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Thread: Humidifier Bypass

  1. #16
    DIY Senior Member Hube's Avatar
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    As long as it is installed in the MAIN air stream that is all that matters. Moistened air can be introduced from ANYWHERE within the Main duct stream and still provide humidification to the home.

  2. #17

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    I have mounted them on the A coil housing, on the side facing the flat area of the coil, and high enough not to hit the coil.

  3. #18
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by Hube View Post
    As long as it is installed in the MAIN air stream that is all that matters. Moistened air can be introduced from ANYWHERE within the Main duct stream and still provide humidification to the home.
    Wrong. It will not work well. With the air being 20 F or so colder it is going to have a much lower driving force for humidification. (It will be about half as great at 70 F as at 90 F.) Add to that the problem of 20 F colder air/water interface reducing the effective heat/mass transfer coefficient and less energy available for actually vaporizing water.

    From what I've seen of a properly connected humidifier's performance, connecting one improperly as you suggest would be a waste of time/resources. Might as well not even have it.

  4. #19
    DIY Senior Member Hube's Avatar
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    As long as the Humidifier puts moistened air into the MAIN AIR STREAM and delivers this moistened air into the rooms of the home then it is doing what it was designed to do.

  5. #20
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by Hube View Post
    As long as the Humidifier puts moistened air into the MAIN AIR STREAM and delivers this moistened air into the rooms of the home then it is doing what it was designed to do.
    Doing less than 50% of what it is designed to do is unacceptable.

  6. #21
    DIY Senior Member Hube's Avatar
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    I doubt very much if the performance would be lowered by as much as 50% by not installing it in the most ideal location, but even if it was lowered as much as 50%, the effective amount would still be a lot better than not installing it at all.

    And I still maintain that as long as it is installed within the main air stream it will help increase the humidity within the home.

    Get it ?

  7. #22
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by Hube View Post
    I doubt very much if the performance would be lowered by as much as 50% by not installing it in the most ideal location, but even if it was lowered as much as 50%, the effective amount would still be a lot better than not installing it at all.

    And I still maintain that as long as it is installed within the main air stream it will help increase the humidity within the home.

    Get it ?
    What I get is that you haven't bothered to consider the numbers on relative humidity to get a feel for just how bad an effect this would have. I've seen this sort of mistake made before on analagous systems, passed off with the same reasoning you are applying now.

    However, I neglected to point out another problem. If the bypass is before the coil it will reduce airflow across the coil, thereby reducing the efficiency of the heat pump. Even though the flows to the registers may be the same in the end, the heat pump coil in your scenario will see a reduced flow because you've created an internal bypass stream BEFORE it.

    You've said:
    As I said, it does'nt matter where it is as long as it in the MAIN DUCT AIR STREAM.
    and
    it is doing what it was designed to do
    Neither of which are true.

  8. #23
    Retired Defense Industry Engineer jadnashua's Avatar
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    This is a furnace with a/c, not a heat pump situation, so especially if installed with a damper to shut off that bypass during the cooling season, it would not make all that much difference where it was tappped in. Yes, you will get more vapor per pass if the tap is into hotter air. If you locate the sensor well, you can control this.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #24
    DIY Senior Member Runs with bison's Avatar
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    The issue being discussed at this stage was the placement on a heat pump system. That's what SteveW correctly pointed out and Hube disputed.

    I don't really need the sensor in mid winter. With temps running below 10 F daily average for a week the humidity dips down to the mid 20% range with the humidistat set to call for water the whole time. I can tell by touching both sides of the bypass piping that the evaporation is cooling the bypass gas stream greatly. It would barely work at all if it had zero preheating.

    I won't claim the house is tight, but it is considerably tighter than when I moved in.

  10. #25
    DIY Senior Member Hube's Avatar
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    At least the Moderator(Jadunashua) got it right...."we are not talking about a heat pump system at all.
    But even if it was a heat pump forced air system it can be installed any where on either the return air or the supply air plenums or main trunks.
    Also,the fact still remains that if the Humidifier is allowed to put air into the main air stream no matter where the by-pass is located, the home will still have humidified air injected into it via the supply ducts,etc
    Now do you get it?
    Last edited by Hube; 01-14-2010 at 05:52 PM.

  11. #26
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    You still don't get it. The flowsheeting and heat/material balance issues have escaped you.

    One could do the same thing by putting a bypass takeoff loop in between the furnace exchanger and blower. And it wouldn't work as designed (contrary to your opinion.) Where the humidifier bypass is connected does matter. Just anywhere won't cut it.

  12. #27
    DIY Senior Member Hube's Avatar
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    been there, done that.
    Obviously you have not.

  13. #28
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    Quote Originally Posted by Hube View Post
    been there, done that.
    Obviously you have not.
    That explains your defense of a poorly considered installation. It is one that WILL reduce the efficiency of the units, both for humidifying and for heating.

  14. #29
    DIY Senior Member Hube's Avatar
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    Again, as long as it is installed anywhere within the systems main air stream it will help to raise the humidity within the home.

    (this is a recording....recording,...recording, recording ..etc,etc...

  15. #30
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by Hube View Post
    Again, as long as it is installed anywhere within the systems main air stream it will help to raise the humidity within the home.

    (this is a recording....recording,...recording, recording ..etc,etc...
    So will hanging a wet towel on a rack... The point is it is a lousy way to do it.

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