Results 1 to 16 of 16
  1. #1
    Join Date
    Mar 2016
    Location
    Saudi Arabia
    Age
    26
    Posts
    6
    Rep Power
    0

    Lightbulb Some technical questions



    Hi i have some questions related to refrigeration and compressor . i work in a company and we have sabroe 128HM compressors for cold storage.

    1: whats the difference between suction temperature and suction super heat, also discharge temp and super heat.

    2: there is one room which give problems , set temp is 4'C while room temp stay above 6'C. there's anothor temp mention in the PLC display "duct temp" we don't have ducts. we have liquid R22 line. what's a duct temp? duct temp always stay in between 4 and 6 degree C. Is this the temp of small duct after the expansion valve which has further parallel branches in the evaporator ?

    3: Does anyone has worked with the sabroe 128HM mkIII , i have problem understanding the functions of some pipe connections to the compressor.



  2. #2
    Join Date
    Feb 2007
    Location
    UK
    Posts
    2,479
    Rep Power
    38

    Re: Some technical questions

    Hi Fakhr,

    1. Suction temperature is the actual measured temperature of the refrigerant returning to the compressor,
    Super heat (or, in case of refrigerant in liquid state, sub cooling) is the difference between the saturated temperature of the refrigerant at a given pressure and the actual measured temperature.

    2. The duct temp is most likely the temperature of the air exiting the evaporator and being supplied it to the room.


  3. #3
    Join Date
    Mar 2016
    Location
    Saudi Arabia
    Age
    26
    Posts
    6
    Rep Power
    0

    Re: Some technical questions

    Quote Originally Posted by The Viking View Post
    Hi Fakhr,

    1. Suction temperature is the actual measured temperature of the refrigerant returning to the compressor,
    Super heat (or, in case of refrigerant in liquid state, sub cooling) is the difference between the saturated temperature of the refrigerant at a given pressure and the actual measured temperature.

    2. The duct temp is most likely the temperature of the air exiting the evaporator and being supplied it to the room.

    ok . but i don't get the readings on compressors electronic display. its showing suc tem and superheat at the same time . see it for yourself.

    S60403-145455.jpgS60403-145500.jpg

  4. #4
    Brian_UK's Avatar
    Brian_UK is online now Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
    Join Date
    Mar 2001
    Location
    Dorset
    Age
    69
    Posts
    10,372
    Rep Power
    49

    Re: Some technical questions

    Quote Originally Posted by Fakhr E Alam View Post
    ok . but i don't get the readings on compressors electronic display. its showing suc tem and superheat at the same time . see it for yourself.

    S60403-145455.jpgS60403-145500.jpg
    Yes, that is correct, the two temperatures are distinct and separate. The Viking explained them above. M
    Brian - Newton Abbot, Devon, UK
    Retired March 2015
    Please support http://the100project.net/Home

  5. #5
    Join Date
    Mar 2016
    Location
    Malaysia
    Posts
    8
    Rep Power
    0

    Re: Some technical questions

    So the 27,5 is the suction temperature and the 58 is the discharge temperature leaving the compressor
    Last edited by Lundh; 03-04-2016 at 03:01 PM. Reason: wrong

  6. #6
    Join Date
    Mar 2016
    Location
    Malaysia
    Posts
    8
    Rep Power
    0

    Re: Some technical questions

    Regarding the cold room temperature issue. Does the compressor runs continually? I think you should check a number of things to troubleshoot why the cooling is insufficient:

    Suction pressure
    Thermostat
    If the compressor runs continually
    Filter
    Blocked condenser --> condensing pressure
    Shortage of refrigerant

  7. #7
    Join Date
    Jan 2006
    Location
    Croatia
    Age
    62
    Posts
    2,116
    Rep Power
    23

    Re: Some technical questions

    Hi, Fakhr E Alam

    Quote Originally Posted by Fakhr E Alam View Post
    ok . but i don't get the readings on compressors electronic display. its showing suc tem and superheat at the same time . see it for yourself.

