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  1. #14
    Join Date
    Aug 2012
    Posts
    18
    So based on the information thus far I initially charged the system on a 100 degree day with a box that was over 90 degrees. Charged to just cleared site glass. Site glass showed bubbles after 36 hours. Would those conditions cause this once the system ran awhile and box was at or close to normal operating temp? Based on the replies I am sure I undercharged the unit initially, but I am having a little diffuculty understanding the transition from full site glass (apparent full charge) to showing bubbles (apparent undercharge)

  2. #15
    Join Date
    Aug 2012
    Location
    Palmyra, Missouri, United States
    Posts
    224
    you realize that clearing the sight glass does not indicate a full charge. use subcooling with a txv.

  3. #16
    Join Date
    Feb 2009
    Location
    Wisconsin
    Posts
    311
    Unless you have a receiver. This isnt an air conditioner. Forget about subcooling.
    You have to fight through some bad days to earn the best days of your life.

  4. #17
    Join Date
    Jul 2012
    Location
    Richland, WA
    Posts
    248
    I had a similar thing happen and it turned out that there was a small leak where I didn't have the braze 100% filling the copper properly. I would double check anything that was brazed recently.

    Quote Originally Posted by tomnkc View Post
    So based on the information thus far I initially charged the system on a 100 degree day with a box that was over 90 degrees. Charged to just cleared site glass. Site glass showed bubbles after 36 hours. Would those conditions cause this once the system ran awhile and box was at or close to normal operating temp? Based on the replies I am sure I undercharged the unit initially, but I am having a little diffuculty understanding the transition from full site glass (apparent full charge) to showing bubbles (apparent undercharge)

  5. #18
    Join Date
    Aug 2012
    Location
    Palmyra, Missouri, United States
    Posts
    224
    I charge every system to 10-15 subcooling with an exspansion valve. refrigeration is refrigeration air conditioner or walk in cooler.

  6. #19
    Join Date
    Feb 2009
    Location
    Wisconsin
    Posts
    311
    Maybe I am wrong. So, 10 degree subcool would indicate approximately what level in the receiver for this freezer? 15 degree subcool what level? We are all here to learn. I am not a good teacher but I do know that there is no way to accurately charge this system with subcooling.
    You have to fight through some bad days to earn the best days of your life.

  7. #20
    Join Date
    Jul 2012
    Location
    Richland, WA
    Posts
    248
    I would also try checking the filter drier, I know most of the walkin freezers that most of the McDonalds stores I work in have filter driers before the sight glass, could very will be plugged there and flashing early.

    Quote Originally Posted by caheiman30 View Post
    I had a similar thing happen and it turned out that there was a small leak where I didn't have the braze 100% filling the copper properly. I would double check anything that was brazed recently.



    Sent from my iPhone using Tapatalk

  8. #21
    Join Date
    Aug 2012
    Location
    Palmyra, Missouri, United States
    Posts
    224
    10-15 degrees sub cooling to the txv means full charge

  9. #22
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by drife678 View Post
    10-15 degrees sub cooling to the txv means full charge
    On a hot day it may but on a 40 degree day it may be short and subcooling gone. Subcool will tell you if your overcharged on a receiver system but will only tell you there is enough charge for the ambient you have when u check it.

  10. #23
    Join Date
    Aug 2012
    Location
    Palmyra, Missouri, United States
    Posts
    224
    Quote Originally Posted by Tommy knocker View Post
    On a hot day it may but on a 40 degree day it may be short and subcooling gone. Subcool will tell you if your overcharged on a receiver system but will only tell you there is enough charge for the ambient you have when u check it.


    I always try to check subcooling right at the inlet of the exspansion valve. Wont this tell me if the charge is correct.

  11. #24
    Join Date
    May 2011
    Location
    Oklahoma
    Posts
    362
    I'm in the same situation. I was assigned a walk in cooler condenser replacement. There was no weight on the nameplate and the book just said get the low aide to 60 psi from vacuum then start it and top off from there. I am still learning refrigeration too so I just cleared the glass. It was well over 100 outside.

    Mine has an accumulator, receiver, and headmaster. Where in the world do you go from here? I remember putting 7 or 8 pounds in it, I wrote it inside the unit. Do I just need to weigh in X percentage more?

  12. #25
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    It's not wrong at all to use subcool. Don't missunderstand. It will give helpfull information but can misslead if relied on as final factor. There are several ways to charge these systems and alot of techs do it different. That doesn't make it wrong it's just different. Experience will teach and you will find what works for you. Keys to remember, full column of liquid at TXV, at least 6 degrees superheat at bulb but no more then 12-15, and be patient. Don't rush this.

  13. #26
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by drife678 View Post
    I always try to check subcooling right at the inlet of the exspansion valve. Wont this tell me if the charge is correct.
    Absolutely. It will tell you if you have a full column of liquid at txv. However if it's a hot day there will be no liquid stacked in cond to keep head pressure up and if you stop at that point there will be no or not enough liquid in the receiver. So as the ambient drops and the head drops the headmaster will start stacking liquid in cond to keep head up. So if you pulled up at a full glass and subcool on a hot day there is no liquid to stack and pressures drop and glass will have bubbles and subcooling will be gone. Subcool should always be checked as should superheat but can mislead on initial charging. Don't kick yourself if you have to go back and add alittle on a 40 degree day we all do it from time to time. As I said experience is the best teacher once you understand what's happening in there.

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