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  1. #1
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144

    R 134A superheat on ????????

    ?????? is a home refrigerator. Come on guys, I know you hate waisting time on refrigerators, but i figure it is all educational. I haven't put a tap on this thing yet, but am going to tomorrow. The suction line temp is 65 degrees. the unit cools fine, but runs constantly. I do not have a sticker on this refrigerator to tell me the weigh in or that is what I would do. I know that with the box cool, I should be around 0 to 1 degree on the suction. What should I shoot for on the superheat?
    Thanks guys!
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  2. #2
    Join Date
    Jul 2007
    Location
    Tulsa, OK
    Posts
    986
    Hot box - 13' S/H

  3. #3
    Join Date
    Jul 2007
    Location
    regina saskatchewan
    Posts
    257
    if no plaque showing charge,check superheat when box is down to temp.10 degrees SH would probably be fine.
    Artificial Intelligence is no match for Natural Stupidity

  4. #4
    Join Date
    Jun 2006
    Location
    Omaha, Nebraska
    Posts
    861
    Since the cap tube is probably soldered to the suction line it going to be pretty hard to get much lower than 60 Degrees SH at the comp. I hate to say this, but maybe charge it by RLA?

  5. #5
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144
    Guys, on A/C units I understand the refrigeration cycle pretty much to a T. I have a learning curb on refrigeration, even though the cycle is the same. I am trying to learn here, so help me if you can. I want to add that I really think that it is worth learning about refrigerators as it should relate to some equipment in commercial facilities, and I think that there will be a market for residential service on these $1100-$2200 stainless steel units being sold today.

    I have the numbers to follow: When I first hooked up, I had a 2 psi suction pressure and a 65 degree suction line temp. Again, this is 134a. I didn't install a tap on the high side. I was amping at 1.1 on the compressor.
    Ok, so I bump in some 134a. I get the pressure up to 4 and the line temp down to about 35. The amp draw didn't seem to change too much. To me, these numbers should be good. However, I decided to try to locate the sticker 1 more time to find the weigh in charge, and I did locate it. It says it holds 4.5 ounces and amps at 11.6.
    I triple vacuumed the unit and weighed in 4.5 ounces as a liquid. I came up with 1 psi and 57 line temp. The amp draw on the refrigerator as a whole is 2 amps.
    Now, as I stated before, the refrigerator/freezer is working fine, it just runs a lot. What I am not understanding is why are the 4 psi and 35 line temp numbers not better than what the manufacturer's weigh in came up with? I know that I probably had a higher head at these numbers, but the liquid line felt like it was around 80-90 degrees or so, which should be a decent subcool considering the small coil size.

    What is going on here. Should I leave it as is, or bump in some more refrigerant to bring the line temp back down? After being turned off for about 1.5 hours and the doors opened a couple of times, the refrigerator just satisfied after being on for about 45 minutes after charging it.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  6. #6
    Join Date
    Sep 2002
    Posts
    12,568

    First thing = clean the condenser spotless

    .
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  7. #7
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144
    Quote Originally Posted by Poodle Head Mikey View Post
    .
    I cleaned it the other day.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  8. #8
    Join Date
    Sep 2002
    Posts
    12,568

    OK then -

    Seems to me that if you have clean coils, fans working, low suction pressure, and the proper charge, and the unit is running too long - then you are gaining too much heat.

    How are the door gaskets? Sealed well on all four sides?

    Do the lights go off when you close the doors?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  9. #9
    Join Date
    Aug 2007
    Location
    Winter Haven, FL
    Posts
    4,379
    You have 77 degrees of superheat. You are not bringing enough refrigerant back to the compressor.
    Did you add refrigerant to compensate for the hoses on your guages? A 6 foot hose holds approx 1 oz.
    When charging a very small volume like that is better to use a charging cylinder with a 1 foot hose. Then use stub guages to take measurments.

  10. #10
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    6,006
    Don't even think about persecuting this procedure. Add vapor in small amounts until it frosts back to the compressor when the box is near set point. release refrigerant until the frost is within 6" of the compressor. This takes a little time, but is tried and true for decades on small household refrigerator/freezers. This of course only works if the cap tube is not restricted or if there are no other problems like the defrost heater being on or evap fan not working.
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  11. #11
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144
    Quote Originally Posted by Joe Harper View Post
    You have 77 degrees of superheat. You are not bringing enough refrigerant back to the compressor.
    Did you add refrigerant to compensate for the hoses on your guages? A 6 foot hose holds approx 1 oz.
    When charging a very small volume like that is better to use a charging cylinder with a 1 foot hose. Then use stub guages to take measurments.
    This is a tricky part of weighing in as you say. What I do (and I don't know if this is right) is after I have reached my weigh in amount, I flip the jug over and and charge with vapor until I see the needle smooth out, which indicates to me that there is no liquid present in the lines. With that being stated, I am not sure if this ensures no liquid in the guage lines to the unit, or just up to the point of the gauge. It takes a couple of seconds, which is longer than it takes to bleed the charge line when I am purging the lines of air, so I assume my theory of doing this should work. Feel free to "Weigh in" (pardon the pun) on this practice guys.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  12. #12
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144
    Quote Originally Posted by rayr View Post
    Don't even think about persecuting this procedure. Add vapor in small amounts until it frosts back to the compressor when the box is near set point. release refrigerant until the frost is within 6" of the compressor. This takes a little time, but is tried and true for decades on small household refrigerator/freezers. This of course only works if the cap tube is not restricted or if there are no other problems like the defrost heater being on or evap fan not working.
    So are you saying that I am looking for a temp of around 33 degrees on the line at the compressor? I had this yesterday before I dumped the charge and weighed it in. I was unsure if I should be frosting at the compressor or not, but I felt a whole lot better about the numbers(as was shown in a previous post here) that I was with the 57 degree temp.
    Also, I thought that 134a had to be charged as a liquid because it is a blend. Is this not true?

    Basically, from what I am seeing here, I should be around 3 psi and a 33-35 degree line temp. Is this correct? Also, why am I getting such a low amp draw? I am taking this reading where the cord hooks to the unit, so I know it is all she is drawing. This tells me at least that I don't have a high head, and that helps determine that there is no restriction at least.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  13. #13
    Join Date
    Jun 2006
    Location
    Omaha, Nebraska
    Posts
    861
    If you got that larger amp rating from the sticker on the fridge it is probably for the heaters. They draw more in defrost than in refrigeration. I would try to find the RLA of the compressor only.

    But charging to 35 Degrees at the comp is going to get you darn close.

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