Why Is My Furnace Rusted?

December 14, 2021
Furnace Rust in Roseville, MI

Your furnace is the heart of your home. What happens if it stops working? You could suffer severe damage to your property or even a fire. Even if you have a good furnace, rusting can still be a problem that affects your furnace’s performance. It’s best to know what causes it and how to deal with this condition before disaster strikes. Here are some tips to help you shed light on the potential problem.

What Is Rust, and What Causes It?

Rust is a kind of oxidation. It turns ordinary iron into iron oxide, also known as “rust.” If you have rust, it means that something has caused the iron to oxidize. The most common cause is condensation or water damage that has created cracks in the furnace’s area.

Rusting is the corrosion of iron and steel. The process causes the metal to break down at the atomic level, leaving red or brown dust covering the furnace. With time, rust leads to a weakening of the furnace’s metal structure and can also cause leaks.

If rust is a problem in your furnace, it’s a sign that you need to service or replace it. Here are some of the factors that may cause rusting on your furnace.

Moisture and Humidity

Humidity and moisture are the biggest culprits of rust in furnaces. Humid air carries water droplets suspended in it. When this humid air is pulled through a furnace, the water droplets get heated up and evaporate. The water contained in these droplets condenses on cold surfaces, which can include your furnace’s internal components. This condensation can cause rusty spots to form on heat exchangers, burners, and other furnace areas.

So why does a furnace produce rust? Because it’s made of metal, and many types of metals oxidize when exposed to air or water. The process is called oxidation or corrosion. Corrosion means that one substance–the air in this case–chemically changes another substance, which is the metal. In this case, oxygen from the air chemically changes the metal in your furnace. The combination of humidity and oxygen can cause your furnace to rust very quickly if not properly cared for and protected.

Leakage in the Air Conditioner

If the furnace has some rust in it, it’s an indication that there could be some leaks somewhere in the system. In most homes with central heating and air conditioning, the air conditioning unit is installed on the furnace. Air conditioners produce condensation, which drains into a condensate pan. Water will overflow and drip onto the furnace if the drain becomes clogged. As a result, both are potentially vulnerable to rusting.

Faulty Furnace Exhaust

If you have a “rusty” looking flue coming from your furnace, this may be caused by several things. Processing the exhaust from the furnace is supposed to be precise. When the furnace is running, the heat and moisture in the exhaust should keep it from rusting. The lack of heat or moisture can cause a flue to rust. It will eventually rust out if a flue is constantly wet from condensation.

If you have a faulty exhaust system, water vapor can be pulled back into the furnace through its intake pipe, which directs cold air from outside the house to make a counter-current flow with warm air going out. It causes condensation within the system and rust buildup inside the unit.

The most common cause of a rusted flue is incorrect installation. If a flue is improperly installed, there may not be enough clearance between the pipe’s inner wall and the chimney’s outer wall or venting pipe. Moisture collects on the inside of the pipe wall causing rusting on the outer surface. A similar problem can occur if an expansion joint is not used with a right-angle bend in the flue run.

Other causes include clogged dampers and water leaks around windows or doors that drain directly into or near the exhaust pipe resulting in excessive moisture entering the pipe.

What Can Be Done If Your Furnace Is Rusty?

If you have a rusty furnace, the first thing you should do is to ensure that all your filters are clean. Your furnace functions on airflow, and if there’s dust in the way, it will not function properly.

You can also remove all the dust and grime from your furnace. It’s an easy job for homeowners. However, it’s vital to ensure that your filters are clean before cleaning your furnace. Then, you can use a vacuum cleaner to clean the vent ducts where the air flows into the home. The best time to do this job is in late winter or early spring when it’s not too cold.

A great way to prevent dirt from getting back into your ductwork is to keep your ducts free of obstructions. If you find debris in your ducts, consider hiring a professional to come out and clear out your ductwork.

Rust can become a functional problem when it’s allowed to continue. It only takes a few days for rust to form in damp or humid conditions, so it is important to act fast when you notice any signs of rust developing on your furnace.

The first thing that you should do is make sure that there are no cracks in the furnace. Cracks are a common cause of rust and are the easiest thing to take care of. Get a flashlight and shine it through all openings, looking for cracks. If you find any cracks, have them repaired right away.

You can repair small cracks with a metal repair kit from the hardware store, but if the crack is large or if you notice other damage to the furnace, contact us at C & C Heating & Air Conditioning.

Our technicians at C & C Heating & Air Conditioning provide services to clean your furnace and remove the rust. Once this is done, you need to insulate your pipes and ducts to prevent any future rusting.

The best way to do this is by using metal tape. Metal tape comes in different widths, but one that is two-inches wide should be enough to cover all of your pipes and ducts. To cover all of them, you will have to overlap the pieces of tape. You can then paint over the tape or leave it as is, depending on how good you want it to look.

A second option for covering your pipes is fiberglass insulation. It works well because it provides additional heat protection for your home and protects the pipes from rusting again in the future. You can install this insulation easily by wrapping it around each pipe separately. This project may take some time, but it’s worth doing to ensure that your furnace will continue working effectively for years to come.

Knowing why you have rust in your furnace is the first step to making an informed decision to fix or replace it. A dialogue with professionals at C & C Heating & Air Conditioning is the second step. We offer duct cleaning and repair services, furnace and AC installation, furnace and AC maintenance, and other cooling and heating services to all of our neighbors in the Detroit metropolitan area. Contact C & C Heating & Air Conditioning in Roseville, MI, for more information.

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