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  1. #1
    Join Date
    Jul 2009
    Posts
    38

    Filter pressure drop question

    I have a Carrier Infinity system and was using Honeywell MERV 12 filters without much of an issue, lasting about 6 months. I switched to Filtrete 1550 (16x25x4) and got a "dirty filter" notice on the controller after about 2 weeks. Seemed odd so reset the filter and the notice came back two weeks later. I replaced the filter (only because pulling it out destroyed the filter as it didn't have any tabs to help pull it out of the slot) and it looked somewhat dirty, but I know you can't tell just by looking.

    After replacing, I looked at the static pressure:
    Low speed - 525 cfm - 504 rpm - Static press 0.16

    Med speed - 792 cfm - 681 rpm - static press 0.28

    High speed - 1194 cfm - 1022 rpm - static press 0.63

    We run the fan on low continuously, but did before with the Honeywell filters. The pressure seems really high. My HVAC guy gave the generic "just replace the filter" response but was not knowledgeable about the actual pressures and didn't even realize that the Infinity system uses pressure to detect when to replace the filter, rather than time.

    Should I switch filters again (maybe I can ebay the Filtrete filters)?

    Thanks

  2. #2
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,826
    Do you need that level of filtration? I'm very pro IAQ but not at the expense of killing the HVAC system unless it's life and death for the consumer. And if that were the case, I'd recommend a HEPA filtration system that doesn't filter 100% of the air going through the air handler 100% of the time. I'd also recommend tightening up the home so that the natural air exchange is reduced and mechanical air exchange can control the amount of exfiltration/infiltration for a healthier environment. The prime benefactors of the high MERV filters are the manufacturers of those filters. The average citizen needs nothing more than about at MERV 8 for great protection. Well, unless you've got a science lab in your house that's spewing chemicals into the air on a regular basis.

    If youre health dictates a higher MERV value, then why not purchase something that is professionally installed and maintained so you don't have to worry about obtaining media? Or an electronic air cleaner properly installed AND professionally maintained. (The second part of that is usually the hardest part of an EAC purchase.)
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,946

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,392
    The 3M material starts out OK but with the least amount of dust on them, get really restrictive.

    I use the Honeywell "Popup" medias which are MERV11. Also the F200 medias are MERV11 and is a charged media type where static helps grab very fine particles. 2 good alternatives to the FC100 for not much more money. I get a year out of the popups.

  5. #5
    Join Date
    Jul 2009
    Posts
    38
    @skippedover - I do not "need" that level of filtration. It is only a matter of "as long as, might as well" - as long as I'm getting new filters, might as well get the best ones to clean the air in the house - we are running the fan continuously partially to balance temperature, and partially to filter the air.

    @BaldLoonie - I hadn't seen those popup filters. They are awesome as long as they hold their shape. I'm always looking for ways to save space.

    Do y'all think that these filtrete filters are "killing" my system as skippedover says with those static pressures? We don't have any pets, our ducts are fairly clean, and we have a wood stove (sealed firebox) that we use in the wintertime. I did find a note I had from the summertime that the pressure with the Honeywell MERV12 filter dirty the pressure read: High stage - Airflow cfm 1008 - Blower rpm 845 - Static press 0.41

    Thanks,

    Steven

  6. #6
    Join Date
    Jan 2006
    Location
    Powell River, BC, Canada
    Posts
    762
    Skippedover is right. Those 3M filters have the airflow qualities of a sheet of cardboard. I have found more cracked heat exchangers in units using them than any other type. 1" filters are for keeping dirt out of the equipment, they're not meant to be an IAQ solution. If you desire greater filtration, look at getting a 4-5" pleated filter or a combination media/EAC system.
    Where are you? Are you done yet? I got ONE more call for you.....

