Questions & answers about the location of heating or air conditioning or heating system filters.

HVAC air filter location, placement, or similar problem questions & answers are discussed here.

This article series explains in detail how to find the air filters on an air conditioning or hot air heating system.

FAQs on Where & How to Find the Air Conditioner or Furnace Filter

If you can't find your air conditioner system filters (there may be more than one air filter) some places to look are given at .

The questions & answers below about where to locate the air filter in air conditioning, heat pump, or forced-air heating systems were posted originally at AIR FILTER LOCATION

On 2018-08-07 by (mod) -

Mario,

The air filter location on a heating or air conditioning system is not absolutely-fixed. The air filter is often right at the air handler unit or "blower unit" but it could located with equal probability elsewhere in the building such as at the air inlet grille of a central air return.

The article above - this page - includes suggestions for finding the air filter on your system.

In essence, follow the air flow.

Start by identifying the air return inlet - there will be one or more. If there is no filter there, find the air return duct connection to the air handler. Look there.

If there is no filter at the air return plenum where the return air duct connects to your air handler, then the air filter is likely to be inside the air handler: there will be a door or handle that can be turned or lifted to open the air handler

Watch out: TURN ELECTRICAL POWER OFF FIRST to AVOID INJURY

In the article above try reading the section titled

A Detailed Guide on How to Find the Air Filters on an Air Conditioning or Heating System

Here is an excerpt from a typical Goodman Air COnditioner manual found at https://inspectapedia.com/heat/Goodman-AVPTC-14-Air-Handler-Manual.pdf

10 Return Air Filters

Each installation must include a return air filter. This filtering may be performed at the air handler using the factory filter
rails or externally such as a return air filter grille. When using the factory filter rails, a nominal 16x20x1”, 20x20x1” or
24x20x1” (actual dimension must be less than 23-½”x20”) filter can be installed on a B, C and D cabinet respectively (the cabinet size is the seventh letter of the model number).

If you don't have the manual for your Goodman air conditioner see GOODMAN HVAC free manual downloads at https://inspectapedia.com/heat/HVAC-Manuals-Air-Conditioners-Boiler-Furnaces-F-I.php#Goodman

Below is an image of a current Goodman air handler. The front lower door can be removed by sliding up and lifting it out.

On 2018-08-07 by Mario

I have a Goodman where is the filter located

On 2017-11-10 by Tommy p

my HAVAC has TEN, yes I said 10 return air filters.there are 2(12x12) in each bedroom, top and bottom grills and 2(16x16) in the main trunk(these are located in the family room).
I use a merv 8 and when I check them after three months they hardly have any dust or dirt on them, so I change them again anyway. why am I changing (10filters x 4 times (every three months) or 40 filters a year??

On 2017-10-31 by Paul

I have a Bryant AC unit for my three year old home. When changing the filters, I noticed what looks like an inside filter. Does it need to be changed?

I have three places where I change filters. Two are on the ground floor and one is on the second floor.. The "inside filter" is with the one on the second floor. So I take out the regular filter and then it looks like there is another filter to the side.

On 2017-10-19 by Lindsey W Atkinson

I have a 3 ton air handler upflow Rheem system, trying to figure out how to properly installed Two brackets that came with this unit, I believe it is for the air filter, but some of holes don't line up? Could someone give me some pointers, for what I should do. Thanks.

On 2017-07-08 - by (mod) - can a new Carrier condenser be located 1-inch from the wall?

(mod) said:

No, Sylvia, that distance violates just about every manufacturer's installation instructions and guildelines - unless perhaps you have a piece of equipment rated for "zero clearance" - not something that I've seen. But this isn't an air filter question.

Details about clearances around HVAC compressor/condenser units are at CLEARANCE DISTANCE, HVAC inspectapedia.com/aircond/HVAC_Clearance_Distances.php

On 2017-07-08 by Sylvia Wahoske

Can a new Carrirer unit be located only 1 inch from the wall.? The other 3 sides have over 12 inches of space. Will the close location effect the efficiency of the new unit?

On 2017-06-16 by Key

Just bought a home it has a sanuvox uv unit on the return duct but can't find a filter anywhere. I see an old filter that is very dirty on the floor in the basement but no where to install a new filter

On 2017-06-06 by (mod) re: doors that block air inlet to the air filter or return air

M

When the door is open it blocks the return air - that is certainly going to increase the cost of operating the system and reduce its effectiveness too - the air flow will be restricted.

