How to change furnace filter

[pcdoctor]

Hey. I would like to know how often a furnace filter should be changed, what type of filter it takes and how to do it. We moved into a house that has a forced air furnace a little less than a year ago and have never changed the filter. Also, how many filter's does it take?

[Dean]

Some need changing much more often than others, it depends on several factors such as;
How clean the house is
How low are the return air grills
What type of filter
Is the house located near high traffic road or highway where there is a lot of dust.
How dirty do you want it to get before changing it.
The percentage of time that the blower is running. (mine runs 24-7)

Pull the filter out and hold it up to the light to see how much light shines through and while you have it out, check it for the size.

Many people change their filters every couple of months wether it needs changing or not while other folks might only change them once a year or at the biginning of each heating or cooling season.

Once you establish a history of how often yours gets dirty, you will know how often you want to replace it.

[LazyPup]

Normally a residential HVAC system will only have one filter.

It may be located in numerous places.

If you have ducted return air it might be in a slot in the air duct near where it attaches to the furnace or it might be in a slot inside the furnace housing on the intake side of the blower.

If your furnace is installed in a closet with just a return air grille through the wall or the door, the filter may be inside the grille. Look for a couple little thumbscrew knobs on the grille frame. twist the knobs and the grille swings out to expose the filter.

As was mentioned before,,how often to change the filter depends upon how dusty your enviroment. If you live in a dry dusty region, have a long haired pets, or active children tracking in and out constantly you may need to change it more often.

After almost 35 years of working on HVAC systems, i make it a habbit to change mine at least once a month. It only takes about 5 minutes and is very easy to do. That may sound a bit exhorbitant to some, but filters can be purchased over the counter in bulk for about $15 a case of 12 at an HVAC parts house, which means $15 a year..If someone comes and cleans your air conditioner coil your looking at $150+.

If the filter is obstructed it may reduce your unit effieciency to nearly zero and in the case of an air conditioner it could result in iceing the coil and a total system failure,,($3000+)

filters are designed to trap mircofine dust in the air,,,if you can see a layer of dust on the surface of the filter,,change it.

Ask any HVAC tech and he or she will tell you,,dirty filters account for more than 60% of all HVAC service calls.

[Dean]

quote:Originally posted by LazyPup


Ask any HVAC tech and he or she will tell you,,dirty filters account for more than 60% of all HVAC service calls.

That's for sure but don't spread it around, we make a lot of money fixing them.
(just kidding)

Most filters do a better job of removing the finer particles after they get just a little dirty but you don't want them to get plugged bad enough to restrict air flow.

One thing I have always noticed is that most people think the air filter is part of the furnace when usually the filter slot is provided by the installer.

[LazyPup]

Dean,,i sure aint kidding,,i dont mind running 20 calls a day for a $39 service call,,just to change a filter and run to the next one. Most of the HVAC techs I know got rich as a result of dirty filters or the problems associated with them.

When i was in Florida I was maintenance supervisor for a property manager that had 17 apartment communities, a total of 2300 apartments. As a test, on one property we cleaned all the AC coils at season startup, then gave the tenant a new filter each month when they came to pay the rent.We then posted a notice that if we had to repair an AC that failed because of a dirty filter and found a filter over a month old the tenant would be responsible for the labor of the repair.

There were 218 apartments on that property and we had a total of two that needed followup service which could be attributed to dirty filters.

By contrast, the other properties we managed averaged 23% sytem problems attributed to dirty filters in the course of a year.

I might add, that those were all Byrant, Intertherm, Rheem or Ruud, contractor grade units, some of which were original to the propery (1972) and the test was in 1985. Based on that experience the management company put that procedure in place on all properties the next year and their annual HVAC budget is right now less than 1/2 of what it was in 1985 so I will stand by the statement that FILTERS ARE TOO CHEAP NOT TO CHANGE THEM OFTEN.

[Dean]

Yep, for sure. I always wondered why in the heck homeowners let their filters go so long when they are so cheap and most of them so easy to replace.

I bet 99.9% of the "freeze up" or "plugged up evaporator coil" calls we get from rental property are caused by neglected air filters.

[imeduc]

We always tell home owner every 30 to 90 days

ED

My mistakes dont define me they inform me.

[smr]

I am using an Heil DC90. The former filter is a cheapest one put by previous owner. Can I put on a most expensive or efficient one? By the way, the filter size is around15"x24"x1/2"(1"?), is it the right size to tell the hardware store?

[LazyPup]

many people make the mistake of buying the most expensive filters and expecting them to last longer. Filters are graded by microns, which is the diameter of the smallest particle that can go through without being trapped. While the expensive, very low micron filters do trap a considerably larger amount of air borne particulates, in turn, they will actually clog up faster than the cheapies due to the very nature of the design.

While working in Florida one of my duties was to service the filter pack in a hospital 300 ton air handler. The return air filter pack was 12' x 12' and used 144, 1'x 1' x 1' aluminum clad HEPA filters which cost $90 each for a cost of $12,960 plus labor per change. In an effort to curb cost they had installed a hydrostatic differential manometer on the filter pack to accurately measure when the filters required changing. After a year of accurately graphing those filters it was determined that they needed changing every 35 days.

I like to use a simply rule of thumb. You cant see the dust and dirt particles in the air, therefore, if you do see a substantial film of the dust and dirt on the surface of the filter, its time to change the filter. Even the better grade filters are cheaper than a cup of coffee at Starbucks so it still stands, filters are simply too cheap not to change them often.

In my house the rule is, change the filter on the first of the month and that is on aystem that also has an electrostatic scrubber and Ultra-violate sanityzer. The trade off is, my Lady doesnt even own a dust rag and i dont have to worry about coming home to a frozen evaporator coil.