Furnace filtration...single main vs separate?

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Old 10-13-20, 10:36 AM
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Furnace filtration...single main vs separate?

Is there a major difference between having a filter on each return grille vs just a main return on the return next to the furnace?

right now I have 3- ceiling return filters and i was just thinking it would be a lot easier to have just the one filter but not sure if 3 separate filters might last a lot longer vs one or some other differences?
 
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Old 10-13-20, 10:43 AM
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If all the filters are the same size having one in the trunk line will cause more flow resistance than the three in the ceiling. But, I don't think it's enough to worry about. I'd go with what is easier for you to maintain but I doubt you need to change the ceiling ones very often.

I have three in my house. Two are in the wall about a foot off the floor and they need regular replacing. The one near the ceiling only needs replacing every couple years.
 
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Old 10-13-20, 11:20 AM
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I see little reason to have filters for the return vents other than the main filter at the furnace plenum. As has been mentioned many times in this form, the return air filter at the base of the furnace is there to protect the furnace / A-C unit from debris. Adding filters at room return vents seems useless. It certainly does not filter the air you breath. So it's filtering the air going to the main filter! ??? Just changing the main plenum filter should be all that is necessary.
 
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Old 10-13-20, 01:28 PM
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When the filter's remote from the air mover, any inleakage to the return duct is unfiltered air with various contaminants, some of which can be deposited on the blower, blower housing. heat exchanger(s) and coil; and some of which can be recirculated to the home.

As I've said often, it's quite likely your air mover is delivering substandard flow because of improper duct design and/or installation, greatly increasing the risk of blower motor and compressor failure. The absolute last thing you need is two sets of filters (and two resistances to flow). Do not under any circumstance add filters if there's already a filter. And if you're upgrading the MERV, do modify the duct system to compensate for the increased resistance of the more efficient filter.
 
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Old 10-13-20, 01:35 PM
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And always check downstream of the filter to make sure there's no construction debris to be recirculated to your living area forever. These images were taken in a DE home billed as a "Health House". The duct is a return duct between the wall-mounted filter and the air mover that separated due to improper installation. Note the debris inside, to include a plastic beverage container.



 
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Old 10-14-20, 05:30 PM
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Thanks for the replies. I wouldnít keep both. I want to get rid of the grille ones and just use a main one. Just a bit of a pita having to get a ladder every couple months to change the filters.

also bring up a good point that any leakage isnít filtered. Although I just installed the ducting 2 years ago with as much mastic as you could use but Iím sure thereís a possibility of a leaks.

anyone know of a filter slot that I can cut into the return plenum so I donít have to take anything apart?
 
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Old 10-17-20, 10:49 PM
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Please post images of the furnace showing plenum from front and side. It'd also be good to have make and M/N of furnace and outdoor unit.
 
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Old 10-21-20, 05:25 PM
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Your best bet is a MAC (media air cleaner) similar to Honeywell F100 MERV11. With the M/N's and images requested on the 18th, we can tell you what size MAC and whether any duct mods are necessary to install it.
 
 

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