How to change a Furnace Filter

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How to change a Furnace Filter
                            Furnace filter replacement

All air handling units have a filter whether fueled by oil, gas or other process (including air conditioners). Be sure that the filter purchased is the right size (length width and height), and the right quality for your furnace.

Furnace filters help with the efficiency of running the unit which can not only help save money, but also the longevity of the furnace, such that particles and debris do not to accumulate on the system’s motors, blowers and heat exchangers (potential fire hazard) or so clogged it can become a carbon monoxide hazard.

Energy.gov – citing a government study has found “Replacing a dirty, clogged filter with a clean one can lower your air conditioner’s energy consumption by 5% to 15%.”.

Metal or Fabric Furnace Filters?

Usually most furnaces and air handling units have disposable fabric pleated or plastic filters they may have a bit of metal on them but are certainly not all metal.

Some furnaces however have all metal filters which are reusable after cleaning and are replaced approximately every 6 years. They must be vacuumed as well as the chamber or housing they were in once per month as well as the filter to be soaked and thoroughly washed and then reinserted once dry into the unit.

The all metal furnace filters are not very efficient at trapping small particles which are generally the most harmful which is why we don’t see them as much as the disposable filters. However, paired with an add-on filtration system then there is no need to change the whole furnace to get better air quality necessarily. This is a great question to ask our technicians if one is looking to explore their options.

Electrostatic air filters on the other hand are excellent units and require a metal filter however they do an excellent job of keeping dust to a minimum in a home. This is an alternate form of technology to be discussed another day or feel free ask our technicians.

Do I have to turn off my furnace to change the filter?

To change the furnace filter, turn the thermostat to the “off” setting in order to turn off the furnace to prevent the HVAC from turning on while the filter is being changed. Be sure to turn the thermostat back to the previous setting once the filter has been replaced.

Can You Run the Furnace without a Filter?

Firstly, a furnace is designed to run with a filter. Without it, dust and contaminates will accumulate inside the heating inner chamber and could start a fire, or get lodged inside other mechanisms.

How often should a furnace filter be replaced?

The general guideline is:

1-2 inch filters change every three months

4 inch filters change every six months

5 inch filters change every 12 months.

Having mentioned the above, if you have many people living in your space more than the average household, or many furry pets, or people with a delicate disposition such as immune or asthma or other condition, then replacing the furnace filter more often is ideal.

It seems like a simple thing, however consider that hospitals change and filter their air up to 60 times per hour in some sections such as the surgery theatre or burn ward. Thus it goes without saying cleaner air is healthier. (They use HEPA quality filters and additional air purification systems – which a version of this can actually be added on to a residential application).

Signs the air filter needs changed:

A visibly dirty filter needs replacing, and if one can’t see the material of the filter itself, it should immediately be replaced.

Where is the furnace filter located?

The furnace filter is typically located inside of the blower compartment or near the cold air return duct by the filter. There may be a furnace housing access panel, aka a “door” that the filter is behind.

Which way to put in a furnace filter?

Remove the old air filter, this is a good but not perfect indication of how the filter should be placed. Always double check the arrow on the filter that indicates the proper air flow direction. The arrow should face toward the furnace and away from the return duct that carries the air that is yet to be heated or cooled.

For most furnaces, the air filter slides in with the arrow pointing toward the furnace.  Be sure to consult your manual, the website of the brand of furnace or the installation company to be sure.

Some find it handy to draw the arrow on the external furnace housing or duct work to the airflow direct to help aid in the airflow direction, in addition to the filter size.

What happens if you put a furnace filter in backwards?

Be sure to install the filter the right way up as a filter that is installed backwards will put an unnecessary strain on the air handler to make up for the loss of airflow and have a harder time flowing the air through. Not only could it result in higher utility bills, but could potentially damage the furnace or air conditioner.

Can I vacuum the furnace filter?

In a pinch, vacuuming the disposable filter is better than not changing it, however not only could it tear or rip, but a vacuum filter could, once re-inserted, release dislodged but not vacuumed dust and other toxins into the duct work. Not to mention the potential of breathing in these microbes and particles while vacuuming.

Having said that, if your furnace filter is fully metal it is to be checked and washed once per month, and vacuuming it prior to washing..

Can I cut air filter to fit?

No, not a standard filter, the cardboard housing needs to stay intact. However companies such as NaturalAire have a special cut to fit air filter, which requires no frame for support.

Why does my furnace have two filters?

Typically a residential home typically 1 air handling filter – which is a shared Air Handling Unit between the furnace and the air conditioner. However, as thing go, some homeowners discover they have two filters. They serve the same purpose, to filter the air, however each unit, aka the air con and the furnace are on separate filtering circuits. They are generally serviced the same way in most applications.

What is the best furnace filter?

There is a difference in the quality of filters. The ones on this site we have handpicked to be of good and excellent quality that we use ourselves in our daily servicing of HVAC systems. In general the pricier filters are of better quality.

Air filter monitors

Some people find it handy and opt for an electronic air filter monitor, which eliminates guesswork and makes a notification of when the filter needs to be changed, such as clean alert or other brands.

Quick Overview:

  1. Remove any overwrap plastic from the furnace filter—don’t remove the cardboard framing.
  2. Find the airflow arrow and point it toward the furnace
  3. Insert the filter into the slot
  4. Replace any cover or housing of the furnace that was removed when locating the filter.

BTW there are 42K live dust mites in one ounce of dust, on average. 🙂 (consider going with the better quality filter)