  7. #7
    Join Date
    Jul 2009
    Posts
    38
    Quote Originally Posted by gasguy View Post
    Skippedover is right. Those 3M filters have the airflow qualities of a sheet of cardboard. I have found more cracked heat exchangers in units using them than any other type. 1" filters are for keeping dirt out of the equipment, they're not meant to be an IAQ solution. If you desire greater filtration, look at getting a 4-5" pleated filter or a combination media/EAC system.
    @gasguy - they are 16x25x4 filters.

  8. #8
    Join Date
    Jul 2002
    Location
    Zelienople, Pa
    Posts
    2,965
    Those 1" are very restrictive out of the box new. There is a lot less surface area and they load up very fast.
    Go back to your 6 month interval with the honeywell filters.
    Why did you switch?
    How tall are you Private???!!!!

  9. #9
    Join Date
    Jul 2009
    Posts
    38
    @Gunnery Sergeant Hartman - got a good deal on a box of 4 filters. Didn't seem substantially different than the Honeywell and the MERV ratings seemed similar based on what I could find that attempted to compare.

    And these are 4" filters, not 1" filters.

  10. #10
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,826
    Sorry Sarge, some peeps are confusing your 4-inch filters with the standard 1-inch Filtrette. I do understand your reasoning in selecting the higher MERV but you need to understand that the smaller the particles removed, the smaller the spaces between the filter elements and the faster they clog up. I was a to a home recently that has 4 small dogs. I tested the static with the old MERV 11 filter in place (.8 IWC) and with a new one (.44 IWC). The owner claimed the "old" one was only 1-month old. Based on that I recommended monthly replacement. That can add up if they're expensive filters but yes, the equipment suffers is there's insufficient airflow in both heating and cooling seasons. Hence my question of whether you really need that level of protection for known health issues. If yes, then you have to pay the price to keep things as clean as possible and at the same time protect the equipment. If you can, however, survive nicely with a lower MERV value, such as 8, then I'd highly recommend you consider that option. FYI, MERV 8 is taking more out of the air than what you'll find on a nice, country, fresh air spring morning in the great outdoors. Above MERV 8 you start to approach laboratory conditions. So, if that's you need, so be it. But then again...if not...
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  11. #11
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,159

    These readings are about the same resistance

    Quote Originally Posted by sastexan View Post
    I have a Carrier Infinity system and was using Honeywell MERV 12 filters without much of an issue, lasting about 6 months. I switched to Filtrete 1550 (16x25x4) and got a "dirty filter" notice on the controller after about 2 weeks. Seemed odd so reset the filter and the notice came back two weeks later. I replaced the filter (only because pulling it out destroyed the filter as it didn't have any tabs to help pull it out of the slot) and it looked somewhat dirty, but I know you can't tell just by looking.

    After replacing, I looked at the static pressure:
    Low speed - 525 cfm - 504 rpm - Static press 0.16

    Med speed - 792 cfm - 681 rpm - static press 0.28

    High speed - 1194 cfm - 1022 rpm - static press 0.63

    We run the fan on low continuously, but did before with the Honeywell filters. The pressure seems really high. My HVAC guy gave the generic "just replace the filter" response but was not knowledgeable about the actual pressures and didn't even realize that the Infinity system uses pressure to detect when to replace the filter, rather than time.

    Should I switch filters again (maybe I can ebay the Filtrete filters)?

    Thanks
    AS YOU WHOLE DUCT SYSTEM. Think about how much fan HP it takes to move the air through this kind of resistance. Take the guys advice about the MERV 8 and then look at your electric bill
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  12. #12
    Join Date
    Jul 2009
    Posts
    38
    Our electric bill is pretty low relatively for our house size. When we replaced the HVAC system 2 1/2 years ago with the Infinity, our installer did add a return as he calculated we didn't have enough air coming in. The system is very quiet still (doesn't seem to be louder with the Filtrete versus the Honeywell), even on high speed, whereas the old one you could hear it sucking air - sounded like it was strangled.

    I definitely won't get any more Filtrete and will switch back to the Honeywell - only question is, do I just get rid of the 3 filters I still have or just use them up and don't worry about it?

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,765
    Sell em to a neighbor. One that isn't your favorite.
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