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  • Chiller compressor the right kind?

    Hey guys, I'm afraid we got ripped off on our glycol chiller.

    We've got a 8 hp Copeland scroll compressor (ZR94KC-TF5-450), a reserve tank that's got a capacity of around 1000 liters, plus around 218 liters of cooling liquid in the tubing.

    The glycol unit was assembled by a guy who I found out (after the purchase) has a bad reputation and I am looking for a sanity check that this is the right type of compressor to do the job. I understand that the unit's horsepower is good enough for my thermal load of 50,000 BTUs, my concern and question is this the right type of compressor. Another refrigeration guy told me that this compressor is hermetic and that a semi-hermetic would do the job much more efficiently.

    The system frequently feels like it's fighting to keep the temps down.

    What kind of trade offs am I looking at in what I have vs a semi-hermetic unit?

  • #2
    Check out this older post. I think it answers your question.

    Comment


    • #3
      Originally posted by ericksonaz View Post
      Check out this older post. I think it answers your question.

      http://discussions.probrewer.com/sho...tic-compressor
      Thanks! Should have searched haha

      Comment


      • #4
        That was then, this is now.

        That post is from 2012.

        We lost a semi-hermetic comp on our old Pro system about 4 years ago, around the time that post was written. The windings on the motor had died. Pro replaced the comp, explaining that, while it could be repaired in theory, practically it was a better deal to replace the entire comp. So much for repairability.

        About 3 years ago, we purchased a new two stage, 7.5hp X 7.5hp chiller from Pro. Both the comps are hermetic. We were told that the difference in durability was more than made up for by the difference in cost. 3 years and both are still going strong, with the ancient semi-hermetic serving back-up duty.

        As another practical point, the hermetics are much quieter than the semis.
        Timm Turrentine

        Brewerywright,
        Terminal Gravity Brewing,
        Enterprise. Oregon.

        Comment


        • #5
          Originally posted by TGTimm View Post
          That post is from 2012.

          We lost a semi-hermetic comp on our old Pro system about 4 years ago, around the time that post was written. The windings on the motor had died. Pro replaced the comp, explaining that, while it could be repaired in theory, practically it was a better deal to replace the entire comp. So much for repairability.

          About 3 years ago, we purchased a new two stage, 7.5hp X 7.5hp chiller from Pro. Both the comps are hermetic. We were told that the difference in durability was more than made up for by the difference in cost. 3 years and both are still going strong, with the ancient semi-hermetic serving back-up duty.

          As another practical point, the hermetics are much quieter than the semis.
          Thanks for your perspective Timm. That's good information to have that the repairability factor didn't do anything for you guys.

          Comment


          • #6
            and if im stating the obvious forgive me, but you want a medium temp compressor unit. high temp units are for air conditioning type uses and are typically rated for 45ish to 60ish temps. (might be bit off there).

            using a high temp unit will wear the hell out of it at medium (+/-28F) temps and de-rates the hell out of the btus as well.

            Comment


            • #7
              Originally posted by brain medicine View Post
              and if im stating the obvious forgive me, but you want a medium temp compressor unit. high temp units are for air conditioning type uses and are typically rated for 45ish to 60ish temps. (might be bit off there).

              using a high temp unit will wear the hell out of it at medium (+/-28F) temps and de-rates the hell out of the btus as well.
              Sorry, the unit that we have is for air conditioning?

              This reinforces my decision to sue the guy who built the system.

              Comment


              • #8
                I'm not finding much on that model of comp--it looks like it may be discontinued.

                It does appear to be an air conditioning comp, and it looks like it's designed for R22. R22 barely exists these days.
                Timm Turrentine

                Brewerywright,
                Terminal Gravity Brewing,
                Enterprise. Oregon.

                Comment


                • #9
                  There definitely could be some issues with your chiller, but I wouldn't call your attorney yet...

                  First things to look at:

                  1. Is it making cold? If you set it to 30F (or whatever) does it get to 30F? This is very important. As a chiller MFG, we deal with this all the time "my XYZ isn't getting cold." If the water or water/glycol is getting to the setpoint and the compressor(s) are cycling off and unloading, but the XYZ is still warmer than desired, then the issue is one of heat transfer between the glycol and XYZ. This could still be chiller related in terms of the pump flow rate, but not necessarily a refrigeration capacity issue.

                  2. Are you having any kinds of faults, trips, alarms? Voltage issues?

                  3. What refrigerant are you using? TGTimm is correct that that part # that is an R-22 compressor. Current models are very similar; ZR94KCE would be identical in capacity but has the ability to use different refrigerants.

                  If you look at item 1 above, and you are not making setpoint, then it could be a chiller capacity issue. Does the chiller make setpoint sometimes, but not others? Can you correlate the times it is not making temp to specific process in the brewery (number of tanks being crash cooled, secondary heat exchange, time of day) ?

