Eric Mele gives us an overview of a parallel rack refrigeration system. He shows and describes the components of a grocery rack.

Parallel rack refrigeration systems have multiple compressors that are all tied together in parallel. So, the discharge and suction are all tied in together. Each compressor’s discharge line will drop down into one main discharge line. That main discharge line has an oil separator, which returns the oil to the reservoir and allows the refrigerant to proceed to the condenser outside the rack room.

The refrigerant liquefies in the condenser and comes out via the liquid line. Refrigerant in the liquid line goes to the receiver, which is located underneath the compressors in this system but can be remote as well. The refrigerant then goes through the liquid line drier and to the remote liquid header. The liquid goes down to all of the cases and loads beneath the rack room, which are often walk-in refrigerators (where the heat absorption happens).

Behind the liquid header, we have suction lines with EPR valves. These EPR valves are electronic, which regulate the suction gas to achieve 100% runtime between defrosts. The suction lines all tie together into a common suction header, which then ties into the suction side on each compressor.

The oil separator and reservoir are critical components of rack refrigeration systems. The oil reservoir must be able to supply oil across three (or more) compressors.

Overall, the goals of a rack refrigeration system are to keep compressors running as long as possible, share the refrigerant charge, share the load, and try to achieve 100% runtime between defrosts.

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36 thoughts on “Rack Refrigeration 101 Definition and Overview

  1. tannerharkey says:

    Perfect timing if I do say so myself, my employers are manufacturing chiller skids for Walmart coolers and they pipe in to Walmart’s existing rack system. Our skid contains a braze plate, special set of pumps, a set of eev’s, glycol feeder tank, and new set of controls. Trying to find more information about rack systems.

  2. Mugilan T says:

    Master One question :
    This is "parallel rack system", i.e common header for all Evaporator suction line and common reciever for all compressor.

    What is "series rack system" ?
    My idea : If there realy exist "series rack system", then it will be two or multi stage compression system.

  3. Dave Hogan says:

    Thank you, been doing refrigeration for 27 years.
    Never had the opportunity to work on those system….in fact must admit I’m a little intimidated of them, leaks must be a nightmare to deal with.
    Looking forward to the other vids you’ll be posting on these systems

  4. IAmBen says:

    I work around these every once in awhile. I'm a supermarket refrigeration tech and some of the stores we've got have parallel racks. A lot better than singles! Unless the charge blows lol.

  5. HVACR Northeastern says:

    I did racks about 7 years when l start my career l was lucky that l had a good knowledge of reading schematics and good electric background .Troubleshoot is 75% is electric and 25% mechanical of troubleshooting plus you have the BAS and rack controls . You only enough time due food spoil $$$ 4 hours was maximum from the time you get the call .

  6. Vital Ral says:

    worked on racks all my life.
    never once I regretted.
    never worked on residential equipment and never will.
    money is good cause there aren't many techs who can work on them while
    everyone else is doing hvac.

  7. Tyrone Sheppard says:

    I see that the rack in this video is a low temperature rack based on the head fans. Also, I didn't notice any mechaical subcooler in the liquid line before the liquid is fed down to the cases. But there may be one. I just didn't notice it. Good video!

  8. TennesseeHVAC says:

    I am graduating HVAC/R school in Dec. I have a job offer doing light commercial, and refrigeration. This video helped show me the basics. I can't wait for your future videos on this subject! Any pointers would be appreciated. Thanks.

  9. David Jackson says:

    It will be a year since I started working for Walmart as a refrigeration tech and I got to say working on rack systems can be great and a pain at the same time, but I sure do enjoy it

  10. VTdarkangel says:

    Someone has spent the time keeping this rack up. I can tell by some of the controls, this is an older rack. The insulation has been clearly replaced (and very well done at that) and it looks like some of the other controls have been updated.

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