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Joined: 3/4/2010(UTC)
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Hey all,
we have an old Kelvinator commercial freezer that keeps acting strangely.
About 4 months ago, I replaced the defrost thermostat as it would not go into defrost. At that time I pulled the unit down into a vacuum and recharged with the required 22 oz R-404A
4 months later, I have ice blocks building up around the outlet side to the TXV (thermal expansion valve) and frost buildup on the lower portion of the evaporator. Had to thaw it all out tonight and it took some time!
Now, the defrost cycle is good, heating coils functioning and unit goes in and out of defrost fine. I just have all that ice buildup in that one area of the TXV and it spreads to the upper portion of the evaporator.
Your thoughts? Bad TXV or maybe I am going low on charge via slow leak?
Thanks
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Rank: Advanced Member
Groups: Senior Expert
Joined: 8/16/2007(UTC)
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Blocks of clear ice are an indication of a restriction in the line. Sometimes you can "clear" the resriction by allowing the unit to defrost completely for 24 to 48 hours. Then the "surge of turning it back on may force the restriction to clear. Other times, it is necessary to evacuate and purge the system, then recharge it. The age of the appliance, and your particular attachment to it will determine the value of doing this.
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Rank: Advanced Member
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Joined: 9/10/2007(UTC)
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So you have a Shrader valve instead of a capillary line. The valve may have a partial oil restriction. Sometimes they can be cleared by using a propane torch on it while the compreessor is running.
With a capillary system, I would saw the line in half with a file, clear both capillary ends with a pin, and drive the oil out with nitrogen, or in the old days before the Montreal Protocol, with R22.
Symptoms of a partial capillary restriction are a lower than nomal compressor current draw, and a hot compressor, but cool condenser.
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Rank: Member
Groups: Registered
Joined: 3/4/2010(UTC)
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This thing has been a bear.
We recharged it with the normal charge and design pressure of the Condensor and the head pressure was sky high! Like 450 PSI!
I had to purge about 4 oz to get a nice frost line to build up.
So far, it is holding temps to around 3 degrees and everything seems to be working as it should, save for the fact that I can see the ice starting to build up, slowly, around the same area again. As the door is opened and closed by the kitchen personnel, the outside humidity gets in and over time, the ice becomes a block.
They are cheap around here in the Fedgov, especially our place. They'll have us fix it until it simply won't run anymore, so I have NO choice but to try to follow your guidelines per restriction at the TXV and perhaps just buy another TXV for it. Problem is, the TXV is so old, you can no longer even see the part numbers on it. I wonder how to get a good match.
Any ideas?
Thanks!
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Rank: Advanced Member
Groups: Senior Expert
Joined: 9/10/2007(UTC)
Posts: 9,586
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You have a defrost problem. Do you have a hot gas defrost with a coil driven valve?
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Rank: Member
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I changed the bimetal switch and it enters the defrost cycle, fine. It uses 'oven style' electric heating elements which do heat up and melt most of the ice away.
The frost/ice buildup is right after the outlet of the TXV, as though there is a restriction, somehow. Unfortunately, this is not an area where the heating elements are located.
The TXV cap line and bulb run up along and are mounted higher on the evaporator -The bulb and line are rusty. IMHO, the bulb charge may have leaked out causing the TXV to not open and close properly.
I may have to get another TXV, but don't know which kind to get as the old one has no markings or indications on it, the unit is so old.
Any ideas on how to match and old TXV with a new one? Unit is R 404-A
Thanks!
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Rank: Advanced Member
Groups: Senior Expert
Joined: 9/10/2007(UTC)
Posts: 9,586
Was thanked: 2 time(s) in 2 post(s)
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Your high pressure is way too high, more like a test pressure, I am confused, I thoght you have a shrader valve, you probably have a capillary line. I would clean it out as I proposed before by sawing the line, and purge the system well down below 30 pd.vacumm.
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Rank: Member
Groups: Registered
Joined: 3/4/2010(UTC)
Posts: 5
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Ice build up again. I
recovered/evacuated and pulled down to 30" HG. It held. This time, blew system out with Nitrogen and installed a new filter drier. Took the old TXV down to APED and they matched it up. Reinstalled, no problems, So far, so good!
I think you were right in that there was some kind of restriction in the TXV. Oil, moisture, who knows...
Thanks for all your help.:)
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