Can you put a door stop on the floor so as to keep the door a foot or more away from the return air opening? That'd help.

On 2017-06-06 by M

I have a a.c filter vent behind a door. Is this a good place or is it defeating the purpose? the room is an external room that leads outside and with the door open it covers the vent.

On 2017-05-20 by (mod) re: is it ok to find no air filter at the air handler if there are return air inlet filters?

Sure.

Glad to assist. I'd like to see photos of the situation. You can use the page top or bottom CONTACT link to send me photos and I can comment further.

On 2017-05-20 by Armando

I have 3 filters on the ceiling but was not able to find any on the air handler at the attic? Is this okay

On 2017-04-19 by (mod) cascaded air filters can be cleaned

Some HVAC system use use a cascade of air filters. Typically in first filter is one that can be removed and washed.

On 2017-04-19 by Tacoman

Hi, I just purchased a new home and when changing the largest of the three return filters I noticed there was a secondary filter inside the largest return. It is not two stacked on one another, there is a second slot to hold a filter that is perpendicular to the primary filter inside the return.

The primary filter is a 20*25*1 and the secondary filter is a smaller 10*10*1. The other two returns in the house are 14*20*1 and do not have a secondary filter inside the return. Unfortunately, I am at the office and do not have any specs for the hvac system other than it's a Trane, so I know that doesn't help much. Just curious how this setup works and why it is there.

Thanks!

On 2016-10-19 by lisa m. brady

I have a trane heating and air conditioner and I want to change out the air filter because something is wrong - we are only receiving "fan temp. air" verses cool- our thermostat says 83 and it stays on 75- I do not know what is wrong but now I can not even find where the air filter is!!!! Any thoughts?

On 2016-10-02 by (mod) The AC tech told me to not install a filter at the furnace if I have filters in the return vents

I think your technician is correct.

On 2016-10-02 by Macster

Hi..I live in central Florrda and I have 2 return vents.. One in the hallway 20x21x1 and another in the master bedroom 12x12x1... I also have a furnace with a slot that I could install a filter.. my question is, do I install a filter at the furnace or at the return vents? - The AC tech told me to not install a filter at the furnace if I have filters in the return vents because that will make the system work harder? - - is he right?... do you recommend a filter at the furnace versus the return vents?

On 2016-09-20 by Terry DuBois

I just in the last few months moved into a new mobile home. I have 3 filters inside my a/c return register, 2 of them are metal that resembles the filter in the hood of a stove & 1 regular type filter. The regular one I change everytime I pay my electric bill but the 2 metal ones I am not sure how to clean. What is the purpose of the metal ones. Have never lived in a place that has used these.

On 2016-08-26 by cvd6262

I'm worried about the air filter placement in a new system. My new AC/Furnace unit has worked great for the last year, but when I went to check the filter (located just before the blower), it's perfectly clean. I believe it isn't catching any dust because there is a 3-inch gap between the top of the filter and the side of the duct where it sits.

This allows dirty air to get sucked around the filter and into the blower. Is that correct? How tightly should the filter fit in its rack?

On 2016-07-21 by (mod)

From just your one line e-query, Anon, nobody can say where your system's air filter is located. But the article above suggests where to look. follow the ductwork; check the air handler, check the return registers.

On 2016-07-20 15:27:48.624409 by Anonymous

I can't locate the filter for our Payne central AC. I checked the intake vents, but no luck. Where is it?

On 2016-07-15 by (mod) re: can't even find the air handler or blower unit

Elaine you should be able to spot where cool air comes INTO your unit (supply registers) and where warm air is LEAVING your unit (the return register) - typically one or just a very few larger grilled openings. That latter is where to start looking for an air filter.

On 2016-07-15 by Elaine

I have a 1st floor condo unit. The condenser is outside but there is no air handler in my unit. There is no access to a crawl or attic space. I only have a thermostat and have no idea where a filter would be located. I have ductwork for AC. Heat is from baseboard/boiler in basement of building.

On 2016-06-13 by (mod)

Anonymous:

You can turn off the A/C fan at the thermostat or at the air handler unit until the A/C system has been repaired.

You should be sure that a clean air filter is in place - or at least whomever is maintaining the A/C system should do so.

