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  1. #1
    Join Date
    Mar 2005
    Location
    reading PA
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    20

    target superheat

    so ive seen a number of target superheat charts around but am wondering a calculation ive recently stumbled upon. wet bulb times 3,minus 80, minus outdoor ambient temp.. just wondering if most use a standard chart, try and go by what is on/in the odu, or mabey this calculation? any input is welcome...

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,120
    If the unit has a charging chart I use it.
    If it doesn't and its a fixed metering device, I use that formula.
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  3. #3
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Do you use outdoor DB or WB?
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    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

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  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,120
    Outdoor DB.
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  5. #5
    Join Date
    Apr 2007
    Posts
    623
    Same here. I use that formula, unless I have a manufacturers chart to go by.

  6. #6
    Join Date
    Apr 2007
    Posts
    623
    Do you guys take wb at return and supply and then average them?

  7. #7
    Join Date
    Mar 2008
    Posts
    657
    is there a rule of thumb SH? i've read nothing below 8 and nothing above 30 true?
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  8. #8
    Join Date
    Apr 2007
    Posts
    623
    Quote Originally Posted by badboyheel View Post
    is there a rule of thumb SH? i've read nothing below 8 and nothing above 30 true?
    It all depends on wb, and ambient , use the formula, if you do not take into account the wb (which factors in the humidity) you will be way off, 8-30 is a very broad range.

  9. #9
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,677
    if it's in the unit I use that, otherwise I use Trane's sliderule.
    You can't fix stupid

  10. #10
    Join Date
    Apr 2007
    Posts
    623
    Quote Originally Posted by cmajerus View Post
    if it's in the unit I use that, otherwise I use Trane's sliderule.
    I am pretty sure, and you can check this, but I have a slide rule from Amana, And if I use the formula , I come up with the same #s as it does , But you have to start with Knowing your target SH, On the one I have.
    Last edited by aintitfun; 07-18-2008 at 08:19 PM.

  11. #11
    Join Date
    Apr 2007
    Posts
    623
    Quote Originally Posted by aintitfun View Post
    Do you guys take wb at return and supply and then average them?
    Anyone have an answer to this one?

  12. #12
    Join Date
    Feb 2007
    Location
    Dallas, Tx.
    Posts
    572
    Quote Originally Posted by aintitfun View Post
    Anyone have an answer to this one?
    return only, I'm not sure why you would need it at the supply.
    also- if you do take supply wetbulb too close to the coil, it will read close to drybulb.
    mike

  13. #13
    Join Date
    Apr 2007
    Posts
    623
    Quote Originally Posted by mikelcs View Post
    return only, I'm not sure why you would need it at the supply.
    also- if you do take supply wetbulb too close to the coil, it will read close to drybulb.
    seems like I have heard others say they take both and then average them to account for "mixing" I have just been doing return only, but tested a few by averaging, not a huge difference but about 2-3 degrees between methods. What is your theory of reading close to db if close to coil?

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