                  Air Conditioning vs. Refrigeration Compressors

                  The blanket statement that an A/C compressor can only be used for air conditioning and cannot be used for a brewery chiller is incorrect. All compressors have what is called an operating envelope. If is a graph showing a rectangular-ish shape. THe X-axis is the suction temperature, the y-axis is the condensing temperature. Condensing temperature is proportional to ambient temperature, and suction temperature is proportional to the chilled water temp. The conditions under which the compressor operates must fall inside the shaped drawn on the operating envelope. At generally accepted “brewery chiller” conditions, both AC and Refrigeration compressors have operating envelopes that surround “standard” brewery conditions. The reality is, as far as “refrigeration” goes, brewery chiller really don’t run that cold.
                  The conditions in which a refrigeration compressor will work and an AC compressor will not (and vice versa) are at the extremes of the performance which are rarely encountered in a correctly designed brewery chiller. OF COURSE there are exceptions to this.

                  Efficiency
                  Comparing your compressor to a Bitzer 404 scroll, a Copeland 404a scroll, and to a Bitzer R-404a semi-hermetic at the same operating conditions yielded the following results: (Based on EER, higher the number the greater the efficiency in terms of BTU/HR per kW of consumption).
                  R-22 Scroll- EER 8.28 (A/C)
                  R-404a Scroll Copeland- 6.89 (Refrigeration)
                  R-404a Scroll Bitzer- 7.39 (Refrigeration)
                  R-404a Recip Bitzer-8.23 (Refrigeration)

                  Operating Envelope

                  This is kind hard to explain without pictures, but the “most inside” the operating envelope was the R-404a Semi-hermetic. They are a little more ruggedly built and can handle slightly higher compressor ratios than the scrolls. Second Place was the Copeland R-404a scroll, 3rd place is the Copeland R-22 scroll, 4th place was the Bitzer R-404a Scroll.
                  As an interesting aside, an R410a scroll, and a sem-hermetic with R-134a (both considered A/C refrigerants) had operating envelopes on par to slightly higher than all four of the other compressors listed. The efficiencies at the same conditions were 2% (R10a scroll) and 10% (134a recip) than the most efficient compressor on the prior list.
                  So what all this info is saying is that I think you should take a look deeper at what is going on. Based on the info provided, popping in a different type of compressor of the same capacity, but of a different type or different refrigerant will probably not fix your problem. You certainly may have some issues with your chiller, but there a lot of other things I would look at first.

                  As a side note we use primarily Bitzer compressors. Primarily 410a scroll, proceeded by Bitzer 404a recips and then R-404a scrolls (very rarely). Didn't want to sound like I was bashing Bitzer.

                  I hope this is helpful.

                  Jeff Johnson
                  Johnson Thermal System
                  Johnson Thermal Systems
                  sales@johnsonthermal.com
                  Johnsonthermal.com
                  208.453.1000

                  Comment


                  • #10
                    Thanks so much for the writeup, Jeff. I'll take all of this into consideration. We have, in fact, had issues getting and maintaining set point. But, they could be solved by redoing the insulation on the tank. The constructor put a half inch of glued foam bullshit around the sides and left the bottom totally exposed.

                    Would you say that it's okay to run this particular compressor at below freezing? I can get the tank down to -4 C, but not when it's recirculating. It struggles to maintain 2 C with recirculation going (with all the tank solenoids closed). After properly insulating the tank, I'd really like to run it at negative temps so I can properly brite.

                    Comment


                    • #11
                      This compressor is able to handle below freezing temps.

                      A compressor doesn't "see" the chilled water temp. It just sees the suction temp of the refrigerant. This is the temperature of the refrigerant that actual cools the glycol. Since heat flows from hot to cold, this temperature is ALWAYS lower than the chilled water temp. With a properly selected evaporator, this temperature should be 4-6C lower than the chilled water temp.

                      At the same time, the condensing temperature is what the compressor "sees" on its discharge. This is ALWAYS higher than the temperature of the air entering your condenser. This is usually 11-16C higher than the air temperature. Assuming your suction and condensing temperatures are in this range, you should not have a problem running your setting point to -4C. If it is really hot where you are or you don't have good condenser air flow, I would keep it around -2C.

                      These are all just ranges of what could be considered normal. If the chiller is design poorly or the there are some kind of other issues (dirty condenser, fouled evaporator) you could run the compressor outside of it's envelope.

                      Running I these conditions not only have the room of running g outside the operating envelope, these reduce the capacity of the system.

                      You said the chiller could make -4C without recirculation. What does this mean? Does this mean you are running a two pump system, and recirculation means the pump that distributes glycol to the brewery is running?

                      Also, I don't understand when you say with recirculation but also "all solenoid valve are closed." If they are all closed then that would mean you are not picking up any load from the system.

                      From your description, the way I am visualizing the situation is that when the chiller just runs with no load, you can get to -4C. Pump when you turn on your circuit pump and pick up load from the brewery, you can't keep up. If I am understanding this correctly, this would mean that the chiller capacity is lower than the heat load.

                      This could mean the chiller is too small, or there are operation or design issues that reducing it's capacity.

                      For what it's worth, the ZR9KC compressor capacity is approx 60,000 btu/hr with 20F suction temp and 120F condensing temp.

                      If you could clarify your pump situation I might be able to help more.

                      Jeff

                      Sent from my XT1650 using Tapatalk
                      Johnson Thermal Systems
                      sales@johnsonthermal.com
                      Johnsonthermal.com
                      208.453.1000

                      Comment

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