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  1. #14
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    Aug 2004
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    North Richland Hills, Texas
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    There is a relatively simple way to do good performance checks of systems without connecting gauges, but you need to be able to measure the airflow through the indoor unit.
    Checking what is coming out of the registers with a flow hood doesn't count, and is often very inaccurate anyway.

    Testo has a lot of details on it in their AC/R Application Guide.
    They took down the page where it could be downloaded off their site, but I have it stashed on mine.
    http://www.markbeiser.com/HVAC/docum...Guide_2007.pdf

    I hadn't previously linked to it on my site because Testo had people filling out a form before downloading it. Now that the form and download link are gone off Testo's site, I'll keep it on mine. At least until I see it available for download from Testo again, or someone from Testo asks me to remove it.
    If more government is the answer, then it's a really stupid question.

  2. #15
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    Aug 2003
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    Central Kentucky
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    Quote Originally Posted by mark beiser View Post
    There is a relatively simple way to do good performance checks of systems without connecting gauges, but you need to be able to measure the airflow through the indoor unit.
    Checking what is coming out of the registers with a flow hood doesn't count, and is often very inaccurate anyway.

    Knowing fan airflow is one thing knowing actual delivered airflow from the system is another.

    Checking what is coming out of the grilles is a huge part of what it is about as the delivered airflow determines the true efficiency.

    Flow hood measurements can be a very accurate way to measure delivered airflow, the hood type is a big determining factor in accuracy.
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  3. #16
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    Quote Originally Posted by davidr View Post
    Knowing fan airflow is one thing knowing actual delivered airflow from the system is another.

    Checking what is coming out of the grilles is a huge part of what it is about as the delivered airflow determines the true efficiency.
    True, but for doing an equipment capacity check and gaugeless refrigerant charge check, it is only the actual airflow at the equipment that is needed, and a flow hood won't tell you that.

    Flow hood measurements can be a very accurate way to measure delivered airflow, the hood type is a big determining factor in accuracy.
    If you consider "very accurate" to be +/-20%, or more, then sure....

    The only hood type that is "very accurate" is the active type of hood, which I haven't even seen offered for sale commercially.

    The regular commercially available hoods range from inaccurate to extremely inaccurate for use on residential systems.

    Check out Lawrence Berkeley National Laboratories study on flow hood accuracy on residential systems.
    http://www.osti.gov/bridge/servlets/...ive/791782.PDF


    Having said that, being off by 10-20% on airflow measurements doesn't have a huge impact on the capacity calculations.

    IMO, flow hoods have far to great a margin of error to be used to compare to the measured airflow at the equipment to determine duct leakage and efficiency loss, and you can forget about dialing in exact room by room airflows, lol.
    If more government is the answer, then it's a really stupid question.

  4. #17
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    Aug 2007
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    Quote Originally Posted by RebateReviewer View Post
    thanks for the input everyone. a little about myself I do have Universal Refrigerant Liscence...but have been involved in other areas for some time know. I did start up and PM at the apprentice level in the later 90's....so i do know a thing or two.
    Since when did a government mandated certification become a lisence (sic).

    I've become leery of anyone you uses that line as their claim to "know a thing or two".

    With a few bucks and a short guide my Grandmother can get "certified".

    Looking for short cuts eh, not surprised here.


    Expect nothing, yet expect the unexpected.
    Press on Regardless, Endeavor to Persevere.

  5. #18
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    Jun 2004
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    Howell, Michigan
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    Quote Originally Posted by Snoring Beagle View Post
    Since when did a government mandated certification become a lisence (sic).

    I've become leery of anyone you uses that line as their claim to "know a thing or two".

    With a few bucks and a short guide my Grandmother can get "certified".

    Looking for short cuts eh, not surprised here.

    LOL................my 11 year old could most likely get Universally Certified after 15 minutes of study. It means nothing regarding competency.

    FWIW, a long time ago there was a thread in the ProTech Forum re' checking charges etc without guages.

  6. #19
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    Central Kentucky
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    Quote Originally Posted by mark beiser View Post



    If you consider "very accurate" to be +/-20%, or more, then sure....

    The only hood type that is "very accurate" is the active type of hood, which I haven't even seen offered for sale commercially.

    The regular commercially available hoods range from inaccurate to extremely inaccurate for use on residential systems.

    Check out Lawrence Berkeley National Laboratories study on flow hood accuracy on residential systems.
    http://www.osti.gov/bridge/servlets/...ive/791782.PDF


    Having said that, being off by 10-20% on airflow measurements doesn't have a huge impact on the capacity calculations.

    IMO, flow hoods have far to great a margin of error to be used to compare to the measured airflow at the equipment to determine duct leakage and efficiency loss, and you can forget about dialing in exact room by room airflows, lol.

    Lol.....Of all the studies to quote.
    I've had a copy of that study for some time and still find it as ludicrous today as I did back then.
    These are the same guys who think that you can use trash bags and laundry baskets for flow hoods as well.

    Sit back and really read that report sometime, the base flow hood was their active flow hood that the whole report was based on.
    They used the flow hood they made with a duct blaster and cardboard as the standard for rating the commercial flow hoods!
    Then they publish a report telling everyone that the flow hoods are off up to 20% based on this?

    Maybe instead of trying to give flow hoods a black eye the LBNL guys should learn how to use them properly first.

    Those flow hoods that are being questioned will give more accurate results than a blower door will give on natural infiltration values.
    That is unless the results are being compared to an Alnor Lo-Flo hood which needs the addition of correction factors to compensate for the short skirt design.

