How to replace an HVAC air filter

Years ago I got an offer for a job as an environmental geologist in Southeast Michigan, I was very excited for my first career level job and a chance to move away from home. I found an affordable apartment close to the office and in a historic neighborhood. Needless to say I was very excited and moved in in the spring. The spring turned to summer, then to fall and as the temps fell outside they also fell inside my apartment, I thought it was just because the apartment was in an old house and certainly it lacked insulation. Then as winter settled in my apartment would never get warmer that 55 degrees fahrenheit even though the thermostat was set to 70. I decided to investigate and in the basement I found a modern forced air furnace, a clogged filter, and old unsealed ductwork. That day I went to the local home improvement store, bought a new filter, and a roll of duct tape and got to work. After changing the furnace filter and sealing all the duct work I returned to my apartment and to my pleasant surprise it was a nice comfortable, almost too warm 72. Regularly replacing your HVAC filter is an easy task that saves on energy bills, and improves indoor air quality.

Do you have an HVAC air filter and why change them?

HVAC filters are air filters that are placed before the furnace or air handler on a ducted forced air HVAC system. they are there to filter the air before it runs through the HVAC equipment. This serves two purposes, first it keeps dust from building up on the surfaces of the HVAC system that either heat or cool the air, this keeps the system running efficiently. Second is that it helps maintain indoor air quality by filtering dust and other particulates. As filters age the filter pores fill with contaminants and air flow through the filter decreases increasing the energy needed to keep pulling air through the system. In addition they become less efficient at removing indoor air contaminants. Fortunately replacing these filters is a simple and inexpensive task.

How do I know how what filter I need?

If this is your first time replacing your filter(s) you will fist need to locate them in order to get a count of the filters needed and to get the size(s). They are often located on your furnace or air handler. These are large boxy looking pieces of equipment with large ducts going into and out of them. They are usually located in mechanical spaces such as a closet, basement, crawlspace, or attic. Filters may also be located behind one or more large centralized return air grates common in small homes or apartments.

Once you have determined the filter location(s) now you need to determine the size(s), if you have the manual(s) refer to those for the filter size. Otherwise the old filter is usually the same size as the one you will need. Before removing the old filer be sure to turn the HVAC system off, most furnaces and air handlers will have a switch on the side to turn off the unit, otherwise it can be done at the breaker box. Once the system has been turned off remove any filter covers and remove the old filter, its size should be printed on the side. Sometimes filter(s) of an incorrect size will be used if an old filter is too big or too small you will need to measure the filter slot to get the correct size.

Once you have determined the filter quantity and size(s), its time to purchase a new air filter, these can be bought at most home improvement stores. When purchasing a new filter you will see a host of numbers indicating what a filter will filter out. These are called MERV or Minimum Efficiency Reporting Value, the higher the number the finer the particulates it will filter. It may be tempting to buy a very high MERV rated filter, however these don't flow air as well as their lower rated counter parts especially in thin 1 inch filters. A MERV 8 filter is a good middle ground. Its usually a good idea to buy a couple filters at once, store extra filters in their original packaging in a safe spot.

Supplies

• Flat and philips head screwdriver
• Flashlight
• New filter

Steps

1. Before changing the filter, make sure the HVAC system has been turned off.
2. Remove any filter covers.
3. Remove the old filter.
4. Remove the packaging from the new filter, on a visible edge of the filter write the date that it was installed.
5. Install the new filter, make sure that the air flow arrow is pointed in the correct direction. If installing into a furnace or air handler the arrow should point toward the unit. If installing into a return grill, the arrow should point into the duct.
6. Reinstall any grills or covers.
7. Turn the HVAC system back on.