Page 1 of 4 1234 LastLast
Results 1 to 13 of 40
  1. #1
    Join Date
    Jul 2005
    Posts
    9

    Hmm

    what is the best way to check superheat on any equipment

  2. #2
    Join Date
    Feb 2005
    Location
    Central Alabama
    Posts
    466
    Take low side pressure and p/t chart .convert low side press. to temp. then take line temp of suction line near condensing unit and subtract the two and the diff. is superheat.

  3. #3
    Join Date
    Apr 2004
    Posts
    395
    P/T Chart,Good set of gagues Thermometer and a Fluke Line Clamp
    Tin Knockers BANG for a living

  4. #4
    Join Date
    Apr 2005
    Location
    where the beer flows like wine
    Posts
    2,871
    Originally posted by bama 101
    Take low side pressure and p/t chart .convert low side press. to temp. then take line temp of suction line near condensing unit and subtract the two and the diff. is superheat.
    I never hear of taking condensing temp for superheat. or a suction line near condensing unit. you may want to re-check your post!

  5. #5
    Join Date
    Feb 2005
    Location
    Central Alabama
    Posts
    466
    hvac pope care to give more info ? I was tought to take saturation temp of evap and suction lin temp 8 in from compressor and or suction line on outside of condenser please correct me if i'm wrong

  6. #6
    Join Date
    Feb 2005
    Location
    Central Alabama
    Posts
    466
    Evaporator Superheat
    Check Your Superheat. After the box temperature has reached
    or is close to reaching the desired temperature, the evaporator
    superheat should be checked and adjustments made if necessary.
    Generally, systems with a design TD of 10F should have a
    superheat value of 6 to 10F for maximum efficiency. For systems
    operating at higher TDʼs, the superheat can be adjusted to 12 to
    15 F as required.
    NOTE: Minimum compressor suction superheat
    of 20F may override these recommendations
    on some systems with short line runs.
    To properly determine the superheat of the evaporator, the following
    procedure is the method Heatcraft recommends:
    WARNING: If the condensing unit has no flooded
    condenser head pressure control, the
    condensing unit must have the discharge
    pressure above the equivalent
    105F condensing pressure. See refrigerant
    charging instructions on page 30.
    1. Measure the temperature of the suction line at the point
    the bulb is clamped.
    2. Obtain the suction pressure that exists in the suction line
    at the bulb location by either of the following methods:
    a. A gauge in the external equalized line will indicate the
    pressure directly and accurately.
    b. A gauge directly in the suction line near the
    evaporator or directly in the suction header of the
    evaporator will yield the same reading as 2a above.
    3. Convert the pressure obtained in 2a or 2b above to
    saturated evaporator temperature by using a
    temperature-pressure chart.
    4. Subtract the saturated temperature from the actual
    suction line temperature. The difference is Superheat.
    Alternative Superheat Method
    The most accurate method of measuring superheat is found by
    following the previous procedure, Temperature/Pressure method.
    However, that method may not always be practical. An alternative
    method which will yield fairly accurate results is the temperature
    / temperature method:
    1. Measure the temperature of the suction line at the
    point the bulb is clamped (outlet).
    2. Measure the temperature of one of the distributor
    tubes close to the evaporator coil (inlet).
    3. Subtract the inlet temperature from the outlet
    temperature. The difference is Superheat.
    This method will yield fairly accurate results as long as the pressure
    drop through the evaporator coil is low.

  7. #7
    Join Date
    May 2004
    Posts
    12,028

  8. #8
    Join Date
    Oct 2007
    Location
    Plainfield Il
    Posts
    43
    The super heat can be measeure leaving the evaporator or at the compressor. You want to take you pressure reading at the suction line on the evaporator, convert oressure to saturation temp. Measure suction line with clampo on meter just out side of the evaporator case. Make sure box is at temp other wise false readings. Suptract the saturation temp from the line temp and that is your evap superheat.

  9. #9
    Join Date
    Oct 2008
    Posts
    171
    Good link Lusker!

    This one is my fav.

    http://www.hvaccomputer.com/hvac/sizer.asp

    roflmao!



    Quote Originally Posted by Lusker View Post
    Old, Bald and Cranky

  10. #10

    superheat

    Quote Originally Posted by adammemin View Post
    The super heat can be measeure leaving the evaporator or at the compressor. You want to take you pressure reading at the suction line on the evaporator, convert oressure to saturation temp. Measure suction line with clampo on meter just out side of the evaporator case. Make sure box is at temp other wise false readings. Suptract the saturation temp from the line temp and that is your evap superheat.

    The temp.taken by the compressor can be a few degrees higher,so the best way is to be taken by the evap.

  11. #11
    Join Date
    Sep 2008
    Location
    Cedar Rapids, IA
    Posts
    486
    Quote Originally Posted by hvacpope View Post
    I never hear of taking condensing temp for superheat. or a suction line near condensing unit. you may want to re-check your post!
    You can't be sure your superheat readings will be correct unless the liquid to the TXV is adequately subcooled to prevent flashing. What is adequate depends on liquid line lengths/sizes and relative elevation of the condenser and evaporator.

    There are two places to measure superheat and BOTH should be checked. The first is at the evaporator suction line. The second is at the compressor suction line. All hermetic and semi-hermetic compressors have minimum and maximum superheat requirements and some have desuperheat injectors and hot gas bypass that further complicates the issue.

  12. #12
    Join Date
    May 2007
    Location
    Alabama
    Posts
    909
    Quote Originally Posted by jdaug1 View Post
    Good link Lusker!

    This one is my fav.

    http://www.hvaccomputer.com/hvac/sizer.asp

    roflmao!
    That's the one I use! By far the easiest sizing calculator. I swear by it, and anyone can use it!

  13. #13
    Join Date
    Oct 2007
    Location
    Plainfield Il
    Posts
    43
    Quote Originally Posted by MRcoolingMAGIC- View Post
    The temp.taken by the compressor can be a few degrees higher,so the best way is to be taken by the evap.
    The temp taken at the compressor will be more than a few degrees higher. A tipical walk-in cooler set up with a copeland recip. requires 6-8 deg of super heat at the evap and 20 deg of superheat at the compressor. Now there are a lot of factors to take in consideration. How well is the suction line insulated??? Should have at least 1/2 armaflex on a cooler and 3/4 on a freezer. How long is the line set???? Now there are a lot of units that the suction line insulation has worn off from the elements and if you check the superheat at the evap it may be correct, but the superheat at the compressor will be high. The compressor needs that liquid to keep it cool.

Page 1 of 4 1234 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event