I could use advise to change my air handler filter

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Old 04-13-18, 10:07 AM
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Question I could use advise to change my air handler filter

Hi all.
Specs: Armstrong Air, SA11694.
Our furnace technician simply said the filter is 15" x 20" x1", and change it every 2-3 months.

I did a search using "Armstrong Air, SA11694", but I didn't go very far.
What brands should I look for?
Any web site in particular?

Thanks in advance guys

DPC
 
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Old 04-13-18, 10:10 AM
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Any store will have a variety of filters. All that matters is the size. 15x20x1.
 
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Old 04-13-18, 10:12 AM
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Great!
Thank you XSleeper
 
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Old 04-13-18, 11:52 AM
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Just don't buy the super duper ones that will filter out atoms. They can restrict your system. One step above the cheap blue will do fine and keep your system clean...which is what they are supposed to do, not filter the air that you breathe. $5-8 for a pack of 3 max.
 
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Old 04-13-18, 01:31 PM
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You should take note of which side is which. Air flow direction is noted on some filters.
 
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Old 04-17-18, 10:43 AM
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Right Sizing Filter Racks

Not only are Return-Air ducts grossly undersized but also filter rack areas are also grossly undersized…

This is Extremely Important when Sizing filter rack areas…! Time to start checking filter airflow fpm velocities...!

NCI is the National Comfort Institute, Inc.; they say to verify the pressure drop for that filter at the design CFM & velocity and compare it to the available static pressure of the system, the pressure drop through residential systems should not exceed 20% of the fans rated static pressure. A .5" Rated system x .20% is .1" of pressure-drop...

However; then they show the various WRONG steps in Sizing filters for the CFM airflow & fpm velocity required; the problem is that they use the listed total square footage of the filter and ‘never figure the actual open area or AK ‘of the filter, which makes a huge difference in selecting filter sizes for a particular required CFM & fpm velocity.

After much figuring I have found that the ‘open-air or AK’ of the low pressure drop filters is at around 0.645%. .Return-air filters are not 100% open-air; for example RA grilles at 400-fpm velocity have a usual pressure-drop of .03” while cheap filters have around a .08 or.1” pressure-drop at 300-fpm velocity indicating many times more airflow resistance…!

A typical 16x25 or 20x20 is a total 400-sq.ins. x* .645% is 258-sq.ins open-air Ak / 144 is (525-CFM / 1.791666-Ak is 293-fpm velocity); that’s only 350-CFM per ton on a 1.5-Ton A/C…!

That’s how we have to size filters to come close to the manual D requirement of 300-fpm velocity… Some say use 250-fpm, I kind of like 280-fpm as being okay.
 
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