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  1. #1
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    Apr 2017
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    Which one is more efficient?

    Is High Velocity more efficient than conventional system?

  2. #2
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    May 2000
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    Indianapolis, IN, USA
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    If you look at SEER ratings, high velocity kills them. That's why they got a loophole around the 13 SEER minimum. There can be cases of a "16 SEER" or higher outdoor unit (matching indoor) that only gets 12 or 13 SEER with a Space Pak or Unico. Also watch capacity, usually end up losing about 1/2 a ton. An 036 might be rated at 30K with a HV air handler.

  3. #3
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    Sep 2007
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    Not quite an answer but...

    The problem I have seen with high velocity is that it does not do well to get rid of humidity. Others may have different experience in different areas of the country.
    Can someone please explain to me -
    Why is there never enough time to do it right the first time, but plenty of time to do it twice?


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  4. #4
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    Aug 2001
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    Quote Originally Posted by joemach View Post
    Not quite an answer but...

    The problem I have seen with high velocity is that it does not do well to get rid of humidity. Others may have different experience in different areas of the country.
    Most systems run about 300cfm/ton and from my experience it is just the opposite, they have far more latent removal and less sensible

    'The more you know, the more you realize you don't know'
    ...

  5. #5
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    Mar 2007
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    When 10 SEER was the norm, high velocity systems only got 9 SEER. When the minimum SEER went to 13, high velocity would only do 10 to 12 SEER. Capacity is almost always lower too. But sometimes there is no room for normal sized ducts, so high velocity is all that you can use. But standard systems are almost always better performing than high velocity systems.
    Remember, Air Conditioning begins with AIR.

  6. #6
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    Nov 2014
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    Chicago Illinois
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    Yeah I have noticed the same thing with Ave last three systems they don’t do very well with removing humidity

  7. #7
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    Aug 2018
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    I saw a unit that said its a Hydrocarbon AC what does that mean? it claims to be 920 watts for 13K BTU

  8. #8
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    Feb 2019
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    The first major difference between high velocity and other types of cooling is how they work. All air conditioners are considered “forced air” units, but the different types rely on certain methods of air circulation.

    Conventional AC systems rely on the method of diffusion, where cool air enters a room through a vent (supply vent), then is drawn back out through another vent (intake vent). Naturally, hot air rises and cold air sinks so the circulation in the room depends greatly on the placement of the supply and intake vents.

    High-velocity AC systems rely on the aspiration method, where the air is delivered with such speed that it creates air currents which circulate the cooled air throughout the room. In addition to creating better circulation, high-velocity air conditioning systems do a great job of reducing humidity.

    Ducting
    air conditioning systemsWith all central air conditioning, ducts are needed to carry the cool air throughout the building. However, certain properties are restricted when it comes to the type of ducting will fit with the architecture.

    Conventional AC systems require metal ductwork that averages about 6″ in diameter. This ductwork runs in two branches for the supply and intake of cool air. All of this ducting does require a significant amount of space. In many cases, some construction is needed to fit the building.

    High-velocity AC systems use smaller, insulated aluminum tubes for ducting. These tubes are flexible and average about 2″ in diameter. Because of the size, these tubes are generally easier to fit into existing walls, floor joists, etc. Many older homes are better candidates for high-velocity AC.

  9. #9
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    Mar 2019
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    Edmonton, AB Canada
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    Quote Originally Posted by BaldLoonie View Post
    If you look at SEER ratings, high velocity kills them. That's why they got a loophole around the 13 SEER minimum. There can be cases of a "16 SEER" or higher outdoor unit (matching indoor) that only gets 12 or 13 SEER with a Space Pak or Unico. Also watch capacity, usually end up losing about 1/2 a ton. An 036 might be rated at 30K with a HV air handler.
    I agree with you in some cases high velocity kills SEER ratings but it entirely based on the total space you are taking benefit. However, if we do proper research on how and when to choose an HVAC system then it can solve many problems. Check seer rating, BTU and other total covered area can enhance the performance of these systems. Use right system in right area..

  10. #10
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    Sep 2002
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    More efficient at doing what?

    If you consider only SEER ratings then: no; High Velocity systems operate outside the standard rating envelope and so do not 'show well'. This is because the tests were not designed around showcasing the HV system's superior points.

    HV systems operate at lower air volume and discharge a much lower air temperature. This allows them to be far superior at removing moisture from the air stream.

    The air ducts are Much smaller and so have lower duct losses.

    In my experience the outdoor unit has to be matched to the cooling load By The Compressor Size - and NOT by the outdoor unit's BTU rating.

    Higher SEER condensing units / systems get those high SEER numbers by using a smaller compressor with large indoor and outdoor coils. This reduces the high pressure of the system and increases the low pressure of the system. The compression ratio of the compressor is lowered and the volumetric efficiency of the compressor is increased - due to a greater suction gas density. It also increases indoor coil temperature - makes it operate closer to the dew point - and so tends to remove less moisture per operating time.

    This 'tricks' the standard compressor rating system somewhat. So a 36,000 BTU condensing unit may have a 29,000 BTU compressor in it.

    The thermodynamics 'trick' does not happen with a HV system as the indoor coil operates at just above freezing. Which is why it removes so much more moisture from the air.

    HV does have in common with LV systems in that BOTH Require Accurate Installation and Initial Setup in order to operate as they were intended to do.

    PHM
    -----------------




    Quote Originally Posted by eshi1362 View Post
    Is High Velocity more efficient than conventional system?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  11. #11
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    Sep 2002
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    This can only be the result of poor set-up.

    The airflow through the evaporator is critical to proper performance. The evaporator needs to operate at just above freezing. This is accomplished by properly adjusting the discharge air damper at initial startup.

    PHM
    ----------



    Quote Originally Posted by joemach View Post
    Not quite an answer but...

    The problem I have seen with high velocity is that it does not do well to get rid of humidity. Others may have different experience in different areas of the country.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  12. #12
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    Sep 2002
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    Maybe I should add that I have installed a bunch of HV systems and have one of my own which heats and cools about half of my house. There is plenty of room for a Low Velocity system - but I'd never trade my HV system for something else. <g>
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  13. #13
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    Jan 2019
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    Quote Originally Posted by john5220 View Post
    I saw a unit that said its a Hydrocarbon AC what does that mean? it claims to be 920 watts for 13K BTU
    Hydrocarbon refers to molecules composed of hydrogen and... You'll never see this one coming... Carbon. Natural gas, propane, and butane are commonly known hydrocarbons.

    While they're commonly combusted to provide their energy content as heat, propane and iso-butane (and probably others that I'm unaware of) are both useful as refrigerant gasses.

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