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  1. #1
    Join Date
    May 2008
    Posts
    21

    Tight squeeze on AC filter

    I have a 12x36x1 return grill. I have a 3 ton pkg unit. I just noticed that my Boair filter is sized 11 1/4 x 35 1/4 x1. I had about a 1/4 inch space around filter that was pulling air into return duct. I put a 1/4 inch high density foam weatherstrip around my filter to make a better seal. Good idea?

  2. #2
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,541
    As long as the foam doesn't get pulled into the unit. Maybe try to find a little better fitting filter next time around. Some are sloppy and some fit much better.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    The filter is almost certainly too small and the type/brand too restrictive.


    Check the air flow in the farthest room with and without the filter to see how much air flow is being lost.

    Yes making a tight seal to prevent bypass air is a good idea ,just not with a restrictive filter.

  4. #4
    Join Date
    May 2008
    Posts
    21
    So Dash
    Would it be better to allow some air to bypass if I use that filter?
    I am waiting on an Accumulair Merv 6 pleated. Would that be a better choice for airflow?
    Are you familiar with Air-Care electrostatic? www.air-care.com
    Is $7-$10 per filter per month a reasonable expense? (I haven't bought a filter in last 10 years)
    Should they really be changed every month?

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    First your filter is on the small side for the system size.without out seeing/knowing the rest of the duct system ,can't tell from here.

    You need a Pro to test the static of the duct system,filter included,to tell you what is the best course.

    Restrictive filters and duct systems reduce the systems capacity,which can cost a lot more then the filter changes cost.

    As a minimum we'd like to see a MERV 8 filter,4" thck pleated ,usually changed 9 to 12 months apart.

  6. #6
    Join Date
    May 2008
    Posts
    17
    Your return grill should have a lip inside it for the filter to rest against. all filters are a 1/4 inch shorter then the size stated on them.

  7. #7
    Join Date
    May 2008
    Posts
    21
    Quote Originally Posted by sondown View Post
    Your return grill should have a lip inside it for the filter to rest against. all filters are a 1/4 inch shorter then the size stated on them.
    Yes it does. It is in ceiling. Can't change size of return grill. House was built in 1967 with a 2.5 ton AC. Now has 3 ton. This is So.Fla. I noticed some "dust" has been bypassing filter and accumulating on black fuzzy insulating material that lines return grill box in ceiling. Is this normal to have some air seeping around sides of filter? Will this "dust" cause any problems either to AC unit or return box ?

  8. #8
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Ideally no air will bypass the filter,what does will end up on the cooling ciol,which is a merv 6 filter.


    If the ceiling box is deep enough ,it can be modified to accept a 4" thick pleated filter,for less resistance then a 1" pleated.

    Adding a second return may be an option to increase filter area.

  9. #9
    Join Date
    May 2008
    Posts
    17
    Do you change the filter often or do you wait until the filter is fully coated in dust. This may be the reason dust is getting by the filter.

  10. #10
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,933
    Mtyogi17, dash has given you all very worthwhile and accurate advice. I work in a colder region where not only have restrictive filters created problems with cooling systems freezing up, but they have also wiped out many furnace heat exchangers.

    A filter needs to foremost be able to eliminate contaminates in the air that are large enough to do damage to the HVAC system. Secondly, a filter needs to not be restrictive to air flow to the point that it will create any operational issues with the HVAC system. Lastly, if the filter sizing can be large enough to not further restrict the air flow, a filter may be able to be used to increase the quality of the air for occupants of the dwelling.

    HVAC air filters are foremost for the protection of the HVAC equipment, not for improving air quality for human health. There are many whole house filtration systems available that can be installed for air filtration to improve the air for health purposes. These filtration systems are not inexpensive, but then, neither is replacing HVAC sytems due to restrictive filters.

    As to your original concern; you did good by using the sealing tape. Absolutely no air, not even from an opening from a removed screw, should enter the air going to the HVAC equipment.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  11. #11
    Join Date
    Dec 2007
    Posts
    89
    get the correct size

  12. #12
    Join Date
    May 2008
    Posts
    21
    Quote Originally Posted by RoBoTeq View Post
    Mtyogi17, dash has given you all very worthwhile and accurate advice. I work in a colder region where not only have restrictive filters created problems with cooling systems freezing up, but they have also wiped out many furnace heat exchangers.

    A filter needs to foremost be able to eliminate contaminates in the air that are large enough to do damage to the HVAC system. Secondly, a filter needs to not be restrictive to air flow to the point that it will create any operational issues with the HVAC system. Lastly, if the filter sizing can be large enough to not further restrict the air flow, a filter may be able to be used to increase the quality of the air for occupants of the dwelling.

    HVAC air filters are foremost for the protection of the HVAC equipment, not for improving air quality for human health. There are many whole house filtration systems available that can be installed for air filtration to improve the air for health purposes. These filtration systems are not inexpensive, but then, neither is replacing HVAC sytems due to restrictive filters.

    As to your original concern; you did good by using the sealing tape. Absolutely no air, not even from an opening from a removed screw, should enter the air going to the HVAC equipment.
    Good Advice
    I believe it was "beenthere" who advised to compare airflow and cooling temp between Boair electro filter and Accumulair Merv 6. I will do this. If Acc Merv 6 is better I will use it and just pay for replacements.
    All older homes in So Fla with pkg units have undersized returns as most homeowners have replaced with slightly larger units to deal with this weather. Increasing size of my return or filter is not feasible to me. My last AC survived 15 years.
    Thanks All

  13. #13
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Beenthere is good,no great, but can't find that on this thread,did find "Check the air flow in the farthest room with and without the filter to see how much air flow is being lost.",which acomplishes the same thing.


    We are in Florida and there's usualy a way to increase the return,maybe you need a different contractor.Not always easy ,but usually a way,and yours needs it.

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