ReplyThis unit had access valves?
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My exsperience is with residential HVAC. I was helping a family member with their refrigerator. The freezer does not get below 20 degrees. I went ahead and recharged the system. It seemed to help a little but not much. The top of the compressor is getting pretty hot. It is a cap tube system. I was kind of in a hurry when I was doing it but I believe that the suction pressure was somewhere around 18 PSI. This seems too high to me. One of my questions is should an R134a system operate with a suction temperature in the vacuum range in order to achieve temperatures cold enough for a freezer. If so I wonder if it could have non condensables in the system.
PS everything else looked normal. Clean condesor, fans working etc
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This unit had access valves?
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No I had to braze a service port onto the process stub.
Last edited by JayMan7; 06-28-2018 at 06:44 PM.
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Besides getting some suggestions on what my be wrong, my main question is... wouldn't 134a have to be at vacuum pressures in order to achieve an evaporator that is cold enough for a freezer. If it is in a vacuum then i wonder if atmospheric air has leaked into the system and is responsible for what is going on.
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Unless you were sure there was a charge issue inttalling valves was a mistake. Too late.
For a 0 deg Freezer you should have a -10 too -20 deg SST. What would the pressure be?
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I agree piercing valves are a mistake, I feel fine about a brazed in access port. Anyway, you're saying 1.97psi to -1.75psi. Hmmm the only thing I can think of that would cause a higher than normal suction besides an overcharge would be non-condensables. What do you think?
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Cap Tubes / R-134A / Plugged condensers lead to restrictions of the cap tube. Was thh spun copper drier changed? If not install a Sporlan 032-CAP-T. Cut off about 6" of the cap tube. evacuate and weigh in new charge.
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Thanks that does look like a good filter dryer to use and would provide a high side port! I got to thinking about it more and I wonder if the compressor is going bad. If a bad valve or ring was letting discharge gas blow by it could cause the compressor to run hot like it was and raise the suction pressure. It's just hard to say. These small systems are built to throw away not to service.
I think what is bothering me the most is the high suction pressure. I feel like there's only really 3 things that could exsplain it. Overcharge (unlikely), non-condensables (possible), and bad compressor.
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What led you to believe the system needed recharging? Was there a leak? A leak in a residential refer usually means get a new one.
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Or the new C-052-CAP-T-HH. Apparently picks up wax.Originally Posted by pecmsg
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If charge is correct & your SST is higher than Design ,, I’d say Compressor has lost Effiency.
The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.
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I agree, I think I'm calling the compressor on this one. It's probably like a $4000 fridge but since it's an LG and has some age on it I don't think we're going to put any money into fixing it.
"I think Quantum tunneling would work great...
"Call a technician for God's sake. Or we'll see you on the news or the Dark Side of the Moon."
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Depending on the client , I’d say a compressor could be purchased for around 150$’s AU.
The primary function of the design engineer is to make things difficult for the fabricator and impossible for the serviceman.
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So you had a sealed system. You did the right thing to install a low side access valve, and you found the problem - suction pressure way too high.
Yes, they run in a slight vacuum. But if the unit had a leak and was sucking in air, it would cease to suck in air once suction pressure got to 1psi Then it would leak back out. It didnt suck air up to 18 psi of positive pressure.
Since it was a sealed system that used to work that now has high suction, we KNOW it is not overcharged, noncondensibles, restricted capillary tube, low on refrigerant, incorrect drier.
You are correct suction pressure will start out around 5-7 and get down to 0 or slightly below when box at temp.
The compressor is inefficient. I changed an LG residential unit compressor in the last year. I was shocked the compressor was less than $200.
I disagree with putting oversized driers. The units hold 3-4 oz of refrigerant. A C052 drier holds more than that. Maybe i could see using a C032. But personally i went back with a bullet drier like original. After repair, weigh in nameplate charge, pinch off high side, bleed refrigerant from my hose back into low side, and braze lines closed. Has been working flawlessly for almost a year now. no reason to buy a new $4000 fridge.
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Thank you for that responce... definitely the most inforamative so far! And has given me some really good things to consider. I'll provide an update once I find out for sure what the owner wants to do.
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it doesn't matter if you pay 500 or 5000 for the LG .... they all have the same crappy refrigeration now
You see , they finally got smart , because refriges used to last 40 years , so they had to wait friggin 40 years to make another sale !
Now they are designed to last 5 years .... do the math
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