Water droplets on metal - Why Is Moisture a Concern with Furnaces?

When moisture comes in contact with metal, it can lead to corrosion, which in turn weakens the metal and eventually causes it to crumble into nothing. In essence, when it comes to metal appliances in your home, corrosion is enemy #1. But how does this apply to a furnace?

Unlike a boiler, which circulates water as part of its operation, a furnace does not use water to work. Therefore, it may seem strange that a furnace might rust because of moisture unless there was a flood where the furnace cabinet is located. However, furnaces can and do rust because of moisture exposure; no flooding necessary. Here, we’ll go over why you may encounter moisture concerns with your furnace.

Furnaces & Moisture Concerns

Moisture can occur inside your furnace from three different sources. The first is from dampness that can enter through the ductwork from outside. This is most often a problem when the ducts develop leaks that let in external air.

The second source is from trouble with your air conditioner. Usually, an air conditioner sits directly above the furnace unit. If the air conditioner’s condensate pan drain becomes plugged, the water collected from the condensing coil will start to overflow and drip out. If this water gets into the furnace, it will rapidly promote rust. The moment you notice water dripping from the bottom of your furnace, you need to call for both heating and air conditioning repair.

The third source comes from poor exhaust venting inside the furnace. When the combustion products inside the heat exchangers of a furnace cool down, they turn into liquid water vapour. That’s right; your furnace produces water. The reaction between this exhaust vapour and the heat exchangers will eventually cause corrosion; however, the exhaust quickly vents outside through a flue. If this venting becomes inefficient, it will speed up the corrosive action between the combustion products and the metal. A corroded heat exchanger is potentially very dangerous since any cracking will permit the escape of carbon monoxide into the cabinet.

Do You Need to Replace a Rusty Furnace?

Unfortunately, corrosion on a furnace is often a sign that the system is coming to the end of its service lifetime. If your furnace is over 20 years old and it begins to rust, you should probably schedule a replacement installation before a full breakdown occurs.

Call the Experienced Technicians at Advantage Airtech

Advantage Airtech has brought quality heating and air conditioning to the Greater Toronto Area since 1987. When you need help with your furnace in Markham, ON, whether it’s corrosion or any other repair need, make us your first call.

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