Two large pipes or ducts extend from the package unit.
Attic ac unit filter location.
You say you changed the two in the living areas suggesting that you have a dual zone system 2 floors.
Changing the filters in the hvac unit in this case your air filter is most likely located right next to your furnace or air conditioning system air handler.
Look for a filter slot right where the return plenum contacts the blower fan assembly marked as air filter slot and yellow arrow in my photo.
Well mainly it s a way to save space.
Attic hvac systems save space.
The filter is probably at the air intake not in the furnace blower unit up in the attic.
It s generally located in your attic basement closet or crawlspace.
Typically the unit would be found in a basement an attic or sometimes in the back of a closet.
The air handler is the large metal box containing the fan and fan motor.
Most updated central air conditioned homes have a new air conditioner split system meaning the ac is broken up into parts.
The air filter is usually located in the return air duct or blower compartment before the return air reaches the air handler.
The return air plenum on an attic or basement air conditioner blower unit will usually be a large metal enclosure about the same dimensions in width and height as the air conditioner blower unit itself.
One is the conditioned supply air that serves the house with warm or cool air attaching to the vents in every room.
The 2nd duct is the return duct that attaches to the return air vents and draws the stale air out of the house through the filter and conditions it again to return.
This air handler has a filter base under the unit.
There might be two removable front panels and you may have to lift the top one off first.
So why put an hvac system up in the attic at all.
The air filter might be on top below or on the side of the air handler depending on what kind of air handler you have.
An outdoor unit which houses the fan condenser and compressor and an indoor unit which holds the evaporator and fan.
If you don t see a panel on or near the air handler indoor unit that has filter stamped on it then try checking these locations.