OEM Lennox Limit Switch — 56W21
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The genuine OEM Lennox 56W21 limit switch is a high-temperature safety control for your Lennox gas furnace. Positioned to read heat-exchanger and plenum temperatures, it opens the burner circuit whenever operating heat climbs past the safe limit, protecting the furnace from damage due to restricted airflow, clogged filters, or a failing blower motor. Each 56W21 is factory-calibrated to the trip point specific to your Lennox model.
Common failure symptoms: A failing 56W21 typically shows up as short cycling, nuisance high-limit lockouts, or a furnace that heats briefly then shuts off. You may also experience the blower running continuously, inconsistent heat output, or complete no-heat lockouts after multiple failed cycles.
Why OEM matters: Because the limit switch is a safety-critical part, its calibration must be exact. Universal replacements with incorrect trip temperatures risk either unnecessary shutdowns or inadequate overheat protection for the heat exchanger. The OEM 56W21 guarantees the precise temperature rating, electrical connections, and physical fit your Lennox equipment demands for safe, reliable heating.
Shipping Information
- Orders placed before 3PM CST ship same business day
- Standard delivery: 2-5 business days
- Express shipping available at checkout
- Free shipping on orders over $75
- Tracking number emailed upon shipment
Return Policy
- 30-day returns on unused parts in original packaging
- Electrical parts (capacitors, contactors, control boards) are final sale once installed
- Email info@nationalhvacparts.com to initiate a return
- Refunds processed within 5-7 business days