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  1. #27
    Join Date
    Jul 2004
    Posts
    322
    I just spent 8 days testing 6 different pleated filters. I tested them on 2 different airflow settings. 3 electrostatic, 3 weren't. MERV ranged from 6 to 11. I also tested them new and after spending 24 and 48 hours with the fan running constantly. I didn't directly test pressure drop but instead tested the amps on my ECM blower which is designed to keep constant airflow. What I found:
    (1) Higher MERV didn't necessarily mean greater pressure drop.
    (2) Electrostatic didn't necessarily mean greater pressure drop
    (3) Electrostatic invariably loaded up quicker

    So the moral seems to be change your elecrostatic frequently if you use them. Also, most allergins are fairly large particles, compared to smoke for example, so a higher MERV may not give you greater allergy relief and they cost a lot more. Also, if you are allergic to dust mites, humidity control may be more important.

  2. #28
    Join Date
    Aug 2003
    Location
    Central Kentucky
    Posts
    6,247
    Originally posted by fat bob
    I didn't directly test pressure drop but instead tested the amps on my ECM blower which is designed to keep constant airflow. What I found:
    (1) Higher MERV didn't necessarily mean greater pressure drop.
    Try checking the pressure drop,you will be surprised.

  3. #29
    Join Date
    Jan 2002
    Location
    Ft.Worth,Tx
    Posts
    4,584
    Well the truth about an electrostaitc filter is you would need to have the fan run continously in order for the static to build up and work correctly.
    How do I know this, I went to Dust Free in Rowlett,Texas to the factory were they are made.This is the same filter Paul Harvey sells on the radio show.

    .55% restriction out of the box.This is on the label.

    I used to sell them in the early 90' but, had so many problems with frozen coils, crack heat exchangers, I don't recommend them anymore.

    If you want good indoor air quality then go to 4"pleated mounted in the return next to unit.

    Change the filter every 6~8 months and your allergy problems will go away. And if you go to allergy doctor he can prescribe the filter and insurance will pay for it.
    "Everyday above ground, is a good day".
    "But everyday that you have made a difference in someones life, may insure you stay above ground a little longer".<aircooled>

  4. #30
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Don't let anyone sell you (or buy one on your own) a "better" filter,without testing the ESP(External Static Pressure)first.


    Paul Harvey,has killed more compressors and heat exchangers than anyone else ,in the world!!

  5. #31
    Join Date
    Feb 2005
    Location
    Dothan, Al
    Posts
    3,453
    My sentiments exactly, david
    Definitely slows air flow down.

  6. #32
    Join Date
    Feb 2005
    Location
    Richmond
    Posts
    480
    Electrostatic filters are pretty efficent. Put one in on my gas furnace; was white when I bought it and after only 2 weeks it was completly BLACK! And it says on the package "The normal change invertal is 3 months" I don't think I would feel any air coming from my vents after 3 months!

  7. #33
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304

    Measuring vs. rules of thumb

    I am impressed that at least *one* pro recommends actually measuring ESP before making a judgement. Not all systems are the same, some are choked for return capacity and some are generous. It has been my experience that if you have generous return capacity (and generous filter area) then one has little to fear from a higher restriction filter. I have measured it and it doesn't seem that difficult.

    This could well be a business opportunity for HVAC pros. I imagine measuring ESP (or simply return vacuum) and then offering to enlarge return capacity and filter area to solve the problem. Get into a dialog with the homeowner as to what either of you can do that will prolong the life of the system.

    Regards -- P.Student

  8. #34
    Join Date
    Apr 2004
    Posts
    7,680
    That goes without saying. Its been repeated a bazzion times here before but a good point non-the-less.

    Electroninc and Electrostatic Air Cleaners are two different beasts all together.

    Aircooled made a valid point also in that airflow is what makes them work. However in a typicle residential system the velocity avaialble and the velocity needed to actualy produce the electostatic charge are very different and frankly unattainable without exceeding the ESP. They mostly just grab dirt becuase they have internal filters like Robo said which are not much better than cardboard. I've always wondered myself why some people want their HVAC system to clean their homes for them.

    Aircooled, I think you can get them prescribed but getting the insuracne to pay for them may be pushing it, however, if you are one of the few that have enough medical expenses it can be added into your tax deduction but for the most part that doesnt get you there either.


  9. #35
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Why wouldn't a home owner want his A/C system to "clean" the air?

    Now I totally understand that not all duct systems are designed for the pressure drop of better filters,but many can be reworked.

    Why buy a HEPA Bypass type filter,when you can have a media filter clean the air and keep your coil "cleaner " than a standard filtr?

    Not saying that the media is equal to the HEPA,just a that the media should do a good enough job for most peoples needs.

  10. #36
    Join Date
    Feb 2005
    Posts
    9
    Have one more question regarding this subject which interests me. I plan on upgrading my existing system to a Hydro Air system with two air handlers. Do media filters like an April Air on the return air side reduce air flow like the pleated or electrostaic filters you are refering to?

  11. #37
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by traron
    Have one more question regarding this subject which interests me. I plan on upgrading my existing system to a Hydro Air system with two air handlers. Do media filters like an April Air on the return air side reduce air flow like the pleated or electrostaic filters you are refering to?
    Yes ,about the same as media,all depends on the size of the filter.

    Adding Hydro coils is similar as well.The duct system can and should be designed or redesigned to handle the "extra" pressure losses.

  12. #38
    Join Date
    Sep 2004
    Posts
    119

    Talking dirty

    Ever cut open an electrostatic filter.I did on an old one
    lots of dirt.Read an epa article if not properly maintained
    can grow air born bacteria.Also confuse variable speed
    blowers.Engineering point that most centrfugal blowers
    are great at discharge return air is there weak point.Think oversized return.Like
    a well pump may have 50 ft in head but look at suction
    be good to be 10 ft.

  13. #39
    Join Date
    Jul 2003
    Location
    Philadelphia Pa.
    Posts
    461
    duct dr:

    Yeah I noticed that my OM suggests cleaning every 3 or 4 months depending on conditions. Here are my conditions:

    I have a VS blower that is set to run continuously in the winter when the house is occupied. This helps distribute the air between multiple floors and clean the air as it moves through the system. I also have a smoker in the house which tends to increase the gunk build-up.

    When I used standard and electrostatic filters I got into the habit of changing them every month regardless of the instructions so now I continue to clean my cells every month since it is no big deal and easy to do.

    During the periods of Late April and May and late September to mid October when the system doesn't run much, I don't bother to clean.

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