OEM Lennox Stainless Steel Heat Exchanger — 19A78

The genuine OEM Lennox 19A78 is a stainless steel heat exchanger assembly built for long-life, corrosion-resistant performance in your Lennox gas furnace. As combustion gases flow through the sealed internal passages, your blower pushes household air across the exterior — the exchanger transfers that heat into your home while keeping flue gases completely isolated from the air you breathe. Stainless construction resists the acidic condensate that forms in high-efficiency and secondary heat transfer applications.

Common failure symptoms: watch for a distorted or flickering burner flame, rust or scale flaking into the burner box, a burnt or metallic smell during operation, unexplained carbon monoxide alarms, or repeated flame-rollout or limit-switch trips. A visibly cracked, warped, or perforated exchanger should be taken out of service right away because of the CO risk.

Why OEM matters: the 19A78 is dimensioned to your furnace's exact burner count, gas input rating, and cabinet layout. A genuine Lennox exchanger restores factory heat rise and combustion safety, keeps your equipment listing and warranty valid, and ensures a bolt-in fit — generic replacements risk airflow and combustion mismatches that shorten furnace life.