Hansberger Refrigeration Blog: Your AC Repair Resource

How to Know if You Need a Stainless Steel Heat Exchanger

At some point in the life cycle of your furnace, you may have to make a choice between a stainless steel heat exchanger as opposed to one made of coated iron. The heat exchanger is the component that transfers heat from gas combustion into the airflow circulating throughout your house. It also serves a very important safety function by keeping dangerous combustion fumes — including deadly carbon monoxide — out of the furnace airflow.

Replacing a cracked or deteriorating heat exchanger is a critical issue. Here are some factors to help you make an informed choice between a coated iron heat exchanger and a stainless steel heat exchanger.


Because the heat exchanger is usually the most expensive single component in a gas furnace, you want one that is long-lasting. A stainless steel heat exchanger actually reacts to heat by forming a protective oxide on the material that prevents moisture-related corrosion and heat damage. An Typical coated iron replacement, conversely, reacts to moisture that’s produced by gas combustion and deposited in the heat exchanger as it cools between cycles. Over time, this moisture triggers corrosion that degrades the coating, shortening the service life of the component.  The coating on an iron heat exchanger is usually a form of aluminum or zinc (galvanized).

Initial Price Versus Long-Term Cost

The upfront sticker price of a coated iron heat exchanger is usually lower than that of a stainless steel heat exchanger. That’s because stainless steel is a material which requires special processing. However, practical cost analysis must include the fact that a coated iron unit is not as durable as a stainless steel heat exchanger. If the coated iron model requires replacement again during the life cycle of the furnace, the upfront cost advantage of the material is negated and the coated iron heat exchanger becomes significantly more expensive.

For professional advice about the choice of a stainless steel heat exchanger versus a ductile iron unit, contact the professionals at Hansberger Refrigeration and Electric Company.