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Thread: Filters

  1. #1
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    Filters

    How restrictive of a filter do you recommend to your customers? Obviously, from an equipment standpoint, the less restrictive the better. However, I keep running into customers that want 5" filters that are MERV 13. My perspective is if you put it in new and you can hear the motor change, it's too restrictive. Thought I'd get some more perspective though

  2. #2
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    Quote Originally Posted by acescc View Post
    How restrictive of a filter do you recommend to your customers? Obviously, from an equipment standpoint, the less restrictive the better. However, I keep running into customers that want 5" filters that are MERV 13. My perspective is if you put it in new and you can hear the motor change, it's too restrictive. Thought I'd get some more perspective though
    Not a fan of the 3m filtretes

    Also I don't base restrictions on audible sounds. Run an eternal static pressure test with various filters on your own system and find out what you like best..

    Let the numbers tell you which is better or worse

    Sent from my LM-G710VM using Tapatalk

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  4. #3
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    It all depends on what static 'budget' is available for the filter. Remove the filter and take an external static reading to see what you're dealing with.
    Most filter manufacturers will have charts for their different filters to show what the initial pressure drop is versus cfm and velocity.

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  6. #4
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    Thread Starter
    We've had to start warning some of our customers not to use the "purple" filtrete filters because they're too restricitive. Especially with the new Carrier furnaces matched with the N coil. They tend to burn to hot regardless of filter though...

  7. #5
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    Last summer a friend put in his own 1"pleated filter. I got the "Bat Signal " for a "no AC call" only after the evap froze over. The duct was so crappy that the pleated filter caused an air flow restriction which dropped the suction below freezing. So, during the AC season that is my judgement line.

  8. #6
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    As long as the TESP is below 0.80 in. w.c. and the blower is moving the right amount of airflow, I don’t care what the customer uses. But in most situations where the return is way undersized, rock-catchers up to MERV 6 are what I recommend.

  9. #7
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    There are two goals for the filter size:

    1) large enough surface area to have low static, and

    2) the size reduces the face velocity.

    It is a good idea to put in a large filter rack...larger than the return itself where possible...and allow for a thicker filter like a 2" or 4" to keep the resistance to airflow very low (it will increase during the time before filter change) and the air velocity is lower where the air passes through the filter medium.

    Most 1" filters will be detrimental to the system.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  10. #8
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    All of the above. And if you can only fit a 1", go as cheap as possible. No pleated, cheap blue hoghair.

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  12. #9
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    when a customer askes, I typically respond: What is it you are trying to accomplish? Do you have allergies and other health issues, because better, thicker, more restrictive filters do not mean better indoor air quality unless you are willing to upgrade other aspect of your HVAC system. For most application I recommend staying with the normal blue fiberglass filters.

    Depending on what they say directs the rest of the discussion

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  14. #10
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    The filter is there to keep the evaporator clean. When people ask about cleaner air for health issues, I mention the special equipment that Extreme Makeover Home Edition installed many years ago for an immune compromised child. It cost many tens of thousands in upgrade costs. I explain if you have a high end Mercedes, can probably afford that kind of system, but you might have to sell some stock.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

    AOP Forum Rules:







  15. #11
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    I always suggest a quality brand of EAC. Virtually zero air flow restriction and consistently effective between cleanings while being almost 100% efficient at cleaning the air. Hell; the ones in my house will take visible cigar smoke out of the air stream.

    PHM
    --------


    Quote Originally Posted by acescc View Post
    How restrictive of a filter do you recommend to your customers? Obviously, from an equipment standpoint, the less restrictive the better. However, I keep running into customers that want 5" filters that are MERV 13. My perspective is if you put it in new and you can hear the motor change, it's too restrictive. Thought I'd get some more perspective though
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  16. #12
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    I stay away from the expensive pleated and washables... cheap pleated, or cheap fiberglass disposables. Unless there is multiple filter grills with plenty of surface area, then I would consider slightly more restrictive pleated ones.

  17. #13
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    In my own home I use a cheapy 1" spun glass as a pre filter, then a 1" pleated. You'd be amazed how the cheapy spun glass filter catches so much. Pleated only gets changed once every few years.
    I do a triple evac with nitro to remove non condensables.

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