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  1. #1
    Join Date
    Aug 2011
    Location
    Iowa
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    25

    Static pressure testing

    Just wondering how many techs check static pressures on systems in the homes we are servicing.
    How important is it?

  2. #2
    Join Date
    Jun 2010
    Location
    Danbury Ct 1/2 hour from NYC
    Posts
    204
    I think its one of the most important things, you can have everything else correct but if your airflow and cfm's are not proper your systems not proper. That can be the biggest reason for fan motor problems, balancing and airflow problems, you have to have that right in order for everything else to be right. Good luck charging and servicing a unit properly with static pressure issues!!

  3. #3
    Join Date
    Oct 2011
    Location
    between here and over there
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    453
    I try to on any call I can just because I am trying to learn how to understand airflow and how it effects the system.

  4. #4
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    I agree with Air Movers, it is one of the most important things to check.
    At the very least, it needs to be checked and documented when the equipment is first started up, or the first time you service a system you haven't been to before.
    I also note the ESP, blower speed, CFM, supply static and return static on the equipment with a marker.
    That way I have baseline readings to compare it to if I have to troubleshoot a problem later on.

    Judging by the complete lack of test holes in literally every system I see, that hasn't been serviced by us before, the percentage of people in my area actually checking static pressures, or even getting the most basic evaporator entering air temperatures needed for correct charging, is very low.
    If more government is the answer, then it's a really stupid question.

  5. #5
    Join Date
    Apr 2012
    Location
    Millsboro, DE
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    100
    I think it's a topic many contractors don't want to know about: They've always used 500 SF/Ton and 0.10"/100 feet and they've "never had a problem".

    It's good to see people who think otherwise, may your tribe increase.

  6. #6
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by ferd1942 View Post
    They've always used 500 SF/Ton and 0.10"/100 feet and they've "never had a problem".
    Yeah, if you never actually test anything, of course you "never had a problem".
    If more government is the answer, then it's a really stupid question.

  7. #7
    Join Date
    Jul 2011
    Location
    East coast USA
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    964
    Quote Originally Posted by Zippy4god View Post
    Just wondering how many techs check static pressures on systems in the homes we are servicing.
    How important is it?
    I would say on a routine maintenance inspection Never. And most of the time techs will not check SP across the evap. Over all if you have a steady customer its good to check and to keep records. yes SH, SC and pressures can tell you a lot but SP is good to know.

  8. #8
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    5,519
    Let me tell you why static tests aren't that important.
    A fan curve is plotted from laboratory test data under ideal conditions with NO inlet restrictions.
    Not every fan is tested. Similar fans have curves developed by interpreting
    test data.
    Sometimes they are useful as a design tool
    They represent laboratory data and do not represent measurable performance under field conditions.
    They can be useful in trying to get a probable performance of a fan type.
    You cannot predict the CFM of a fan from lab data because it'd difficult to predict system effect.

    This information was gleaned from T&B data of the Sheet Metal and Air Conditioning Industry.
    I've always thought that too much emphasis has been placed recently on static testing to the point of replacing real T&B instrument testing.
    On T&B reports, static tests were made to inform the engineer but the numbers that really matter are the actual real world performance measurments.
    Tracers work both ways.

  9. #9
    Join Date
    Jul 2011
    Location
    East coast USA
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    964
    Quote Originally Posted by hvacker View Post
    Let me tell you why static tests aren't that important.
    A fan curve is plotted from laboratory test data under ideal conditions with NO inlet restrictions.
    Not every fan is tested. Similar fans have curves developed by interpreting
    test data.
    Sometimes they are useful as a design tool
    They represent laboratory data and do not represent measurable performance under field conditions.
    They can be useful in trying to get a probable performance of a fan type.
    You cannot predict the CFM of a fan from lab data because it'd difficult to predict system effect.

    This information was gleaned from T&B data of the Sheet Metal and Air Conditioning Industry.
    I've always thought that too much emphasis has been placed recently on static testing to the point of replacing real T&B instrument testing.
    On T&B reports, static tests were made to inform the engineer but the numbers that really matter are the actual real world performance measurments.
    i agree with what you say in the most part. But when you come upon a system you never worked on, SP is good information to to have. Like whats the pressure drop across the coil or filters, whats the SP at the farthest point in the duct run

    In a VAV system, using bypass dampers or VFDs or vortex dampers ect..SP becomes more important. Taking the time to understand pressures is another slice of the pie you shouldn't leave out.

    when you go to a job the customer is not waiting there with the last T&B for you to read. Its nice to check a few spots with a electronic manometer. You may be surprised what you find.

  10. #10
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,967
    Quote Originally Posted by hvacker View Post
    Let me tell you why static tests aren't that important.
    A fan curve is plotted from laboratory test data under ideal conditions with NO inlet restrictions.
    Not every fan is tested. Similar fans have curves developed by interpreting
    test data.
    Sometimes they are useful as a design tool
    They represent laboratory data and do not represent measurable performance under field conditions.
    They can be useful in trying to get a probable performance of a fan type.
    You cannot predict the CFM of a fan from lab data because it'd difficult to predict system effect.

    This information was gleaned from T&B data of the Sheet Metal and Air Conditioning Industry.
    I've always thought that too much emphasis has been placed recently on static testing to the point of replacing real T&B instrument testing.
    On T&B reports, static tests were made to inform the engineer but the numbers that really matter are the actual real world performance measurments.
    It is good to see someone mention system effect. The way so many residential duct systems are designed... I would love to see a field study of actual measured air flow of a large amount of systems to see how far off most of them are as compared to their blower performance charts.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  11. #11
    Join Date
    Apr 2012
    Location
    Jamestown NC
    Posts
    10
    What are some of the tools you are using to check for proper static? digital versus mag
    nehelic, etc..

  12. #12
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    5,519
    Quote Originally Posted by Central NC Tech View Post
    What are some of the tools you are using to check for proper static? digital versus mag
    nehelic, etc..
    I use an Alnor velometer with a static probe. Because I don't consider the TSP to be as important as actual air flow measurements almost any instrument such as a magnehelic or a manometer would be ok.
    A lot of emphasis is placed on static measurements by the manufacturers of test equipment. Some make it sound like a one tool fits all and this is all you need. I doubt anyone with a T&B cert would agree with this.
    Tracers work both ways.

  13. #13
    Join Date
    Jan 2007
    Location
    Mn the state where absolutey nothing is allowed
    Posts
    1,351
    Quote Originally Posted by hvacker View Post
    I use an Alnor velometer with a static probe. Because I don't consider the TSP to be as important as actual air flow measurements almost any instrument such as a magnehelic or a manometer would be ok. A lot of emphasis is placed on static measurements by the manufacturers of test equipment. Some make it sound like a one tool fits all and this is all you need. I doubt anyone with a T&B cert would agree with this.
    will you please rephase your second sentence. its a little unclear. thank you very much.....

    i am very much interested in air flow measurement and have also seen many inconsistances (sp) reguarding tesp vs capacity checks and also dipswitch settings vs. ecm motors/ cfm
    my boss thinks its possible to repeal the laws of physics

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