HeatingRust on a Furnace: What It Means

If you own a furnace, you may be surprised to learn that this unit can actually develop rust over time. Rust forms when iron reacts with oxygen and water, but a furnace doesn’t use any water to operate, right? While this problem may seem to be more common with a hot water heating system like a boiler, corrosion can actually happen with older furnaces as well. Homeowners are surprised to learn that their furnace has developed corrosion on the flue, heat exchanger, or elsewhere in the system, and this can actually be due to a few separate factors.

The heat combustion process that takes place in a chamber in your furnace produces gases that must be vented outdoors so that they do not form a health hazard when gathering in the house. The gases that form as a result of this process can actually contain corrosive elements. Water vapor and oxygen can interact with the inside of the flue pipe used to vent gases and cause rust to develop, so this pipe may need to be replaced from time to time. Similarly, condensation can occur as the flue passages cool down when the furnace cycles off and form iron oxide.

Rust on the furnace may also be caused by condensation dripping from an improperly installed air conditioner or even from moisture in the air. If your ducts are not properly sealed, moisture may move into the ducts and collect as condensation along the furnace.

In general, if you notice rust on the furnace itself, it means your unit most likely requires replacement. Rust and corrosion are just too big of a risk for your furnace, as they can cause gases to leak into your home if the corrosion causes a serious enough leak. In any case, a rusty furnace is probably several years old, and could benefit from replacement either way. New furnaces are far more efficient than older ones, particularly if you choose one with a high AFUE (annual fuel utilization efficiency), and your new installation may have advanced power and safety features that cannot be beat.

Call G&S Heating, Cooling & Electrical, Inc. to learn more about what rust means for your furnace and how you can schedule heating repairs or replacement in Marysville with an expert technician.


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