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  1. 07-18-2008, 12:45 AM #1
    mknox
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    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...
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  2. 07-18-2008, 12:51 AM #2
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    beenthere
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    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. 07-18-2008, 12:55 AM #3
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    iraqveteran
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    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.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.
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  4. 07-18-2008, 01:07 AM #4
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    beenthere
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    Outdoor DB.
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  5. 07-18-2008, 06:19 PM #5
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    Same here. I use that formula, unless I have a manufacturers chart to go by.
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  6. 07-18-2008, 06:20 PM #6
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    aintitfun
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    Do you guys take wb at return and supply and then average them?
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  7. 07-18-2008, 06:36 PM #7
    badboyheel
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    is there a rule of thumb SH? i've read nothing below 8 and nothing above 30 true?
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  8. 07-18-2008, 06:57 PM #8
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    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.
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  9. 07-18-2008, 06:58 PM #9
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    cmajerus
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    if it's in the unit I use that, otherwise I use Trane's sliderule.
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  10. 07-18-2008, 08:00 PM #10
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    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.
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  11. 07-18-2008, 08:20 PM #11
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    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?
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  12. 07-18-2008, 08:26 PM #12
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    mikelcs
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    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
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  13. 07-18-2008, 08:29 PM #13
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    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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