Today I was working on walk in cooler... I put my guages on and found that my high side goes up and down... I was told that previous tech was here last week and he changed the compressor. I noticed that he did not change filter drier. He probably didnt even pull vaccum. I was told when my gauges do this I have air or moisture in my system... What should I do? How long will this unit last before something happens.. What will happen?
non condensbales in refrigeration system
otto8
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If as you stated the last tech didn't pull a vacuum and didn't change the drier At the least there will be non cond. in system. As far as a leak did you find one?
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otto8
How did you know to stop charging?
What measure did you use?
How did you know to stop charging?
What measure did you use?
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I'm anxious to hear their reply too. I thought this was an educational forum, not an attack forum.ar_hvac_man, Can you please list numbers of reasons why head pressure would flactuate... I dont need anything else to know... You dont need details. List some of the reasons why would head pressure flactuate.. Thanks
#1CDNTECH, I found pressures low. Charged unit. Looked for leaks. Didnt find it. Now I just want to know why my head pressure is flactuating... There is no fan cycle. Fan runs all the time. Hmm is there anything else you need to know... Oh yea i checked if my condesor is clean.. Yup... Condensor looks good no restricion.... Very good... Looks like previous tech was in hurry to leave the job. It was probably late.. Hhmmm anything else you need to know?? I HAVE BEEN TOLD DIFFERENT REASONS FOR MY HEAD PRESSURE TO FLACTUATE... Can you be please so kind and tell me few reasons why it flactuates... Thanks man!
One would have to see what he saw. Most walk-in compressors have pistons that go up and down. Sometimes that alone is enough to make the neddle on your gauge fluctuate.
Then you have an expansion valve. It will modulate as needed to maintain superheat. That could make you head pressure change some too. So could changing load conditions in the walk-in. You can often tell when someone opens a door just by watching your gauges. At some point condenser fans should cycle and that will change head pressure.
So really there are too many reasons and without seeing what you saw nobody can do more than make a guess. The guys in this forum are very helpful provided your posts show a reasonable understanding of basic principles.
Non-condensables can be tested for. Basically you pump down system and allow the refrigerant to reach ambient air temperature and then look at gauge pressure and compare to chart values for that temp. Moisture will often cause ice at the TXV and prevent it from working correctly. The sight glass should have an indicator. If a problem is suspected you should test the oil for acid. Good practice dictates replacing the filter/dryer anytime the system is opened.
Then you have an expansion valve. It will modulate as needed to maintain superheat. That could make you head pressure change some too. So could changing load conditions in the walk-in. You can often tell when someone opens a door just by watching your gauges. At some point condenser fans should cycle and that will change head pressure.
So really there are too many reasons and without seeing what you saw nobody can do more than make a guess. The guys in this forum are very helpful provided your posts show a reasonable understanding of basic principles.
Non-condensables can be tested for. Basically you pump down system and allow the refrigerant to reach ambient air temperature and then look at gauge pressure and compare to chart values for that temp. Moisture will often cause ice at the TXV and prevent it from working correctly. The sight glass should have an indicator. If a problem is suspected you should test the oil for acid. Good practice dictates replacing the filter/dryer anytime the system is opened.
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I wasnt attacking the guy. Were just not allowed to give in-depth technical info to DIY'ers, its against the rules.
That being said I did give several possible reasons and others have told how to check for non-condensibles. I see head pressure flucuating all the time even with perfectly running equipment.
Otto: Does it have a sight glass and what did you see in the glass? What was your superheat at the evaporator? What was your subcooling?
My superheat was 11..... A lot of times I use TP chart when charging my system. I have been told to use the rule of 30+ abient temp.... I dont know if you guys use that when checking if your system is proparly charged.... I really didnt need help on this jobs.... I just wanted to know why my headpressure kept jumping up and down. I was afraid that I put air or mouister in system and I will mass this unit up lol I gave few deatils and it went into different discusion...THANKS TO ALL OF YOU FOR YOUR HELP....
I gave few deatils and it went into different discusion...THANKS TO ALL OF YOU FOR YOUR HELP....
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A walk-in cooler will typically have a receiver AND a sight glass.
If the unit is outside in low ambient conditions, it will also have a headmaster or other low ambient control means.
If you do not at least charge to a full sight glass, you are undercharged. If you have the low ambient controls, there is a series of computations you must complete to be properly charged.
Throw "ambient plus 30" of any other rules of thumb you've been taught away.
If the unit is outside in low ambient conditions, it will also have a headmaster or other low ambient control means.
If you do not at least charge to a full sight glass, you are undercharged. If you have the low ambient controls, there is a series of computations you must complete to be properly charged.
Throw "ambient plus 30" of any other rules of thumb you've been taught away.
Coilcleaner, I didnt find leak... The man before me just rushed to get the job done and didnt even charged the unit right.... So I had to go back there and stay 5 hours and complete the job... Cooler works fine... I was just freaking out about high side jumping up and down... Thanks for you help tho ) All of you guys are helping me.. I have learned a lot here... None of you will ever offend me... I am here to learn
) All of you guys are helping me.. I have learned a lot here... None of you will ever offend me... I am here to learn
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SOOOOO is head pressure still unstable? Did you say this had a txv?
jpsmith1cm, u r right... I have been thought that rule when I did residential installs with old school guys who didnt care about super heat or sub cooling..If you suction line is cold and fan is putting out hot air u did it right they would tell me LOL...
Now, I dont know what you will say about this, but I was told by our techs who have more experience that... If you got txv and sight glass on a walk in cooler u cant rely on that sight glass it will always bubble because of the way txv works... Super heat or sub cooling is the best way... What do you think about that ?? Is that true statement..
Now, I dont know what you will say about this, but I was told by our techs who have more experience that... If you got txv and sight glass on a walk in cooler u cant rely on that sight glass it will always bubble because of the way txv works... Super heat or sub cooling is the best way... What do you think about that ?? Is that true statement..
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Utter rubbish!otto8 said:
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Mabye you have a flat head or malfunctioning txv.
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First and foremost, you MUST have a solid column of liquid to the TXV. A bubbling sight glass says that you do not.
Please keep in mind that I am talking about TXV systems WITH a receiver.
Those without a receiver should be charged to subcooling or by weight.
Please keep in mind that I am talking about TXV systems WITH a receiver.
Those without a receiver should be charged to subcooling or by weight.
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Torch the receiver
ar_hvac_man, yes there is sight glass and I charged the unit until there was no bubbles. There is no indicator on sight glass.... Just one of them cheap ones that u can see liquid. My superheat was 11.. I didnt check subcooling.... I hope I did that right
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