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  1. #1
    Join Date
    Aug 2006
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    Canada
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    Capillary tube sizing


    Hi All. This is my first post. I have away from the trade for 10 years, and am having trouble with the new refrigerants. I hope someone can help me.

    My situation is as follows:
    I have a freezer (1525 btu) that was designed on R12, running a tecumseh tin can, cap tube system. The refrigerant was changed at some point in the past, and apparently many technicians have looked at this with minimal success in making it work.

    I am not 100% certain what refrigerant has been dropped into this thing, but I am guessing 409a , however it is acting like there is a restriction. I am running 150# head, and 6# suction, with a 74f liquid line and a 40f suction. I am interpreting this system as having 38f subcooling in my LL and 40f SH. I can't get the box temp below 40f and with the 40f superheat, my evap is starving.

    There isn't a TD across my LL filter drier, so I am ruling out that it is plugged (however I will be replacing it when I open the system).

    I am viewing the cap tube as the culprit, and have been attempting to determine;

    1./ What size and length should it be for this system.
    2./ For the future, what impact will changing refrigerants have on cap tube sizing

    I have spent the day on the net researching this and have obtained contradictory information. According to an engineering study posted on scienceasia.tiac.or , R12 requires a longer cap tube than R409A.
    According to Supco exactly the opposite is true. (taken from the sizing charts in their catalogue)
    The danfoss cap tube part sizing chart bears almost no similarity to the rest in terms of sizing and length relating to capacity.
    The trade text "Modern Refrigeration and Air Conditioning" by Althouse posts a chart that doesnt go as high in terms of capacity as the rest, however they have different sizing relationships again.

    I realize that I can simply try it out and shorten the tube until I get some performance that will be acceptable, however I would prefer to approach this with a full uunderstanding, rather than a trial and error. If this is a consideration for future retrofits, I would like to know this going in. If I am missing something I would like to know that too.

    The main sources I have found I have listed below. Sorry... as a new member I cannot post links.

    scienceasia
    danfoss
    Supco
    Modern Refrigeration and Air Conditioning text by Althouse.



  2. #2
    Join Date
    Oct 2001
    Location
    Nottingham UK
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    Re: Capillary tube sizing

    Hi Sledge and welcome to the forum.
    Here's a link to the first post I made on this forum back in 2001.
    http://www.refrigeration-engineer.co...cked+capillary

    Also, you can use the Search button above for like minded posts
    I'm back on the Pale

  3. #3
    Join Date
    Jan 2009
    Location
    jax, fl,
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    Re: Capillary tube sizing

    get a sporlan txv built at your local sporlan dealer. internally equalized with a z charge in the powerhead and get rid of that cap tube. change the drier, put on a sightglass, evacuate it and recharge it with hot shot. you will be all in there.

  4. #4
    Join Date
    Mar 2001
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    Dorset
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    Re: Capillary tube sizing

    Quote Originally Posted by hd88 View Post
    get a sporlan txv built at your local sporlan dealer. internally equalized with a z charge in the powerhead and get rid of that cap tube. change the drier, put on a sightglass, evacuate it and recharge it with hot shot. you will be all in there.
    Maybe if you had joined and posted two and a half years ago, when the original question was asked, then it might carry more weight.
    Brian - Torquay, Devon, UK
    I have to stop saying "how stupid can you be?" to my co-workers.
    They're starting to take it as a challenge...

    BASIC MAINTENANCE. If it doesn't move and it should then use WD40. If it moves but it shouldn't then use Duct Tape.

  5. #5
    Join Date
    Dec 2008
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    USA
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    Re: Capillary tube sizing

    haha he told you !!!!

  6. #6
    Join Date
    Jan 2009
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    jax, fl,
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    Re: Capillary tube sizing

    yeah how lame is it to have this stuff posted this long. yeah i guess he did tell me, alot about himself!!!!!!!!!!!!!!!!

  7. #7
    Join Date
    Nov 2008
    Location
    Indonesia
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    Re: Capillary tube sizing

    Frank, if I am experiencing these events.
    I heat the evaporator with a heat weld.
    ago I was doing vaccum before filling refrigerant.
    Last edited by James priyono; 30-05-2010 at 03:02 PM.

  8. #8
    Join Date
    Nov 2010
    Location
    Staten Island
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    Re: Capillary tube sizing

    Hey people this is my first post, gotta say quite the smart bunch we got here. Anywho, my simple problem is as follows, got an upright old as time delfield freezer, tecumseh comp, was made for R12, however R 401B was put in, TXV was removed and replaced by a cap tube, say bout 2ft in length. Just want to know what size tube should be in there, also would the original TXV (R12) work should i remove the captube?

    NYChvacguy

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