View Full Version : Home refrigerator-R134a
08-06-2010, 05:54 PM
I am checking out my home refrigerator which uses R134a. I am running at 3 psi and the line temp is running at 36 with a 2 degree box temp. I am going to let it cool on down, but the reason I desided to check it out on the pressures is that the it was time to clean the coil, and I noticed that the suction line was frosted over, and then it would thaw a little. When I first hooked up, the line temp was right at 32.
Anyway, right now I am figuring that I have around 40 degrees superheat. The box is still pulling down, so I am not adding anything yet.
What superheat should I run on a home refrigerator? I think last year when the box settled out I was at about maybe 2 psi and a fluctuating SL temp of about 18 degrees to 32 degrees. Should I be charging it that low on the LL temp? If so, I need to add some insulation to it.
08-06-2010, 07:26 PM
Well, the box temp is hanging around 2.7 degrees, the suction is 3.7 or so psi, and the suction line temp is between 18 and 20. So I am at about a 24-26 degree superheat. I think there may be some load on the unit from some food we put in today.
Does this sound alright? Seems like the box was getting on down to around 0 last year, but with the load from the food, and the fact that my wife has the house at about 78 degrees today because she is cold natured, I think it is alright. Just wanting another opinion.
08-06-2010, 07:46 PM
Around 5 psig on the suction line should be good. Let it pull down and and open the door and watch what happens.
I think what you posted is good.
I sucked 1/2 of a Ladies Cat out of one two weeks ago but it didn't survive. Yea, the 'fridge. It was tripping out on high temp. I don't think the thermostat had been controlling the temp for a long time just tripping out. After I removed 1/2 of her Kitty it still wouldn't cool.
08-06-2010, 11:59 PM
If you have added or removed freon, you need to totally pull the charge and weigh it back in. Thats a cap tube system, and you're wasting your time trying to charge it any other way. The proper charge should be listed on the Model number label. If your still having problems after weighing in the proper charge, then you need to look for other problems. I'm not trying to be smart, just worked on too many domestic units.
08-07-2010, 03:17 AM
Make sure all the air ducts are clear and that your evaporator fan motor is running full speed. Also most domestic refrigerators that I worked on( I was a domestic guy for 27 years) had the liquid line soft soldered to the suction line, if that solder fails your suction line will frost. Check your door seals too, a bad fresh food section door seal will give long run cycles and get the freezer too cold and could cause a frosted suction line. As far as superheat let me tell you what a customer of mine who worked at GE on the assembly line making refrigerators told me. They would charge the system and let it run till it frosted back to the compressor, then they would let vapor out till the frostline moved back to where the suction line came out of the cabinet. Before EPA rules I used to do that myself it was called charging by frostline. That wouldn't work today, those old systems had accumulators and 18 to20 ounces of R12 New refrigerators have 3 or 4 ounces of 134A. Don't forget that is a cap tube system, there is no txv to control superheat. So your superheat is going to be different at the beginning of a cooling cycle when the most load is there.
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