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Straphanger
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join:2001-12-08
Whitestone, NY

Straphanger

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Air Return Filters

I moved into my new house but noticed something a little weird with my central air return. In my air return register, there's a 20x30x1 pleated filter. Following the air return duct work into my attic, I found that there's another 20x20x1 filter where it enters the air handler. Is it necessary for me to have both filters in place and would this have any effect on the efficiency of the system?

John97
Over The Hills And Far Away
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join:2000-11-14
Spring Hill, FL

John97

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My house has filters on all of the returns and the "filter holder" at each air handler is empty.

Tex
Dave's not here
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join:2012-10-20

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Having an additional filter at the air handler could adversely affect external static pressure (airflow), performance, efficiency and the compressor. Some air handlers have a built-in filter rack and they come from the factory with a filter installed. Perhaps the installers forgot to remove it. I recommend removing it.
iknow_t
join:2012-05-03

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said by Straphanger:

I moved into my new house but noticed something a little weird with my central air return. In my air return register, there's a 20x30x1 pleated filter. Following the air return duct work into my attic, I found that there's another 20x20x1 filter where it enters the air handler. Is it necessary for me to have both filters in place and would this have any effect on the efficiency of the system?

it works like this. the more filters inline, the more the airflow may be reduced depending on the system. BUT, depending on the leakage of the ducting, and the efficiency of the filters, the more filters are used, the cleaner the ducts, and outgoing air is, so it's a tradeoff.. usually, one source of filtration is used.. the filter in the air return register is the most important, as it will keep the dust down in the ducts.. btw, you don't want a leak where a filter used to be, but isn't, so, that would have to be sealed off so there's no leaks if you go that route..

Sly
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join:2004-02-20
Tennessee

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I only use filters on the air returns. The filter on the air handler, I removed. I clean the inside coil once per year to remove any stray cat hair that got through. IMO, you don't want to have filters on both the returns and the handler. It will restrict your air flow and reduce your efficiency.

pende_tim
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join:2004-01-04
Selbyville, DE

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You could leave the pleated one in the return register and change out the one at the furnace to a "30 day" cheapie. The 30 day filters have very low restriction so should not affect air flow in any meaningful way when in series with a pleated filter. 2 pleated filters in series can hurt performance.

The pleated one will capture 99.99% of the "stuff" in the air return. The 30 day filter will get anything that may leak into the ducts. Since this is after the pleated filter there should be very clean air at the furnace. With clean air, the 30 day filter should last a year or more.

After a few months inspect the 30 day filter and see if it is picking up any significant dust. If it is, there may be leaks in the return ducting that need to be addressed. If it is staying clean, it can be removed or left in place, your option.

Msradell
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join:2008-12-25
Louisville, KY

1 recommendation

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As everyone mentioned having the 2 filters in series COULD adversely affect the system operation. Another possibility is that the HVAC contractor DESIGNED the system to operate with the filters in series to keep the system cleaner. Since this is a new house I would contact the company that installed the HVAC system and discuss the issue with them prior to making any changes!

Straphanger
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Whitestone, NY

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said by Msradell:

As everyone mentioned having the 2 filters in series COULD adversely affect the system operation. Another possibility is that the HVAC contractor DESIGNED the system to operate with the filters in series to keep the system cleaner. Since this is a new house I would contact the company that installed the HVAC system and discuss the issue with them prior to making any changes!

Wish I could do it but new is relative to me. The house is one I just bought but it's 80 years old refitted with an attic-based central air that looks to be 5-10 years old.

So the consensus seems to be that it'll likely reduce efficiency but isn't necessarily a terrible thing. I can try removing the 20x20x1 filter from the air handler and see if that helps the air handler push more cold air into the living space. Guess it can't hurt if I have the 20x30x1 at the return register.

Msradell
Premium Member
join:2008-12-25
Louisville, KY

Msradell

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If I was going to eliminate one it would probably be the one at the return. If you have one at the air handler itself it will ensure that nothing gets to the coils. You just have one and the return anything that infiltrates into the ductwork or come from the ductwork will end up in the coil.