    S60403-145455.jpgS60403-145500.jpg
    Your suction pressure of 1,9 bar corespond to saturated temperature of ST -15,6*C (257,55K) from tables for R22 ... for other refrigerants is different ... UNISAB II can be set up in that way too .. to read *C/R or *F/R or bar/psi ... you need to read your Unisab manual how to set up start screen and which units you want to use .. pressure or temperature

    you can download app for your computer or for your phone ... just google for ... refrigerant slider ... or click on link ... to se tables for refrigerants ...

    http://refrigerationandairconditioni...ware/coolapps/

    https://play.google.com/store/apps/d...anfoss.koolapp

    http://windowsphoneapk.com/APK_KoolA...ows-Phone.html


    .... your actual suction temperature is 8,8*C (281,95K) ... ((8,8 - (-15,6))= 8,8+15,6 = 24,4 *C,
    but the right way is to say 24,4K without "degree" just Kelvin ... (281,95 - 257,55) = 24,4K

    the difference between suction saturated temperature and actual temperature we call suction superheat (SSH), but should be expressed in K ... thus, always positive value even if we are completely in negative temperature expressed in *C ...

    for exmaple ST=-42,5*C (230,65K) and actual temperature at compressor suction is -21,8*C (251,35K) we cannot say that SSH is ... (minus) -20,7*C ... can be only 20,7*C or simply 20,7K ... there is no negative SSH ...(SuctionSuperHeat)
    all is much easier when we use absolute temperature scale .... because there is no negative temperature expressed in absolute scale i.e. K (Kelvin) ... the lowest temperature in the universum is 0K ...

    ... your actual discharge pressure is 11,3 bar and correspond (again to saturated temperature from tables) to 31,4*C (304,55K) and your actual discharge temperature is 58,3 *C (331,45K) .... the difference between discharge actual temperature and saturated temperature we call discharge superheat (DSH) and should be expressed in K too .... i.e. (331,45 - 304,55) = 26,9K

    For problems regarding function/s of compressor piping .... please .... upload a scheme of your compressor (can be hand made drawing) and mark pipes which function you do not understand ...


    Hope this will be of some help to you.

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  8. #8
    Join Date
    Mar 2016
    Location
    Malaysia
    Posts
    8
    Rep Power
    0

    Re: Some technical questions

    Hi Joseph,

    That was a very good explanation,you made it very clear how to read and understand the data
    So there is nothing wrong with he's suction and discharge pressure. Do you have any qualified advisces for what he should check to figure out the problem? I think troubleshooting in refrigerant systems is very interesting

  9. #9
    Join Date
    Jan 2006
    Location
    Croatia
    Age
    62
    Posts
    2,116
    Rep Power
    23

    Re: Some technical questions

    Hi, dear Lundg

    Quote Originally Posted by Lundh View Post
    Hi Joseph,

    That was a very good explanation,you made it very clear how to read and understand the data
    So there is nothing wrong with he's suction and discharge pressure. Do you have any qualified advisces for what he should check to figure out the problem? I think troubleshooting in refrigerant systems is very interesting
    thanks ....

    ... probably there is nothing wrong with both pressures - if system required to be set in that way (that we do not know - together with some other important data) but for sure suction superheat (SSH) is too big ... but ... again big ... BUT....

    .... if the temperature within cold room must be 4*C (277,15K) and suction pressure/temperature is at -15,6*C (257,55K) ... something is not good

    ... to run a cold room at 4*C ... suction temperature can be at -5*C or even at 0*C (268,15K - 273,15K) ... there can be a lot of causes to have that discrepancy ...

    OP wrote:
    Quote Originally Posted by Fakhr E Alam View Post
    2:there is one room which give problems , set temp is 4'C while room temp stay above 6'C. there's anothor temp mention in the PLC display "duct temp" we don't have ducts. we have liquid R22 line. what's a duct temp? duct temp always stay in between 4 and 6 degree C. Is this the temp of small duct after the expansion valve which has further parallel branches in the evaporator ?

