Replace A/C return in floor to accept filter (grill, installed, master bedroom)
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Hello,
I want to relocate the filter housing for my central A/C from near the air handler to the return(s). The current filter housing is in the ductwork in my crawlspace, which is not exactly ideal for convenience of changing the filter, nor avoidance of things with 8 legs. The crawlspace is open to the basement, so it's sort of half crawlspace and half basement. I'd like to just remove that filter and replace my return register grille, which is in the master bedroom on the second floor, with one that will accept a filter. There is also another return in the floor of another bedroom. Originally I'd thought it was intended to try to blow some air up into that room, since the A/C was only installed on the first floor, but I recently realized that it is actually a return, which explains why it never seemed to do anything. Personally this seems like a very poor idea, since it would be even more prone to allowing dust, dirt, hair, etc to get into the system due to being installed on a horizontal surface. I would assume that I would also need to add a filter to this return as well, correct? I just don't know if having two filters at the returns rather than one at the air handler might stress the system too much. Perhaps using a more "high-flow" type filter would help? I'll also have to try to find a return grille that will take a filter to replace the one in the floor, which I was having a little trouble finding in my preliminary research, but I still feel some sort of filter would be a good idea for that one anyways. Any input is appreciated. Thanks!
Depending on the air handler, they make a universal filter box that goes under the air handler. Just requires the unit be taken loose and raised up about 3". In most applications, the unit does not have to be completely removed or disconnected from the refrigerant lines. I'd chat with a local A/C tech about it and get an idea from him about cost. The box only here is about 60 bucks.
Location: East of Seattle since 1992, 615' Elevation, Zone 8b - originally from SF Bay Area
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We have two filters on the unit in the garage, but the return upstairs has a hinged louvered door so I just had my local HVAC shop cut me a hunk of the washable filter material to fit inside. I wash it twice a year, and still check the filters in the garage, but have not changed them in 15 years because they still look like new.
The required surface area for a non-pleated filter works out to about 1sq/ft per ton of A/C so measure the return grills to determine if your grill sizes are adequate for filtering.
The returns have accumulated dust and dirt over the years, especially the one located on the floor. The returns should be cleaned. Tip...don't buy the super duper filter that the duct cleaning company will try to sell you. Cheap filters are much better for the system and anything that would actually improve air quality would need to be a 4" deep filter to avoid the side effects of air flow resistance.
The return duct will have to be free of air leaks. Any dust that gets sucked thru duct leaks will no longer be filtered prior to reaching the equipment. The blower wheel and cooling coils love to collect dust.
New filter locations will need to have the filter fit well to avoid having the dust bypass the filter.
We have two filters on the unit in the garage, but the return upstairs has a hinged louvered door so I just had my local HVAC shop cut me a hunk of the washable filter material to fit inside. I wash it twice a year, and still check the filters in the garage, but have not changed them in 15 years because they still look like new.
You might want to research filter type as if not large enough return many restrict flow and lessen efficiency. Newer unit come with built in filter and of the type for best flow and cooling.
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