What Is a Secondary Heat Exchanger on a High-Efficiency Furnace?
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BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning provides comprehensive furnace service across Greater Vancouver, including diagnostic inspections, emergency repairs, scheduled maintenance, and system replacement. Our Red Seal certified technicians service all major brands and carry OEM parts in their vehicles. For emergency service related to this question, call (604) 330-3953.
Answer: What Is a Secondary Heat Exchanger on a High-Efficiency Furnace?
The secondary heat exchanger is a component found only in high-efficiency condensing furnaces (92%+ AFUE). It captures additional heat from the exhaust gases that would otherwise be wasted up the chimney. After the primary heat exchanger extracts the first round of heat, the exhaust gases pass through the secondary heat exchanger, where they cool further and water vapour condenses — releasing latent heat energy. The condensation process is how condensing furnaces achieve their high efficiency ratings. The secondary heat exchanger is typically made of stainless steel to resist corrosion from the acidic condensate. If the secondary heat exchanger fails (from corrosion or thermal stress), the furnace loses efficiency and may leak water. Replacement costs $800-1,500.
Safety Reminder
If you smell gas, suspect carbon monoxide or believe there is an immediate danger, leave the property and contact emergency services or the appropriate gas emergency authority. Do not remain inside — exit the building immediately and call for help from outside.