Rust in Your Furnace? Here’s what you need to know

Rust in Your Furnace? Here's what you need to knowYour furnace doesn’t use water to operate like a boiler, and there aren’t any water leaks in the area – so why is it rusty? A rusting furnace can seem strange, but it could point to a larger problem. It’s one of the things an experienced, professional heating repair company will look for when performing maintenance and repairs. If you see rust on your furnace, you shouldn’t run it until it has undergone a professional inspection and earned a clean bill of health.

What Rust on Your Furnace Could Mean

  • Surface rust
    While external rust from a nearby moisture source may not be a major problem, it could indicate serious internal issues. Even if you only see rust on the surface of your furnace, avoid using your system until safe operation is verified by an experienced HVAC professional.
  • Rust on the heat exchanger
    Rust on the heat exchanger, an internal system component, often goes unseen by the typical homeowner. This is why annual preventative furnace maintenance is crucial. When spots of rust appear on the heat exchanger, it points to the potential risk of the heat exchanger cracking. A rusted, cracked heat exchanger should be replaced or repaired  immediately to avoid the possibility of toxic, potentially deadly combustion gases like carbon monoxide from infiltrating into your home.
  • Clogged or blocked condensate line or flue
    When exhaust and drain lines are blocked, the small amount of fluid present as part of gas combustion are not properly transported away, creating a greater likelihood of moisture exposure and corrosion within the system (such as the aforementioned heat exchanger).
  • Old age
    Long years of use can cause corrosion from extensive exposure to combustion, making old systems more likely to showcase rust on the heat exchanger. In furnaces more than 15 years old, furnace replacement is a wiser investment than repair. These systems may offer only 60-80% efficiency, compared to newer Energy Star systems boasting performance near 97%, ensuring a rapid return-on-investment and a more comfortable home climate.

How Does Rust Occur if There’s No Water in the System?

There is some water vapor present in the combustion gas collected in your furnace’s heat exchanger. As these gases cool, water vapor can develop. In high-efficiency condensing furnaces, this water vapor moves to a second heat exchanger, where it is condensed, releasing more heat. This is how the metal of the heat exchanger is exposed to water, causing rusting. However, with proper operation, this moisture should be vented out via the condensate line and flue.

Rust on your furnace? Schedule emergency service and repair right away. We offer 24/7 service at no additional cost to you, so you can rest assured of safe furnace operation. Contact H & H Heating & Air Conditioning to schedule service and maintenance now.

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