Results 1 to 8 of 8
  1. #1

    At the grill vs at the air handler filters

    I recently called our HVAC installer to ask about putting a 4" or 5" airfilter at the air handler (I think right term) after reading about the problems with the 1" filter we have now.

    He told me we could also get a 4" filter that he could install where our 1" filter is now (behind the grate in the walls or ceiling). I looked around but did not see any mention of that here. Are there any opinions about these?

    We have several different size intakes, anywhere from a 12x12 to a 16x25, so I assume they come in all different types of sizes.

    From what he said the installation is much less expensive, but since you have to buy more of them the cost adds up.

    Are there any opinions about these?

    Thanks...

    CT

  2. #2
    Join Date
    Aug 2003
    Posts
    907
    The closer to the air handler, the less leakage of air and dust there should be (is that an issue in your system?). Personally I would rather not have a bunch of different sizes to hunt down, but it depends on the price difference... It depends on your personal equation for cost vs inconvenience.

  3. #3
    Join Date
    Jun 2007
    Location
    south carolina
    Posts
    176
    The filters your talking about are pretty good however your on the right track with your thoughts on price. Also if the filters are in the grill then the duct work between the airhandler and the grill is subject to higher static preassure. Also if you leek air then it wont be filtered unless your filter is at the airhandler. The only reason i can think of for the grills is easy access so if this isnt an issue probably best to go in at the airhandler.

  4. #4
    Join Date
    Jul 2007
    Location
    Tulsa, OK
    Posts
    990
    Filtering at the return air grill is the best option. Yes high static can apply from it but who does'nt have it already? Unless a master pro more or less did your install and fine tuned and balanced your system and I extremely doubt it was. So that leaves a very simple reasoning left in regards to the dirt removed. Next time your somewhere and it is feasible to ask a friend, have them remove the filter at there grill and you most likelly will see the amount of dirt is almost none clinging to the plenum box and connected duct. Now look at yours if your is filtered at the furnace. About 2 lbs just where you can see before it disappears down the duct. Which do you prefer? In 30 years I've seen maybe 10 homes that had good static through out including all the ducts. I suggest you replace filters no matter the location every 30 days and make it a habit even if they look clean. If you have a new home and do this, your system never gets the neglect to get dirty.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,586
    If you have multiple returns. Then you might get longer life span out of some of the filters then others. Cost will be up, but so might air quality.

    Static is more of a concern then you might have been left to believe.
    The static with 4" filters could be enough that you can't cool or heat your house at OD design temps.

    Also, if your return duct has excess leakage,( they all leak ) the grille filters will increase the amount of air that the return duct pulls from unconditioned areas. Causing your heating and cooling bill to rise.

    So have your duct system checked first.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Aug 2003
    Posts
    907
    Quote Originally Posted by beenthere View Post
    (...)

    The static with 4" filters could be enough that you can't cool or heat your house at OD design temps.
    (...)
    What? You think 4" thick filters are worse than 1" thick ones? Wait, let me pick up my jaw, I dropped it somewhere around here...

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,586
    Depending on the MERV he picks yes.

    Also, many of the replacement media elements that HO's get at big box stores have high PD's, they aren't made as good as the OEM's.

    A merv 13 has a higher PD, then a merv 8.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    Aug 2003
    Posts
    907
    Quote Originally Posted by beenthere View Post
    Depending on the MERV he picks yes.

    Also, many of the replacement media elements that HO's get at big box stores have high PD's, they aren't made as good as the OEM's.

    A merv 13 has a higher PD, then a merv 8.

    It depends on the air speed (fpm) and filter construction (filter material, number and depth of pleats and the resulting effective filter area). Thickness usually increases filter area and therefore usually lowers the pressure drop. MERV is only loosely linked to pressure drop. Filters made with higher MERV material usually have more effective surface area to compensate. Even if a higher MERV with the same type of material and same construction means higher pressure drop, different materials can produce lower or higher pressure drops, all else being equal. Electrostatic filters can reach a higher MERV for the same pressure drop. Finally, the contractor can also increase the filter size to decrease air fpm, if a high MERV filter is desired.

    I wish that filters were rated for resistance to air flow in addition to MERV. Then people wouldn't have to resort to oversimplifications, and it would be more obvious which filters offer the best MERV for the lowest pressure drop "price". Until that happens don't expect HOs to choose well-made filters, but don't blame them: the HVAC industry isn't giving them the necessary information to make a correct choice. The only tool they've been given is the MERV rating. The "lemon law of commerce" states that if there are two products that appear the same to a consumer, in the absence of any other information the consumer will choose the cheapest one. Even if the cheapest one is of much lower quality. So, HOs buy the highest MERV rating without regards for the pressure drop, because they aren't being told otherwise on the packaging. The HVAC industry is responsible for the bad filter choices made by HOs.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event