    Like I said in my first post knowing the fans airflow is one thing knowing the delivered airflow is another.

    If someone is using the equipments capacity as an indicator of what the total system is doing the results will be off at best.
    The duct system is going to determine the efficiency of the equipment more than the equipment will.
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  7. #20
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    Mar 2005
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    Suppy NC
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    it would seem to me that as long as they turn in a manJ load calc and a start up sheet then you only have to verafy that the equipment matches the load.

    as long as the equipment fall into the delta-t requirements as set by the program you offer your job is done.

    there is no reson to second guess you certified contractors as this will be cause for all coustomers to question the program and contractors knowlege


    it would seem your job is to certify the model # and serial# temps and does the equipment match the load calcs. Also to verify that the equipment meet the rated seer or eficency as stated by the guidelines in the contract of the program. Coil matches condenser and line set is correct size for the unit. Blower size is correct as per model #

    the rest is the contractors job to make sure it is charged and running correcty.

    a random spot check is ok to watch as the contractor sets up the unit as this shows the costumer everyone is one the ball

    JMHO

  8. #21
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    Jun 2007
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    Round Rock
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    I believe the answer to this question and to prevent lots more posts on the subject is a resounding NO. There is no quick way to check it. If you have an approved list of contractors that met all your qualifications and the homeowner used them, then that should be good enough. If not, too bad. You can pay the contractors to come out and show you. Otherwise, cough up the $$$ for the rebates and move on. You cannot use the split method to determine proper install. What if it is running on low speed? You'll be wasting precious time of contractors with better things to do than chasing around some pencil pusher who thinks they know more than they do. We get it all the time, it usually amounts to a waste of 3 hours of my time when some inspector doesn't know squat and I have to show him.

  9. #22
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    Apr 2007
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    6,285
    Quote Originally Posted by RebateReviewer View Post
    As far as this program is concerned the Utility Company has a qualified contractor list, to be on this list contractors must pass 3 classes (Load Calc, Refrigerant Charge, and Airflow)...then they and their customers are eligeable to receive an additional incentive beyond the incentive for just purchasing high efficient equipment....

    Yeah but what company is going to provide an "additional rebate or service" and not require some sort of quality control......besides the government. This is a program I bet tot aim towards being greener and leaving the power company in a better situation to have to avoid things like brown outs and having to buy power from other states.

  10. #23
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    Aug 2007
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    Just had a thought... (owww)

    What if Mr. rebate reviewer didn't ask the right question, (ahem).

    Could refrigerant charge be the juice installed?

    R-22 vs R410a.

    This would fit the politically correct qualification.


    Expect nothing, yet expect the unexpected.
    Press on Regardless, Endeavor to Persevere.

  11. #24
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    Quote Originally Posted by davidr View Post
    Sit back and really read that report sometime, the base flow hood was their active flow hood that the whole report was based on.
    They used the flow hood they made with a duct blaster and cardboard as the standard for rating the commercial flow hoods!
    Then they publish a report telling everyone that the flow hoods are off up to 20% based on this?
    You should read the report.
    The active flow hood was used as the reference in the field testing because it was so accurate in the laboratory tests, nothing wrong with that.

    These guys don't have a "dog in the hunt" as far as products to sell, our tax dollars at work.

    The trash bag and laundry basket methods you mentioned are not as ridiculous as they sound, but would look to unprofessional to use, lol.

    If you know the volume of the big bag, and can accurately measure the time it takes to fill up, cfm from a register can be accurately calculated.

    If you know the area of all the openings in the laundry basket, or box with holes cut in it, and can measure the static pressure drop between the inside and outside of the basket/box, airflow can be calculated.
    If more government is the answer, then it's a really stupid question.

  12. #25
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    Quote Originally Posted by mark beiser View Post
    You should read the report.
    The active flow hood was used as the reference in the field testing because it was so accurate in the laboratory tests, nothing wrong with that.

    These guys don't have a "dog in the hunt" as far as products to sell, our tax dollars at work.

    The trash bag and laundry basket methods you mentioned are not as ridiculous as they sound, but would look to unprofessional to use, lol.

    If you know the volume of the big bag, and can accurately measure the time it takes to fill up, cfm from a register can be accurately calculated.

    If you know the area of all the openings in the laundry basket, or box with holes cut in it, and can measure the static pressure drop between the inside and outside of the basket/box, airflow can be calculated.

    I have been through that report with a fine tooth comb Mark, I know it well.

    You are a sharp guy Mark, one of the sharpest on this site take that report and really look at the fundamentals of a powered flow hood don't just take what LBNL wrote at face value without really looking at it. There is a lot more to it than what that report addresses, look deep enough and you will find it.

    The whole concept of a powered flow hood violates every fan law ever addressed by ASHRAE.
    The trash bag and laundry basket would be even worse, talk about a unidentifiable back pressure.

    I have a huge problem with someone taking a flow hood built by their own design and then declaring it the most accurate of all tested by their own design criteria, a little suspicious at best.
    We would crap and raise three kinds of hell if any manufacturer dared to do that with the efficiency ratings of a piece of equipment they designed but find it perfectly acceptable for the folks at LBNL to follow this practice?

    As far as those guys "not having a dog in the hunt", I wouldn't be so sure of that.

    Like I said before Mark you are a sharp guy, I love your post but that active flow hood is not commercially available for a reason.
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  13. #26
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    Dec 2006
    Location
    toronto, canada
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    551
    If you happen to check a lennox unit, you may be lucky to check the charge without gauge because some lennox use approach temp=liquid temp-oat to measure the charge.

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