furnace venting causing the switch to trip outside its static pressure parameters.
Can I use a single-stage pressure switch to replace the 33W18?
No. The 33W18 pressure switch is a dual-stage component required for the control board to verify both low and high inducer speeds. A single-stage switch will cause fault codes on two-stage equipment.
How do I verify if the 33W18 is defective?
Use a manometer to measure the actual draft produced by the inducer and compare it against the 0.20" / 1.32" WC ratings while checking for electrical continuity across the terminals.
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.
