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Thread: HRV performance number seem too high

  1. #1
    Join Date
    Oct 2020
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    HRV performance number seem too high

    Had a fan tech flex 100 HRV installed
    Testing with manometer to balance gives exhaust of 92 pa and intake of 99 pa regular speed and 66 pa exhaust and 69 pa intake on reduced speed
    With 4 ducts my calculations seem to convert this to cfm of
    Regular ex 213 cfm in 221 cfm
    Reduced ex 180 cfm in 185 cfm

    despite the machine being rated at 100pa=122 cfm by the brochure

    can anyone explain or assist with this please
    Tks

  2. #2
    Join Date
    Jan 2015
    Location
    San Diego, CA
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    592
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    Can you explain and show your calculation going from pa to cfm?

  3. #3
    Join Date
    Feb 2016
    Location
    Louisburg Kansas
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    4,915
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    You lost some replies. Your CFM calculation does not give the actual airflow. Your calc gives the system curve but assumes the statics are developed by CFM. The fan can't do that so your CFM is a lot lower than you calculated.
    No man can be both ignorant and free.
    Thomas Jefferson

  4. #4
    Join Date
    Jan 2015
    Location
    San Diego, CA
    Posts
    592
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    Looks like the op is creating multiple threads on the same topic.

    https://hvac-talk.com/vbb/showthread...-seem-too-high

    and a couple of others

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