Quantcast How to Replace a Furnace Filter – DIY House Tips

How to Replace a Furnace Filter

By on January 7, 2010
How to Replace a Furnace Filter

If you have a forced air heating system you should periodically replace its furnace filter. You may be asking yourself, “What does he mean by a forced air heating system?” To determine if this is the type of system that heats, and possibly cools your home, first take a look around each room in the house. Do you see “grills” that cover holes in the floors or walls? How about around your furnace, do you see metal duct-work that leaves the furnace and goes off to different parts of the house? If the answer to both of these questions is yes, then you have a forced air heating system. In this type of system, a blower sucks cool air into the furnace, blows it past the burner into a heat exchanger where it gets hot, and out through the duct-work where it is distributed to all the rooms in your house. Some of the registers (grills covering the holes) are the ends of the ducts where heat enters the room. Other registers are called “returns.” These registers are where cool air returns to the furnace.

What Filters Do for the System

Filters play a very important part of any forced air heating system. They are partially responsible for the efficiency and longevity of the furnace. You will find the filter where the cool air is entering the furnace. Its purpose is to keep dust, dirt, hair, and other particles from entering. A dirty filter makes it harder for the furnace to pull air in and through the duct-work. Replacing the filter on a regular basis keeps the air flowing smoothly so you will increase the furnace’s efficiency and reduce your fuel bill. You will also prolong the furnaces useful life because it doesn’t have to work as hard, reducing the chance of costly repairs or replacement.

When to Replace Your Filter

So, what kind of filter do you need and how often should it be changed? First of all, the general rule of thumb is your filter should be changed every 3 months. This could vary depending on any unusual conditions. For example, your spouse has a wood shop in the basement that creates excessive dust and dirt. It can also vary due to health reasons such as allergies. In either case you would want to replace the filter a little more frequently.

Choosing a Filter

“There are so many different kinds of filters. Which one should I buy?” I suggest you stick with the least expensive. Surprised? Let me explain. Filters are rated by what’s called the MERV rating system. It stands for Minimum Efficiency Reporting Value. Basic filters will have a MERV rating of 1 to 4. These filters are typically made of fiberglass and stop particles of 10 microns or more which is perfectly sufficient to keep your furnace safe from any damage. Filters with MERV ratings of 5 or more such as electrostatic, pleated, or HEPA, keep smaller particles from circulating throughout your house. They are helpful if you suffer from allergies, but essentially you’re turning your heating system into an air purifier. They make your furnace work a lot harder and shorten its lifespan. The better solution for allergy sufferers is to replace the filter once a month and buy a standalone air purifier. It’s a lot cheaper than buying a new furnace.

Replacing the Filter

When you go to replace the filter, first switch the furnace off, locate the old filter and pull it out so you can determine the correct size. This is important because the filter should fit snug without any gaps where debris could pass through. You can search for your replacement filter here in the home improvement store, or find one at most hardware stores and home centers.  Low end filters will run $1.50 to $2.00 and high end like HEPA are around $15.00. But again, unless you are replacing the filter in a hospital, you shouldn’t need such extravagance. Once you’ve purchased your new filter just swap it out with the old one and turn your furnace back on.

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