Okay so like some of the other guys on the site, I am new in the refrigeration side of things, Have been doing air conditioning for quite some time. I am stuck in a jam with a freezer that I am working on. Let me explain.
Okay the box is brand new, 10'x18'x6' 4" thick walls, has a walk in door and 6 reach in glass doors on the front.
My condensing unit is a 5 ton, R404A, Has a receiver, sight glass, and a filter/drier installed inside it. Unit is located outside. Outside ambient temp is typically 85-95 *F in the summer.
My indoor coil is a 5 fan evaporator with a 1/2 - 2 ton TXV installed. also R 404A TXV is all the way open.
My indoor coil get frost on it, like snow, and my outside suction line gets heavy icing on it, as well as the compressor. I have bubbles in the sight glass.
I know my problem lies within the undersized TXV and the undercharge, but I would just like to know what is going on with the system, the science behind WHY the compressor is freezing up, ect.
Thank you gentlemen in advance!
Any suggestions are appreciated.
We don't know what the btu rating of the evap coil is. We don't know what powerhead is on the txv. You didn't tell us if the box is at temp. Failed to give us pressures, SH and SC etc. A frozen compressor may be normal. As far as the "science" The "science" is the same as an a/c unit. Freezers aren't magical
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My box gets down to 5-10*F, Seems like it struggles to get down this low, and takes longer than it should. I do not have a model number on the compressor or evap, I will get it as soon as I can. I have a Russel 5 fan evaporator and a Heatcraft condenser. The compressor is a copeland scroll. I am sorry that I do not have any specific information at this time. I was hoping you guys could provide me with some solutions if you can that would help me out.
Thank you
Everything that you just said aside, here are some basics. All of this could be quite normal. You just said that your box temp is 5-10 degf. If you have a 10 degf td that puts the sst at -5 to 5 degf. Your coil and suction line at this temp are going to ice up. This is why we have to use some form of defrost (hot gas or electric), to clear the coil. That being said, there are different types of frost. Normal frosting of the coil surface. Then we have "snow" which is more likely due to warm air infiltration. Lastly, there is ice which is typically a sign of coil flooding. Coming from a/c, frozen pipes probably send up a red flag for you. In low temp refrigeration it can actually be a good sign so long as you know your superheat is good. Also, you said that the sight glass had bubbles, and this is a new install. If you charged to clear sight, you have a receiver, and you are positive that the coil isn't flooding (ie checked superheat at evap), you need to get out your leak detector or bubbles and find your leak. Sometimes, if you are flooding the coil it can appear as if you are low on charge because you have so much liquid out in the system. It would be helpful if you had given us more specifics, but I wanted to throw some of this out there for you to think about before you start changing parts.
Well thank you very much. That makes a whole lot of sense. I also realized that low on charge would make the coil freeze up incorrectly. If that makes sense. Also in undersized txv would be why the refrigerant isn't boiling off properly. I hope I am right with this theory. I will get back to you guys with superheat and sc
Okay I would like to update you guys on my issue. I referenced the compressor and I found out that the other guy was wrong saying that it was a 5 ton. It's btus rating was about 26,000 which would make it about a 2 ton compressor. The txv is correct size an the charge was just about right. Very few bubbles in the sight glass and they went away after running. I found that the defrost heater circuit was not kicking on because the heaters were not wired correctly. I got the heaters to melt the coil and the freezer gets down to temp nicely. The ice was acting as an insulator. So liquid was coming back to my compressor which caused it to freeze up. The box has 6 doors that open and close a lot so I made 6 defrost cycles at equal intervals which seems to be about right. Thanks for your advice gentlemen.
Walk in Freezer Help!!
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Originally Posted by 2sac
