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  1. #1
    Join Date
    Dec 2012
    Location
    columbus, OH
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    2,042

    Refer cycle queston?

    Fixed metering device system. On a hot day superheat will be higher than a cool day right? My school book says lower and my teacher says its wrong. It makes sense to me it would be higher and im sure he has seen this a 1000 times in the field and the book i want to remove all doubt. Thanks

  2. #2
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,247
    Not necessarily. Lower temps mean lower head which means less refrigerant flowing through the metering device. Slide chart can go as high as 45* ( although comp manufacturers may want 20*) on cool days depending on indoor conditions.

    http://www.hvacsalesandsupply.com/Li...20Charging.pdf
    I carry a gun because I'm too young to die, and too old to take an ass whoopin

  3. #3
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,042
    Thank you duckman the chart really helped.Between fixed bore and TXV and low load and high load,overcharge and undercharge, out door temps, restricted line blah blah blah trying to learn this SH SC thing is really making my head spin. Do you have anymore useful links on this sight or elsewere you would be so kind to share?

  4. #4
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,247
    If you look on the Sporlan site, you can find more info than I could ever help you with for TXV and other refrigerant controls. As far as SH and SC, most manufacturers will provide that info in their IOM's. If you have anything specific, I have tons of manuals I can post for you. Just let me know what you need.

  5. #5
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,042
    No specifics just trying to wrap my head around the whole process how 1+1=2 thank you ill check out sporlan

  6. #6
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,247
    Nice fish btw
    I carry a gun because I'm too young to die, and too old to take an ass whoopin

  7. #7
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,042
    41.5"

  8. #8
    Join Date
    Jun 2004
    Location
    Olean, NY
    Posts
    1,449
    I'll add that on a cool day the refrigerant will have less velocity through the evap. With less back pressure shoving it towards the compressor it has more time to suck up heat from the coil. Thinking of the compressor as positive displacement probably helps visualize that scenario, as the suction side isn't technically sucking.

    Sent from my MZ601 using Tapatalk
    Guinness for strength

  9. #9
    Join Date
    Jun 2004
    Location
    Olean, NY
    Posts
    1,449
    Scratch that, not what I meant to say and now I can't delete it

    Sent from my MZ601 using Tapatalk
    Guinness for strength

  10. #10
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,596
    Here's something that might help. Indoor wet bulb and outdoor ambient are the driving factors in deriving a target superheat, which may in a way help you understand what you're asking about. Remember that IDWB will tell you the load on your evaporator. The greater the differential, the more flow.
    If the ambient is 60 and head pressure is low, your differential between condenser and evaporator is very low.

    Does that make any sense?

    Here's the formula if you want to try to play with some numbers:

    Target superheat formula
    (indoor wet bulbx3-80- ambient temp)/2

    64 wb
    91 amb
    64x3-80-91 divided by 2
    10.5 target

  11. #11
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,042
    thank you ryan that does help

  12. #12
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    4,036
    As everyone else has said. On a cooler day your pressures will be lower. This means refrigerant flows thru MD slower which can pick up more heat. You will most likely have a higher superheat on a cooler day.

    I always thought the opposite. Then i found a york charging chart. It should high superheat on cooler days and low superheat on hotter days. Then it all clicked.

  13. #13
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,596
    Make sure you report back how the teacher reacts when you tell him he's wrong and prove it....

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