How to maintain your furnace


Furnaces are a necessary, but expensive part of your home. If your furnace breaks down, you could be out a lot of money in repair costs or replacement, so we've compiled a do-it-yourself checklist for home furnace maintenance. If you're willing to invest some time and energy, you can keep your furnace working for years to come.

Step 1: Turn off the fuel supply and power
You definitely don't want to make the mistake of trying to service an active furnace. To turn off power to your furnace, locate the red switch that can commonly be located near the furnace or at the top of your basement stairs, and switch it off. Remember the location of this switch just in case you ever have a fire or some other emergency. Next, you need to find the fuel shutoff valve. If you have an oil-based heating system, this will probably be on or near your oil tank. A gas furnace should have the switch on the incoming gas pipe.

Step 2: Clean the combustion chamber
The combustion chamber is where all the fire happens. According to This Old House, soot that builds up in the chamber can corrode the walls, so you'll need to get it out. They recommend that you use a wire brush to scrape everything off the walls before getting a vacuum in to scoop up all of the loose soot in there. While you're at it, look for corrosion that's already occurred – particularly holes. If you find significant corrosion, you'll need a professional to service your furnace.

Step 3: Inspect the flue pipe
The flue pipe is the large pipe leading away from your furnace – it carries out smoke and other chemicals that result from combusting gas or oil. Check the pipe for holes – a small hole can be patched up using foil tape say the experts at This Old House, but a larger hole caused by corrosion takes a professional. While you're at it, you should consider getting a pro in to adjust the pipe anyway. Often flue pipes' barometric dampers start pulling too much air through, resulting in an inefficient furnace. A servicing professional can weigh the damper, which will improve the efficiency and lifetime of your unit.

Step 4: Replace the oil filter
If you have an oil-based heating system, your oil filter removes the tiny impurities in the oil that can clog up your system. After a while, your filter will be all used up and you'll need a replacement. To do this, simply close the oil valve and pull out the filter. Once you've replaced your oil filter, remember that you can't just throw the old one out. Used oil filters count as hazardous waste, so they need to be disposed of appropriately – just like batteries. How Stuff Works recommends that you change your oil filter at least once or twice each heating season, depending on use, so you'll have to use a bit of judgment to figure out when to change yours.

Step 5: Change the air filter
Both oil and gas burning furnaces have an air filter, and all of the air you and your family are breathing throughout the winter passes through this filter. After a while, a filter will get dusty, which not only reduces efficiency, but also isn't good for your lungs. Luckily, an air filter is easy to change – just pull it out and put the new one in. You should replace your air filter every three months, according to, and definitely don't let it go for longer than a year.

This Old House recommends that you also check out the blower belt while you're in there. The blower belt moves the fan that pulls all of the air through your system, and over time this belt can become loose – making the system less efficient. It's pretty easy to check whether your blower belt is too loose – just press down with your finger. If it moves by more than three-fourths of an inch, you need to slide the motor back slightly in order to put more pressure on.

Step 6: Inspect your ducts
Once you've finished with your furnace maintenance, it's time to inspect the ducts that carry your heat throughout your house. Even a small hole in one of your ducts can cost you a lot in heat, so make sure you patch them up with foil tape. If your ducts are passing through a lot of unheated space – like a basement – consider adding some insulation to make them more efficient.

If you're worried about the potential cost of replacing your furnace, consider purchasing a home warranty. A home warranty can save you from unexpected expenses by reducing your risk to a low, monthly payment, saving you money and giving you piece of mind.

The information in this article is intended to provide guidance on the proper maintenance and care of systems and appliances in the home. Not all of the topics mentioned are covered by our home warranty or maintenance plans. Please review your home warranty contract carefully to understand your coverage.