How Does A Furnace Work? Learning How To Keep Your Furnace Working


There is nothing more comfortable and relaxing in your warm home while the furnace works and snowflakes cover the ground. You look outside and you can imagine the freezing temperature, but you are happy your gas furnace works and the heat exchanger keeps you warm. It makes no difference if you rely on a classic gas furnace or you run a classic air conditioning (HVAC system) unit.

Now, most people never bother to figure out how their furnaces work. As long as the warm air kicks in and the air quality is high, they are happy. However, knowing how this unit works will help you prevent potential problems. You will also figure out how to keep it running or when to replace it should such problems arise. So, how does a furnace work?


Classic Heating Cycle On A Gas Furnace Explained – How Does A Furnace Work?

Most furnaces rely on the same operating principles to heat the air in your home. The unit usually comes with a combustion chamber where natural gas or propane is sent to. It is then ignited in the burner. Flames gain in size and target the metallic heat exchanger. At the same time, you need the harmful exhausts out of the house – a proper installation will ensure you do not get intoxicated.

The heat exchanger will take the heat over and push it into the warm air. The furnace also has its own blower, which will push the heated air into the ducts. Assuming the vents are open, the warm air will be sent throughout the home. On the same note, the system will also have return ducts. The cold air – which is also denser – will be sent to the furnace through these ducts. It will warm up before being sent to your rooms again.

It is a matter of minutes until the indoor air and the air temperature go up.

Now, how does a furnace system work? There are more parts in a furnace that work together in a tight collaboration to keep the hot air going around your home.


furnace gas


Parts Of A Heating System Explained – The Importance Of A Good Heat Exchanger

The thermostat is the most common and basic part in a heating system. It is practically a switch that is activated by the temperature of the room where it stays. It has a certain value that you can set yourself. When the temperature drops under that limit, it gets the furnace to work.

The thermostat begins the ignition and heats the home until the desired temperature reaches your limit. Keep in mind that the thermostat only “cares” about the temperature where it is located, rather than the whole house.

Second, you have a fan that makes the process smoother and more efficient. Air goes into burners. When mixed with gas, it stimulates the combustion. A fan can help make this process fuel efficient. However, this is only a plus.

The primary role of the fan is to send the forced air into a heat exchanger. Exhaust gases (which are extremely harmful) are sent outside of your home through this unit.

You might be familiar with burners though. They work just like the burners on your gas grill. These parts are practically some tubes that direct gas towards its burning point. Of course, there are more parts involved in the process, such as a gas valve, a flame sensor and an igniter.

When the system requires more heat, the valve will open up. Gas and air come together and the result is ignited. The sensor has a safety role, as it shuts off further gas if it detects a flame. It is no longer needed, so it can prevent gas accumulations.

The heat exchanger is an amalgam of metallic tubes. They receive heat from the burners and they are directly responsible for warming up the air. Gas hits the heat exchanger, while the metallic tubes go hot. The heat will be pushed into the air that passes through.

The heat exchanger is one of the most important parts in a furnace. Apart from dealing with heat air, it also protects against gas leaks into the house. Damage to this part can endanger you and your family. Some modern or more expensive furnaces may come with extra heat exchangers and unique curves to ensure the heat transfer rate is kept under control.

The blower is self explanatory and directs air into the heat exchanger. The warm air is then sent into the ductwork – and your home. Some furnaces come with preset blowers, while modern blowers feature variable speeds that adjust by themselves based on how intense the operation is.

Last, but not least, do not overlook the flu. This is a vent that will grab all the combustion gases before taking them outside of your environment. Most of these vents are based on galvanized steel for an average efficiency. High efficiency – and more expensive – units rely on polypropylene vents.

Frequently Asked Questions

Still unsure of how your furnace works? Here are some common questions you may have in mind.


How do you tell if the furnace is working?

You’re burner malfunctions if you can sense unusual smells coming from the ductwork. For example, burning odors might underline a problem. It is alright to feel a dusty smell every now and then though. Other than that, soot, rust or dirt could be an issue too. If you can see the flame, take a look at it when the burner works – it must be blue. Unless you are a professional working in this field, you should simply turn the unit off and seek help from a technician.


How long does a furnace work?

It depends on more factors, such as the brand, materials, quality standards and so on. Your overall care is just as important. Generally speaking, a traditional gas furnace should last anywhere between 15 and 25 years. Some units can last up to 35 years, but these cases are rare. All in all, assuming you take care of the annual maintenance recommended by the manufacturer, your furnace should easily keep going for more than 15 years.


Are furnaces dangerous?

Furnaces represent the main cause of death when it comes to carbon monoxide gas. The gas has no scent, so it cannot be detected. It kills hundreds of people a year. A well maintained and high quality working furnace is less likely to cause this issue, but a defective one could. Make sure you schedule the required maintenance operations whenever they are needed.


What is furnace and its function?

A furnace – sometimes referred to as a boiler or a heater – is used to keep your home warm. It will provide heating throughout your home, but it will also ensure you have hot water when you need it.


Bottom line, how does a furnace work? The operating principles are pretty easy to understand. You have gas, a flame and a few parts that push warm air throughout your home. It is one of those appliances you simply cannot leave without in terms of comfort and convenience, so make sure you invest in a quality unit and look after it.

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