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Thread: Superheat

  1. #1
    Join Date
    Jul 2006
    Location
    Little Rock AFB
    Posts
    10
    I understand the comments, I have been doing HVAC for 13 years in the south, Fl, Ga, Ar, somehow I didn't master superheat and I'm trying to get my head around it a little better, thanks for any help

  2. #2
    Join Date
    Jul 2006
    Location
    Lancaster,Ohio
    Posts
    464
    I know some techs that have no clue what superheat or subcooling is. One is actualy a very impressive tech. Freddie, Before you worry youself trying to learn how to use superheat, learn completly what it is. Once you know what it is, it all becomes simple.
    IcyFlame

  3. #3
    Join Date
    Jul 2006
    Location
    Little Rock AFB
    Posts
    10
    I'm trying I printed some stuff out last night and have been reading it, I'm actually a good honest tech and usually get called when other guys hit a wall, but this has always bothered me and I wanted to get it figured out.

  4. #4
    Join Date
    Sep 2002
    Location
    I don't know
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    2,909
    Required reading:

    http://hvac-talk.com/vbb/showthread.php?threadid=54493

    http://www.hvacloads.com/talkpdf/tro..._superheat.pdf

    http://hvac-talk.com/vbb/showthread.php?threadid=33829

    Also get your hands on a pressure-saturation temperature chart + a fixed orfice charging chart.

  5. #5

    Talking Super Heat

    Super Heat is a real hot day in Southern California, right?

    13 years in the buisness and still putting them filters in upside down are we?

    Comon who needs to nkow about Super Heat anyway, these things come right out of the box fully charged...
    AllTemp Heating & Cooling

  6. #6
    Join Date
    Jun 2004
    Posts
    459

    defining superheat

    freddie, let's define what super heat is. once we thourouly understand the definition, then we can work with it.

    superheat = the number of degrees by which the unsaturated vapor (containing no liquid) exceeds the temperature of a saturated vapor (containing liquid) at the same pressure.

    trying to keep it simple, as the refrigerant travels through the evaporator, it is in a saturated vapor state (liquid/vapor state). as the refrigerant absorbs heat, it flashes into a vapor eventually there is no liquid refrigerant left. this is all happening at the same pressure. as the refrigerant continues its journey through the evaporator as 100% vapor (unsaturated) it gains additional heat (temperature rises) this temperature increase of unsaturated temp above saturated temp is your superheat

    like to add a note on this, when you read your gauges, you are reading saturated pressures (liquid/vapor state)

  7. #7
    Join Date
    Jul 2006
    Location
    NJ
    Posts
    356

    Super heat / hope this helps

    Super heat must be calculated! its is defined as the tempiture of the refrigerant leaving the evaporator above its saturation. Example: at 62 pounds on the suction line
    our saturation for R22 is approx 33 degrees, if we measure the tempiture of the suction line and it reads 45 degrees than our superheat reading is 45 - 33 = 12 degrees superheat, However, this is only called a super heat reading! The actual superheat load of a home will change with two tempitures "the indoor wetbulb and the out door temp" Get a superheat calculator from your dealer. to calculate what the superheat should be for that day take a indoor wet bulb reading and an outdoor temp.
    Example: indoor wetbulb is 62 outdoor temp is 85, the super heat chart tells us the superheat should be 8 degrees. our gauges read 62 pounds on the suction,if we convert that 62 pounds to saturation it is 33 degrees, so we take a temp reading off the suction line and it should be 8 degrrees higher than the 33 saturation (+-3)temp reading should be 41 degrees.
    Example 2: indoor wetbulb is 74 outdoor temp is 85, the super heat chart tells us the superheat should be 30 degrees. our gauges read 62 pounds on the suction,if we convert that 62 pounds to saturation it is 33 degrees, so we take a temp reading off the suction line and it should be 30 degrrees higher than the 33 saturation (+-3)temp reading should be 63 degrees.

    YOU MUST BE CAPABLE OF OBTAINING A WET BULB READING TO CALCULATE YOUR SUPERHEAT. YOU WILL FIND MOST ALWAYS THAT THE THE ONLY THING YOU NEED GAUGES FOR IS TO CONVERT YOUR PRESSURE TO SATURATION.

    so check suction pressure and convert it to saturation/ then take the actual suction line temp,

    [Edited by bonafide on 07-28-2006 at 07:19 PM]

  8. #8
    It also requiars a DB temp and the other readings you mentioned to claculate a satisfactory set point.
    And please Make sure you have a Clean filter!!

  9. #9
    Join Date
    Jul 2006
    Location
    Lancaster,Ohio
    Posts
    464
    Bonifide, you articulated superheat very nicely. No dealers around me can get the superheat calculater. They make me feel lucky to get a ductulator. Do you have an extra?
    IcyFlame

  10. #10
    Join Date
    Apr 2004
    Location
    Meridian, MS
    Posts
    268

  11. #11
    Join Date
    Mar 2004
    Location
    Illinois
    Posts
    6,959
    Since you're in the HVAC/R field, please sign up as a Professional Member so that we can move this to the Pro-Forum for further discussion.

    Thank You

  12. #12
    Join Date
    Jul 2006
    Location
    NJ
    Posts
    356

    Thumbs up

    If your dealer does not have,
    The best thing to do is go online and copy paste and laminate the charts. I always have at least five on truck in case one gets lost.
    hear is a good link that also has some helpful subcooling info.







    http://www.refrig.com/charge.html

  13. #13
    Join Date
    Nov 2004
    Location
    NJ
    Posts
    1,205
    I’ve found that techs that don’t understand superheat or subcooling lack a true understanding of the basic refrigeration cycle; this knowledge is crucial for correctly diagnosing air conditioning systems.

    It’s scary to think there are “techs” out there who don’t understand this basic theory. Kinda like an auto mechanic working on your car who doesn’t understand the theory behind the internal combustion engine.

    Good for you Freddie for wanting to learn this, it will make trouble shooting systems so much easier .
    Ed J

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