    Probably ... HE in that cold room is starving or without heat echange, because, it is blocked by ice due to too low suction temperature ... or not enough refrigerant - again low evaporation temperature .... maybe blocked filter on the liquid line to HE - because another rooms are working OK -what we do not know !?! ... but if true that means system is not empty ... maybe some valves are closed ... maybe HE is blocked with oil .... we miss a lot of data needed to give some good suggestion ... all this above is guessing and sometimes lead in wrong direction .... we are waiting for OP to give us more relevant data ... if


    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  10. #10
    Join Date
    Mar 2016
    Location
    Malaysia
    Posts
    8
    Rep Power
    0

    Re: Some technical questions

    Dear Josip,
    Yes i can see the issue with the very low suction pressure and temperature, and the SSH in this running condition is (24,7-(-15,6)) = 40,3 K which sounds crazy. The system must be running at a very low COP atm. Could this very high SSH be caused by poor or non isolated suction line? But yes alot of data is needed, i hope our Saudi friend will provide us with more useful information

    By the way do you work with installation/service and troubleshooting in refrigeration systems?

  11. #11
    Join Date
    Jan 2006
    Location
    Croatia
    Age
    62
    Posts
    2,116
    Rep Power
    23

    Re: Some technical questions

    Hi, Lundh

    Quote Originally Posted by Lundh View Post
    Dear Josip,
    Yes i can see the issue with the very low suction pressure and temperature, and the SSH in this running condition is (24,7-(-15,6)) = 40,3 K which sounds crazy. The system must be running at a very low COP atm. Could this very high SSH be caused by poor or non isolated suction line? But yes alot of data is needed, i hope our Saudi friend will provide us with more useful information

    By the way do you work with installation/service and troubleshooting in refrigeration systems?
    SSH is 24,4K ... real suction temp=281,95K - saturation temp=257,55K = 24,4K ...

    even without insulation (the other part of the system is running well), we'll get some ice formation on the suction pipe what will be quite good insulation and suction superheat will not be so big if system is working well ... compressor will run longer time and that is all ... I believe there is some other problem ....

    Yes, about 37 years ... but still learning


    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  12. #12
    Join Date
    Dec 2007
    Location
    australia
    Posts
    2,417
    Rep Power
    26

    Re: Some technical questions

    Agree with Josip,
    Also compressor suction pressure control point should be checked in Unisab, as could be set to low.
    Depends what else is on suction of this machine, rooms etc, if anything.
    From picture machine is fully loaded 100%

    Are there any back pressure regulators on 4deg C room as well?
    Last edited by RANGER1; 05-04-2016 at 10:08 PM.

  13. #13
    Join Date
    May 2016
    Location
    Philippines
    Age
    40
    Posts
    4
    Rep Power
    0

    Re: Some technical questions

    hi! can someone give an advice about suction temperature too high? and what was the cause of this alarm?

  14. #14
    Join Date
    May 2007
    Location
    Auckland
    Age
    67
    Posts
    3,362
    Rep Power
    31

    Re: Some technical questions

    High suction superheat reflects as a high discharge super heat, actual gas temperature leaving compressors versus the Saturated discharge temperature.

  15. #15
    Join Date
    May 2016
    Location
    Philippines
    Age
    40
    Posts
    4
    Rep Power
    0

    Re: Some technical questions

    We recently experienced this issue on "suction temperature too high" alarm in circuit 2 of our 40 tonners Trane CGAM Chiller. We have noticed that during standby mode the suction temp display in ckt 2 is higher by 20 degree fahrenhiet compared to ckt 1 (which is in healthy condition). After the chiller set in operation mode & both circuit are running, the suction temp of ckt 2 increases up to 160 deg.fah. while the circuit 1 remain close to entering/leaving water temp. The discharge pressure in ckt.2 is somewhat a half value of discharge pressure in ckt.1. And by the time the EXV in ckt 2 gradually increases up to 100% opening such time the ckt.2 stopped with an alarm suction temperature too high. We suspected that the problem is within the sensor, but we are not sure if this is the cause of alarm. Is there anyone can give as light regarding with our problem. thank you

  16. #16
    Join Date
    Mar 2009
    Location
    U.S.A.
    Posts
    300
    Rep Power
    12

    Re: Some technical questions

    If I read correctly: Circuit 1 is working near expectation but circuit 2 makes a low discharge pressure, does not pull down its suction pressure, and cuts out on high suction temperature after fairly short running interval.

    My first guess would be the refrigerant is short charged; and with scroll compressors, the oil in that circuit is either 1) not returning or 2) all going to one machine, the other one is more or less oil dry. Nominally, if the refrigerant has been leaking, the oil charge will be low and in the wrong place as well.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •