Results 1 to 4 of 4

Thread: Hermetic compressor vs. Semi Hermetic compressor

  1. #1
    Join Date
    Apr 2011
    Minneapolis, MN

    Hermetic compressor vs. Semi Hermetic compressor

    This is another free tip from JCY.

    JCY has been getting a lot of inquires/questions regarding a better style compressor in there chiller.

    Here is an example of the differences between hermetic and semi hermetic compressors-

    Hermetic compressors are completely sealed housing, with its motor also sealed in same housing. It is leak proof but cannot be repaired.
    JCY has personally seen them to only last between 2-3 years (very rare but sometimes 3+ years depending on application). These style compressors just don’t seem to hold up that well compared to semi hermetic compressors. These style compressors are classified in the refrigeration field as “throw away/cheap compressors”. There best application is for Air-conditioning.

    Semi-Hermetic compressors are also housed with motor in the same housing but the casing is bolted type and can be repaired easily.
    JCY has personally seen them to last between 3-10 years (rare but sometimes 10+ years depending on application). These styles of compressors are built for longevity, repairable and more reliable.

    JCY uses semi-hermetic compressor 19 out of 20 times, in all of our units.

    The life of a compressor is biased on its application, time it has been running, glycol used and so many other factors.

    In the refrigeration world, you can see compressors lasting either a short period of time or long.

    “These statements above are what JC Younger Company’s has personally seen since the 1970’s.”

    Cheerz and thankz Sandy Y.
    Brewery Department Manager.
    Last edited by JC Younger; 05-30-2012 at 11:25 AM.
    J.C. Younger Company
    (952) 929-1838

  2. #2
    Join Date
    May 2011
    Chicago, IL
    I'm not a HVAC person but I do have an air cooled chiller (water not glycol) for my plastics processing company. In talking with the servicemen over the years, they seem to think that hermetically sealed is better when placed in a proper designed unit. The reason being is that there's less chance of freon leaking out since the moving parts of the compressor are contained within the refrigeration system. The "properly designed" statement that I mentioned is in reference to how the compressor is used, in particular, how it cycles on and off. Compressor wear and tear stems from the cycling on and off to cool and stop cooling. In my chiller, instead of the compressor only being able to cycle on and off to control temperature it is equipped with a 'hot gas bypass' valve. This valve helps overcome the need for the constant on/off cycling of the compressor. Yes, it is wear and tear item (the bypass valve) but it's cheaper to replace that then the compressor. My valve typically lasts 4-5 years before it starts to stick in either open/closed position and the chiller is no longer cooling efficiently. I don't think I've seen glycol chillers with this bypass vale feature. Again, this is what I've learned over the years from the servicemen who work on my chiller. By the way, my chiller was made in 1984 and it still has the original Copeland compressor.

  3. #3
    Join Date
    Jul 2005
    Auburn, WA / Winston Salem, NC
    Although the hermetic compressors are not serviceable and thus less expensive to produce, I think Bmason hit the nail on the head and agree that the key is having the proper compressor that is designed for the duty and application, whether it is a hermetic or semi-hermetic.

    We've found a mix of using both styles, with the hermetics on systems in the 2-10 HP range and semi-hermetic on systems 10 HP and larger. I would guess the breakdown is 30% hermetic and 70% semi-hermetic.

    We have 20 year old systems operating with the original compressors (both hermetic and semi-hermetic)- a well designed system with proper safeties and controls is definitely the key- coupled with good preventive maintenance. Brewery chiller systems operate 24/7/365, some care and feeding is required.

    As anyone in the refrigeration business knows, there are lots of causes for compressor failures- I wouldn't accept the excuse that a compressor failed simply because is was hermetic. If someone loses a compressor, of any style, after just 2-3 years, there is likely something that is causing it.

    Good luck,


    Pro Refrigeration Inc.

  4. #4
    Join Date
    Jul 2014
    antananarivo madagascar

    hermetic compressor

    I came accross this website to read more info on hermetic compressor:

Posting Permissions

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