Page 1 of 2 12 LastLast
Results 1 to 13 of 26
  1. #1
    Join Date
    Jun 2005
    Posts
    42
    How dirty should a filter be when it's changed - I change every 2-3 months?

    I use the cheap blue disposable fiberglass filters and there are a few very small dustballs on the filters but otherwise it does not look dirty at all. I switched to the disposable filters because when I used the washable fiberglass or hogshair filters in the past, there was very little dust on those so I thought I wasn't getting enough filtration. But now I wonder if the disposable filters are providing any filtration.

    I'm afraid to move up to the pleated filters - I don't see how air moves through those things.

  2. #2
    Join Date
    Jun 2001
    Posts
    3,910
    You are right that they are providing no filtration. Switch to the pleated disposables. They normally don't last for 3 months as advertized.

    When they are covered with dust, change them. If you can't see light through them, you've waited too long.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    With the filters you are using ,the best filter in the system,is the "wet" coil.Look at Merv 8 or 10 ,4 or5" thick pleated filters.

  4. #4
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    I'm sure you have no clue what the airflow situation is for your system Joe. As such you should think twice before putting in a high efficiency filter. High efficiency is a code word for restrictive. Look at the paper filter and then look at the fiberglass. You can almost see through the fiberglass. The fiberglass breathes much better. Most duct systems are undersized and don’t allow enough air to flow. Put in a high efficiency filter and you could be making a bad situation worse.

    The fiberglass filters are more than adequate to protect the system if installed correctly (no air bypassing, etc.). Most furnace manufacturers provide filters with their furnaces that are similar in efficiency to fiberglass. If fiberglass weren't good enough then I don't think the OEMs would be providing similar efficiency filters with their units. I like higher efficiency filters as much as the next guy. But a system must be designed with them in mind or the airflow will suffer. Cookie cutter and even most custom homes virtually never have duct systems designed to handle high efficiency filters. Adequate airflow is much more important than the mostly placebo effect provided by high efficiency filters.

    As far as the amount of dirt on the filter goes, it's not uncommon for some homes to see very little dirt accumulate. If your return (suction, intake, etc.) vent is high on the wall or ceiling then it may not be getting that much dirt. Dirt tends to hang low. Floor returns will dirty up the filter many times faster.

  5. #5
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,189
    Fiberglass filters in my home work. Evap coil cleaned annually and not much comes off.

    It all depends on your particular duct design and filtering desire. The air velocity is low enough at my filter that the fiberglass filters do a fine job. Of course, I'm just protecting the equipment. I'm not trying to capture every dust and pollen particle.

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    If a system has a ducted return,a lot of "stuff' will collect there before getting to the coil.


    If the return grilles are in the ceiling ,a lot settles in the home,before getting to the filter.


    If you have a furnace,a lot of stuff collects on the blower whell,before getting to the coil,not true with an air handler.

    If you vacuum a lot ,with a cheap vacuum cleaner,more small particles will get into the system.


    Lanced fin coils ,will collect more stuff.

    Fins are spaced closer on newer coils,then older ones.


    Lots of variables,and a merv 8 or 10 ,will handle keeping th coil cleaner longer,saving energy in the process.


    Looking at a coil,is not a good way to tell if it's PD has increased increased .If you are not testing the PD of the coil ,compared to factory specs or previous results ,you really don't know if the coil is restricting the air flow.


    Some manufacturers now sell and recommend,pleated filters.They also built coil with fixed metering devices,does that mean they never thought a TXV is a better way??

  7. #7
    Join Date
    Jun 2005
    Posts
    42
    Thanks for all the replies.

    Had a thought - what exactly (or roughly) equals "one month" in filter usage time. Is it 30 days x 24 hours?

    I just realized we have had a mild May/June here in Ga so the a/c only runs 6-7 hours a day (we turn it off when going to bed and don't turn it back on until mid afternoon). The filter has been in since March (got a little bit of time in during the heating season) but we barely ran the system during the spring.

  8. #8
    Join Date
    Jun 2005
    Posts
    42
    BTW - I do have floor returns on the first floor but it's mostly wood floors (don't know if that increases or decreases dirt into the system but a few of the return grills have dust on them). Upstairs the returns are in the ceiling so that might explain why the upstairs filters are clean.

  9. #9
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Originally posted by joeyjoey
    BTW - I do have floor returns on the first floor but it's mostly wood floors (don't know if that increases or decreases dirt into the system but a few of the return grills have dust on them). Upstairs the returns are in the ceiling so that might explain why the upstairs filters are clean.

    Exactly.

  10. #10
    Join Date
    Oct 2003
    Location
    34.8n 102.4w
    Posts
    3,244
    If you can see thru it, dirt can go thru it.IMO, put in a pleated type at the very east.

    Of course , we live in rural farm and ranch country... lots of "dust" Maybe you city boys don't have that problem ??
    Life goes on long after the thrill of living is gone.

  11. #11
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    There's better and there's adequate Dash. In the case of a TXV the TXV doesn't cause other problems. It's only better while the fixed metering device can be adequate. In the case of filters though better can cause airflow problems. And since airflow problems are rampant, one must assume that a better filter will worsen the problem until a pro can analyze the situation to know that it won't worsen the problem.

    I have no problem with better filters. In farm country they're almost mandatory. But to blindly recommend them to all that come on this board is folly. I'm not saying that you are blindly recommending them. But I sure as sh** haven't seen anything else... yet.

  12. #12
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Sure as ---- ,I think they are needed.
    If mfrs. were worried about keeping coils clean ,and airflow up to the required cfms,why do the include cheap filters that you can see thru??


    Dopes air flow need to be addressed ,absolutly!!!!That's what HVAC contractors should be able to do !!!!

    [Edited by dash on 06-27-2005 at 09:55 AM]

  13. #13
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    Originally posted by dash
    If mfrs. were worried about keeping coils clean ,and airflow up to the required cfms,why do the include cheap filters that you can see thru?
    Because they know that in most applications the see through filters are perfectly adequate for the equipment's sake.

    A great analogy is the much hyped 3000 mile oil change. It's purely an invention of the oil industry. Few cars need their oil changed that often. GM's oil light system often goes off at five to seven thousand miles. Mercedes' OLS can go ten to twenty thousand miles before going off. The 3,000 mile fallacy has been pushed to sell oil and service.

    The same goes for filters. The move towards better filters in the retail segment is largely the result of a desire for higher revenues. My local Home Depot has a wide variety of expensive filters at ground level. They've got a hit and miss selection of fiberglass sitting up high. At one to two dollars a pop versus five to fifteen bucks a pop, there's little question as to why. And it's not because it helps the equipment. Given how starved most HVAC equipment is for air they do their customers a disservice.

    But at least with the oil change no harm is being done. The same can't be said of high efficiency filters.

Page 1 of 2 12 LastLast

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