{"product_id":"oem-lennox-heat-exchanger-assembly-21w91","title":"OEM Lennox Heat Exchanger Assembly — 21W91","description":"\u003cp\u003eThe genuine OEM Lennox \u003cstrong\u003e21W91\u003c\/strong\u003e heat exchanger assembly is the primary heat-transfer element in your Lennox gas furnace, drawing heat from the burners into the circulating airstream while keeping combustion byproducts fully separated from the air delivered to your home. Manufactured to original Lennox tolerances, the \u003cstrong\u003e21W91\u003c\/strong\u003e installs as a direct, no-modification replacement in its compatible furnace models.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eCommon failure symptoms:\u003c\/strong\u003e Look for hairline cracks or rust in the metal, a burner flame that lifts or wavers when the blower starts, soot accumulation, odors during heating cycles, carbon-monoxide detector activity, or repeated high-limit trips causing short cycling. These are strong indicators that the exchanger's gas-tight barrier has been compromised.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhy OEM matters:\u003c\/strong\u003e As a safety-critical part exposed to continuous high-temperature expansion and contraction, the heat exchanger depends on precise alloy selection, weld quality, and exact dimensions. The authentic Lennox \u003cstrong\u003e21W91\u003c\/strong\u003e restores factory-certified combustion sealing, correct alignment with burners and controls, and the efficiency and warranty compliance your Lennox system was designed to maintain.\u003c\/p\u003e","brand":"Lennox","offers":[{"title":"Default Title","offer_id":63081071214963,"sku":"LNX-21W91","price":399.95,"currency_code":"USD","in_stock":true}],"url":"https:\/\/nationalhvacparts.com\/products\/oem-lennox-heat-exchanger-assembly-21w91","provider":"National HVAC Parts","version":"1.0","type":"link"}