You could block air flow or at least reduce it significantly by closing your supply register louvers.

Your landlord may be worried about indoor mold due to hot humid air, high indoor humidity, low air movement and may be running the fan as a stopgap measure. Discuss these concerns with your landlord.

 

The thermostat FAN ON switch may be in the ON position
or
The thermostat is calling for cooling and the air handler runs but your outside compressor/condenser won't.

See https://inspectapedia.com/aircond/Air_Conditioner_Diagnosis.php for some simple steps to follow.

On 2016-06-13 by Nancy

What is causing the air to blow if the air conditioner or the heat pump isnt cooling

On 2016-06-13 by Anonymous

Im renting and this house has a bryant a/c unit model BB5600240000e00 regardless thelandlorf has it pushing air into my flat even though the air isnt working
Im getting all kinds of dust in the house and have asthma and copd. Somethong is putting air in here and its making me sick.

On 2016-05-31 by sho

cant find the filter on a goodman package unit looked every where may not be one in how do I no where to put one in

On 2016-05-18 by Allen k

My Lennox central ac is installed on the roof , but the air filter needs to be changed in the attic ; I can't find the air filter in the attic which supposed to be under the ac unit .

On 2016-05-14 by (mod) are filters needed on both the return air inlets and at the air handler

No, Hilda. And doing so may restrict air flow more than is acceptable.

On 2016-05-14 by Hilda

I have a unit that is similar to that above in the first picture with the very dirty filter. Do I need to have filters on the return grilles as well?

On 2016-02-09 by (mod) re: where is the furnace or air conditioner air filter usually located

Typically the filters are at the return air inlet. If you found them there there may be no other filters at the air handler itself.

On 2016-02-08 by Stoddard Best

I have two carrier air conditioner units, horizontally placed in my attic. I am not sure where the filter is located within in the unit. I could take a picture and send you a copy if that would make it easier to locate the filters. I have replaced the filters at the ceiling register units. One unit is a 4 tons and the other is 5 tons.

On 2015-07-20 by Heat pump Air Conditioner/Heater system

I have a central heat pump with air conditioning and heating assist. On my Bryent system, they placed the filter in a very odd place. It is on the return side, but during the summer months, the refrigerationg coils drip condesation water all over the filter because it is right below it.

Half of the filter also gets sucked up into the plenum chamber where the A-frame coils are located, too. Consequently the air flow gets restricked, and the coils start to ice up causing even more water to drop down to the lower part of the intake plenum chamber.

Plus, when I go to remove the filter to change it, it is all worped out of shap, and usually damp, and hard to remove out of that little opening after removing the little access door. Whatever particals were on the filter will now drop down to the lower chamber as I try to remove the filter.

It seems to me that the filter should have been installed away from those coils, and on the other side of the return plenumn where it is dry, and a larger area for the filter. Why did they put the filter there?

On 2015-05-27 by Anonymous

Very helpful and detaild

Question: Should I remove the air filter installed at the air handler and just filter at the return air inlets?

My house has a central air unit and 2 return supply grills in each hallway. I always had a big filter in the main unit (16x20x4) and then one in each of the return grills (16x25x1).

Last year my unit was not cooling very well and the tech said I should not have filters in all 3 spots, and suggested I not put one in the main unit, just the hallways.

Now the house cools great, but the dust is over whelming. Is there some adjustment I should make by adding a central filter again, or just buying super efficient hallway filters? BTW, we have lots of pets.

Rox5704

Reply: Suggestions for filtering HVAC air at the return air inlet grilles

Rox:

In my OPINION what your HVAC tech said was reasonable.

I would NOT want to operate an HVAC system with no air filters - doing so leads to debris collection in the duct system (expensive to clean or correct later on) and debris clogging at the cooling coil of an air conditioner and debris clogging on the blower fan - reducing airflow further and creating system operating problems.

The problem with filtering ONLY at the air handler is that debris collects in the ductwork, especially the return ducts - that can be costly or even impossible to clean, depending on duct routing and the materials used.

So it's best practice to filter return air right at the return air inlet grilles just as your tech suggested.

You can try using higher efficiency filters at the return inlets (the inlet mounting grille may need to be changed to accommodate a thicker air filter) but choose your filters carefully. A thicker filter that is deeply pleated, by providing greater total surface area than a more flat air filter, can improve air filtration significantly without reducing the air flow rate through the device.

