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  1. #14
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    Jul 2007
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    Virginia
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    Quote Originally Posted by ga-hvac-tech View Post
    Well... it seems to depend which way one learned TESP... I have heard it both ways.
    I think we had this discussion somewhere before, I have forgotten the name of the thread though...
    I sent you an email of a presentation I put together awhile back on TESP testing.

    I would post it here, but I don't post technical info or manuals, in this "OPEN" forum.

    If anyone else wants it, send me an email (address is in my profile).

    Footnote:

    Using a pitot tube in a residential application not only requires you to do math in public, but will require alot of straight duct, before and after the pitot tube, to get an accurate reading.

    Even using the smaller static probes can give inaccurate readings because of turbulent airflow.
    Instead of learning the tricks of the trade, learn the trade.

  2. #15
    Join Date
    Jun 2007
    Location
    Jersey
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    197
    Quote Originally Posted by rundawg View Post
    I sent you an email of a presentation I put together awhile back on TESP testing.

    I would post it here, but I don't post technical info or manuals, in this "OPEN" forum.

    If anyone else wants it, send me an email (address is in my profile).

    Footnote:

    Using a pitot tube in a residential application not only requires you to do math in public, but will require alot of straight duct, before and after the pitot tube, to get an accurate reading.

    Even using the smaller static probes can give inaccurate readings because of turbulent airflow.
    Hey Rundawg, would you be able to send me this info also? Thanks!
    Any fool can know. The point is to understand. Albert Einstein

  3. #16
    Join Date
    Jun 2004
    Location
    Eugene, Oregon
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    1,018
    Has anyone tried to build their own flow hood and use a digital manometer with fpm display to measure airflow? I was thinking of a testo 510 and a 1'x1' square by 6" long piece of sheet metal duct with a pressure sensing grid. The grid would be 1/4" tubing with holes drilled to measure the velocity pressure and a second grid underneath the upper grid to measure the static pressure. Then attaching a homemade hood to the measuring assembly. You could even make the hood from cardboard to funnel the supply air.
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  4. #17
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    Aug 2004
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    North Richland Hills, Texas
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    Quote Originally Posted by air1 View Post
    Has anyone tried to build their own flow hood and use a digital manometer with fpm display to measure airflow? I was thinking of a testo 510 and a 1'x1' square by 6" long piece of sheet metal duct with a pressure sensing grid. The grid would be 1/4" tubing with holes drilled to measure the velocity pressure and a second grid underneath the upper grid to measure the static pressure. Then attaching a homemade hood to the measuring assembly. You could even make the hood from cardboard to funnel the supply air.
    Old trick, works best with a vane anemometer.
    Set the dimensions of the outlet of the box, and do an average velocity reading, the anemometer calculates the CFM.

    On residential grills it can be quite accurate if you use a rectangular box, long enough for the turbulence to mostly settle, and are not choking the airflow down with the box.

    If you look into how shockingly inaccurate the results from expensive flow hoods can be, you may come to a similar conclusion as other people have.
    The anemometer traversing the outlet of a box method is at least as accurate as a $2000+ flow hood, probably more so if done properly.
    If more government is the answer, then it's a really stupid question.

  5. #18
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    Jun 2004
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    Eugene, Oregon
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    Quote Originally Posted by mark beiser View Post
    Old trick, works best with a vane anemometer.
    Set the dimensions of the outlet of the box, and do an average velocity reading, the anemometer calculates the CFM.

    On residential grills it can be quite accurate if you use a rectangular box, long enough for the turbulence to mostly settle, and are not choking the airflow down with the box.

    If you look into how shockingly inaccurate the results from expensive flow hoods can be, you may come to a similar conclusion as other people have.
    The anemometer traversing the outlet of a box method is at least as accurate as a $2000+ flow hood, probably more so if done properly.
    So an anemometer would be better than a average of the velocity pressure?

  6. #19
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    Apr 2012
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    Cleveland
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    Hey run dawg would you be able to send that to me too? Thanks.

  7. #20
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    Aug 2004
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    North Richland Hills, Texas
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    Quote Originally Posted by air1 View Post
    So an anemometer would be better than a average of the velocity pressure?
    Absolutely, because a traverse with an anemometer is a direct measurement of the average air velocity, so there is only one step to calculating the CFM.
    With a vane anemometer, no corrections for air density are needed either.

    You can do it with a pitot tube and manometer, but then you have to convert velocity pressure to velocity, with associated air density corrections, for each measurement point, average them, then calculate CFM.
    The measurements are also MUCH more subject to error due to turbulence than using a vane anemometer.
    If more government is the answer, then it's a really stupid question.

  8. #21
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    Jun 2004
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    Eugene, Oregon
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    Quote Originally Posted by mark beiser View Post
    Absolutely, because a traverse with an anemometer is a direct measurement of the average air velocity, so there is only one step to calculating the CFM.
    With a vane anemometer, no corrections for air density are needed either.

    You can do it with a pitot tube and manometer, but then you have to convert velocity pressure to velocity, with associated air density corrections, for each measurement point, average them, then calculate CFM.
    The measurements are also MUCH more subject to error due to turbulence than using a vane anemometer.
    I was thinking of using a "velogrid" arrangement. A velogrid is effectively a pitot tube that mesures velocity pressures at multiple locations simultaneously. The result is an average velocity pressure of the area being measured. Connecting the velogrid to a Testo 510 would convert the velocity pressure to fpm and if the area is 1 sq. ft. the fpm would equal cfm. The testo 510 has air density compensation capabilities although I'm not sure how one would go about setting it.
    I don't mean to be argumentative. I'm just trying to understand the why a anemometer is better. Personally, I've never trusted vane anemometers. Seems to me that a vane anemometer would be affected by friction caused by wear over time.
    "The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
    "Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
    http://www.campbellmechanical.com

  9. #22
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    Jul 2007
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    Virginia
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    Quote Originally Posted by cuervo View Post
    Hey Rundawg, would you be able to send me this info also? Thanks!
    I would need an email to do that.

    Put an address in your profile, or send me an email (address is in my profile), and I will get it off to you.
    Instead of learning the tricks of the trade, learn the trade.

  10. #23
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    Virginia
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    Quote Originally Posted by cuervo View Post
    Hey Rundawg, would you be able to send me this info also? Thanks!
    double post - sorry
    Instead of learning the tricks of the trade, learn the trade.

  11. #24
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    Virginia
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    Quote Originally Posted by Hvac216 View Post
    Hey run dawg would you be able to send that to me too? Thanks.
    Check your email.
    Instead of learning the tricks of the trade, learn the trade.

  12. #25
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    Jun 2007
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    Jersey
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    Quote Originally Posted by rundawg View Post
    I would need an email to do that.

    Put an address in your profile, or send me an email (address is in my profile), and I will get it off to you.
    Thanks for the info!

    Here's a question............
    If there's no way to pop a hole in the back of a residential furnace (walls or other restrictions) and evaporator coil is right above the furnace, is the limit hole (if centered) an option to take the TESP or is it still too much turbulence from the blower to get an accurate reading? I've never tried this myself.
    Leaving the only choice to popping a hole into the evaporator coil casing.
    Any fool can know. The point is to understand. Albert Einstein

  13. #26
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    Jun 2001
    Location
    Louisville, KY
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    I only drill a hole in the plenum above the coil. I use holes already in the furnace.

    NCI has found that the average difference in pressure between the limit hole and bottom of the coil to be 0.04 IWC.

    I measure return pressure in the thermostat wire hole or the fault code peep hole. Slide the filter out for filter pressure drop.

    Easy breezy.
    Perhaps you should have read the instructions before calling.

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