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How Does a Furnace Work?

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Posted December 8, 2020
A hand pulling the filter out of a furnace

Today, we wanted to answer the question that’s no doubt been “burned into” your mind … How does a furnace work?

You know that your furnace is able to supply warm air to your home through ducts and registers, and through changing your thermostat. But what exactly is the magic behind how a furnace works? Well, it’s not magic, it’s science! Here are the basic steps of how a furnace works:

1. Gas is heated in the furnace

Your furnace is powered by propane or natural gas being burned. The way this process starts off is, when you turn your heat on with your thermostat, it activates a control board inside your furnace. This turns on the ignition switch. Ever wondered what that clicking noise is when your furnace turns on? It’s the igniter sparking up and igniting the gas. (However, if your furnace doesn’t make a clicking noise, that doesn’t necessarily mean anything is wrong. Not all igniters use a spark to heat up the gas.)

2. The heat exchanger gets hot

As the gas in the furnace burner heats up, the heat transfers to a group of tubes called a heat exchanger. These are metal, so as they get hot, their heat leaks into the surrounding air. So now you’ve got hot air!

3. The furnace blower blows the air to you

The furnace blower is a fan that is located beneath the igniter area and the burner of your furnace. This fan pushes the hot air into your air ducts, which is how you get nice, hot air on a cold winter’s day!

4. The process starts over again

Next, the blower also draws cold air back into your furnace through the return vents. As you can imagine, the hot air being pushed into your room cools off — and since colder air is denser, that’s what naturally gets drawn back into the ducts. Then, the heat exchanger heats it back up again, and the air is cycled through your home over and over, with your furnace reliably keeping it warm.

5. What if your furnace isn’t reliable?

Of course, if your furnace won’t come on … or it won’t turn off … or it seems to be on but isn’t blowing … or nothing happens when you hear the clicking noise from the igniter … OR you hear odd noises … then something is wrong! You won’t be left out in the cold this winter in Houston, if you call Air Specialist. We can handle any repair. Just call [csad_phone] or contact us online


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