On 2015-02-16 10:39:26.023220 by peg

I live in a condo and have a carrier hvac- sometimes just the fan blows the warm air and cant hear the motor -lately the unit turns on every 15 minutes and runs for 10 then shuts off for 15 - is it because its so cold outside -shouls I be worries when I hear fan only- I change side filter every 2 monthe

On 2014-09-07 by (mod) -

Doug, yes if you don't change the filter you obstruct air flow, increase cooling or heating costs, and potentially cause coil icing (loss of cooling). If you eliminate the filter that's hard to reach you ultimately dust-clog the blower fan, cut its air movement ability, and increase system operating cost.

On 2014-09-05 by Doug

I have a air handler where there is no filter on the unit itself. There are 2 return ducts into the unit. In the ceiling where one return duct originates, I am able to easily reach and change the filter. The 2nd return duct origin is 18 feet high and has no accessible filter. Any suggestions? Do I have to get a ladder every month as well as change the cage so a filter can be placed, is having a filter on one return enough? Is it better to "add" a filter to the main air handler unit? Thanks.

On 2014-07-10 y Juan

I have a york unit, the model is a f2rp036h06g, not a window unit ) maybe a 1 ton to 1.5 tons. house was build in 2005. I have change the one in the ceiling, but is there a second one and were ?

On 2014-07-05 by (mod) -

Rosetta,

The air filter will have arrows on its edges indicating the direction of air flow through the filter. Install the filter so that air will flow in that direction through it.

Another clue besides air filter direction arrows:

On many filters one side has reinforcement on the air outlet side of the filter to prevent its collapse due to air pressure. It is important to respect the air filter's air flow direction requirements since installing an air filter "backwards" can allow the filter to collapse and become sucked into the HVAC system where in some designs the result can be a jammed blower fan, an overheated motor, and even a fire.

On 2014-07-03 by Rosetta

real simple:16X25X1 PLEATED AIR FILTER,WHICH SIDE GOES ON THE UNIT W/THE WEBBING?DOES THE SOFT SIDE GO IN FACING THE UNIT ITSELF ? RIGHT NOW THE SOFT SIDE IS THE DIRTIEST

On 2014-05-02 by Raquel

Great! Thank you!!!

On 2014-05-02 by (mod) -

Raquel you asked this question and we answered it at

https://inspectapedia.com/aircond/Air_Filters_HVAC.htm

On 2014-05-02 by Anonymous

I have questions regarding the filters for a commercial AC unit. We were told that our 2012 and 2013 units don't need filters inside our suite but rather the filter is inside the roof top unit. We also have a 2008 unit and for that we were told that we do need to change the filters inside our suite. We were also told that this is because of new regulations. So which filters should we be changing quarterly? We currently have filters at the roof top units and we also have filters in all the registers. Is this chocking our AC systems?

On 2014-03-23 by (mod) -

Shari,

I'd need to see some photos of your indoor and outdoor equipment to understand the question enough to give a helpful reply. I don't understand how a "Carrier unit" - presuming you mean an air conditioner or heat pump - could be providing heating or cooling to a building interior with "nothing inside".

On 2014-03-22 by Shari

My home is built on a slab. My Carrier unit is outside and I have nothing inside. Is the filter outside?

On 2013-02-27 by Rebecca

I am installing a new gas pack. One company suggested a unit with the filter at the air handler on the roof (as it is now). The other will install 2 filters at the returns. I have quite a bit of duct work on the roof, so the first suggested having the filter at the handler is more likely to filter out more as dust can get into the duct work along the path to the handler. Which is better?

On 2011-11-10 by rox

thanks so much. this makes sense. I will buy better quality filters for my hallways and leave the central unit alone.

On 2011-11-04 by (mod) -

Rox:

In my OPINION what your HVAC tech said was reasonable.

I would NOT want to operate an HVAC system with no air filters - doing so leads to debris collection in the duct system (expensive to clean or correct later on) and debris clogging at the cooling coil of an air conditioner and debris clogging on the blower fan - reducing airflow further and creating system operating problems.

The problem with filtering ONLY at the air handler is that debris collects in the ductwork, especially the return ducts - that can be costly or even impossible to clean, depending on duct routing and the materials used.

So it's best practice to filter return air right at the return air inlet grilles just as your tech suggested.

