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How a Sealed Combustion Furnace Works

furnace flames

The HVAC technician boasts that this particular furnace model has a 90% AFUE with a “sealed combustion chamber” You nod as though you understand, but you have no idea what he’s talking about.

That’s understandable. For the uninitiated, furnace technology can be complicated.

Let’s break down what sealed combustion means in laymen’s terms.

Sealed Combustion Explained

Your conventional residential furnace has atmospheric combustion. That means the unit draws in air from inside your home to fuel the combustion process -- basically mixing air with the gas from the burners. What it doesn’t use for heat it exhausts to the outside through the flue vent.

A furnace with sealed combustion takes a different approach. It draws in air from outside through an inlet pipe. The combustion chamber, where all the burning action occurs, is sealed off from the rest of the house.

Why Sealed Combustion is Better

Sealed combustion is more efficient because it’s not removing already-heated air from inside your home to keep the burners burning. It’s using a fresh source of outside air. This comes with several benefits:

  • Higher AFUE: Any furnace with sealed combustion will have an AFUE of at least 90%. That’s the annual fuel utilization efficiency rating. The more fuel the furnace converts to heat the higher its AFUE. A heating system with an AFUE of 90% means only 10% is wasted in the combustion process. That means improved comfort and a lower energy bill. In contrast, most conventional furnaces will have an AFUE of 80%.
  • Improved air quality: A sealed combustion furnace isn’t recirculating the same air. It’s pulling in fresh, clean air from outside and converting it into heat energy. In contrast, an atmospheric system will draw in stagnant air for the heating process. This is especially a problem if the unit is located in, say, the laundry room. It’ll utilize air filled with chlorine and other household chemicals and distribute polluted air throughout your home -- not great.

Bottom line: If your current furnace is on its last leg, consider replacing it with a high-efficiency furnace with sealed combustion. You’ll slash your energy bills and improve your comfort. For an expert installation, turn to the pros at Gillece Services by calling (412) 831-6199.