You can try using higher efficiency filters at the return inlets (the inlet mounting grille may need to be changed to accomodate a thicker air filter) but choose your filters carefully. A thicker filter that is deeply pleated, by providing greater total surface area than a more flat air filter, can improve air filtration significantly without reducing the air flow rate through the device.

On 2011-11-03 by rox5704

My house has a central air unit and 2 return supply grills in each hallway. I always had a big filter in the main unit (16x20x4) and then one in each of the return grills (16x25x1). Last year my unit was not cooling very well and the tech said I should not have filters in all 3 spots, and suggested I not put one in the main unit, just the hallways. Now the house cools great, but the dust is over whelming. Is there some adjustment I should make by adding a central filter again, or just buying super efficient hallway filters? BTW, we have lots of pets......

On 2011-08-26 0 by (mod) -

Ly,
yes you can install an air filter at the return register;
you might want to check the ductwork for cleanliness and if it's dusty dirty it'd be smart to clean the ductwork when you're changing the point of air filtration.

HVACR suppliers sell return air register grilles that replace a simple flat cover that you may already have. The new grille unit will include a recess intended to support an air filter.

And make sure ALL of the return registers get air filters if there is more than one.

On 2011-08-22 by ly2240

Hi, I have a furnace that's located in a hallway. I have to take the top cover of the heater off first before I can take off the cover of the blower underneath, in order to replace the filter. My question is can I move the filter from under the blower and place it at the return register? There are 4 airtight dry walls under the blower - will I need to add a return air plenum? Right now the filter is 14x24 inches and I am trying to make it bigger (20x30) if possible.

On 2011-08-01 by (mod) -

JZW

Sometimes we see a system installed with no air filter whatsoever. If you find that's the case in your system, you'll want a filter installed - at a location that is easy to access so that folks will actually change the filter on schedule. And check the blower fan assembly - if there was no air filter, or the filter was left very dirty for a long time, or was leaky, the blower may need cleaning.

You should not feel air coming OUT of the return register. If you do, something is blocked (or it's not the return register).

On 2011-08-01 by jzw

Great article. I've been trying to find the filter(s) for my ac unit. I cannot find it... Maybe it is inside. I will check. The unit is in the basement and fit to my 80+ years old house by the previous owner. It looked very much like the photo in the "Watch Out: If a building air conditioning or heating system air handler gets its return air right at the air handler" section. And it also has a register at the bottom. The return duct is there just like it is in the picture. But It stops about 15 ft from the unit and is closed at the end. I don't see it connecting to any of the rooms. So I wonder if my AC unit wasn't properly installed. Btw, somehow the register at the bottom blows out air instead of sucking in air. So I am not sure where the unit gets the air from.

On 2011-06-02 by (mod) -

Pam:

If you say your AC is "working" but is not cooling the house, I interpret that to mean that the system is "running" but not really "working" properly. Either there is inadequate air flow or the air flow is OK but it's not being cooled and dehumidified. Diagnostic suggestions are found in detail by clicking on the LOST COOLING CAPACITY article link found at the left of this page.

On 2011-06-02 by PAM

I WILL CHECK THESE PLACES WHEN I GET HOME. MY LANDLORD SAID THE BUILDER TOLD HIM THERE WAS NO FILTER IN THE HEATING AND COOLING UNIT. I FOUND THIS CANNOT BE RIGHT. MY AC IS WORKING BUT NOT COOLING MY HOUSE. THIS HOUSE IS ONLY 3 YEARS OLD! I WILL CHECK OVER EVERYTHING AND HOPEFULLY I WILL FIND THE PROBLEM MYSELF. BEEN WAITING ON THE REPAIR GUY FOR 3 DAYS!

...

Continue reading at AIR FILTER LOCATION - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see

Or see these

Air Filter Articles

• AIR FILTERS for HVAC SYSTEMS
  • AIR FILTER EFFICIENCY
  • AIR FILTERS, FIBERGLASS PARTICLES
  • AIR FILTER LOCATION
  • INSULATION BLOCKED COOLING COIL
• AIR FILTER MATERIAL RE-PURPOSED for FACE MASKS
• AIR FILTER OPTIMUM INDOOR
• AIR FLOW IMPROVEMENT, HVAC

Suggested citation for this web page

AIR FILTER LOCATION FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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