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  1. #1
    Join Date
    Jul 2008
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    "Splicing" cap tube

    Small under counter reach in with cap tube broken about half length from rub through- actually snapped in hand when handled. So then- rather then open up supply house after hours for some bullet cap- I decided to experiment- why not. Just coupled it together with 1/4". The only "problems" I noted despite seemingly lower than normal suction and elevated high side. What kind of problems can I expect from my so called experiment- and that raises another question that I never understood- we determine the length and size of cap tube by the compressor capacity ok got that- but why the length when it's essentially just an elongated fixed orifice? I mean how does the length determine the pressure drop across/through it? The size (physical diameter) I can see but why is the length so critical and what can happen by "splicing" two ends with 1/4" or what have you?
    "It's just like it doesn't work. I mean it seems to be ok now, but it usually like never works"

    "Never an always and always a maybe"

  2. #2
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    Oct 2016
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    Iowa, USA
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    Following... I haven't come across this but hey! Always learning

    sent using crapatalk

  3. #3
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    Oct 2011
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    Harrisburg, NC
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    I've done it. Crimp the 1/4 down around it a bit and never had an issue.


    Sent from my iPhone using Tapatalk

    I can't fix it if it won't stay broke..

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  5. #4
    Join Date
    Jul 2012
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    WA
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    I would expect it to work fine. Length is critical because of the resistance to flow. The more length, the more resistance.

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  7. #5
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    Jul 2008
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    Thread Starter
    Quote Originally Posted by CRussell1975 View Post
    I've done it. Crimp the 1/4 down around it a bit and never had an issue.



    Sent from my iPhone using Tapatalk
    Should've thought of crimping it down more but i just crimped the end and used a very small piece no bigger then a coupling. I would expect to see some frosting or ice buildup there if there was gonna be an issue
    "It's just like it doesn't work. I mean it seems to be ok now, but it usually like never works"

    "Never an always and always a maybe"

  8. #6
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    Jul 2008
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    Thread Starter
    What troubles me is the abnormally low suction and elevated head

  9. #7
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    Sep 2005
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    Atlanta GA area
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    I would be concerned the ends of the cap tube might be pinched... the hole was not as large as it needed to be.

    Crimping is good... it allows you to be very sparing with brazing... so the cap tube does not get clogged.

    I prefer to replace one when I can... just because... however I understand the supply house being closed.
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

  10. #8
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    Jul 2008
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    Thread Starter
    Quote Originally Posted by ga-hvac-tech View Post
    I would be concerned the ends of the cap tube might be pinched... the hole was not as large as it needed to be.

    Crimping is good... it allows you to be very sparing with brazing... so the cap tube does not get clogged.

    I prefer to replace one when I can... just because... however I understand the supply house being closed.
    Thought of that- clean cut the two tail ends and reamed with knife like we normally would

  11. #9
    Join Date
    Apr 2010
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    California
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    Quote Originally Posted by dave1234 View Post
    What kind of problems can I expect from my so called experiment- and that raises another question that I never understood- we determine the length and size of cap tube by the compressor capacity ok got that- but why the length when it's essentially just an elongated fixed orifice?

    The Cap Tube (ie. Metering Device) I.D., and Length are determined by the A/C Unit Design Engineer's, at the factory, (much like the suction and discharge line set diameter's), for maximum unit performance. I have spliced them together before, with good success as long as you did not get any solder, or other foreign material in the tube's, and got the 2 half's matched up, you should not have any restriction at that splice, that could cause any problems. PS: I don't know why your's broke, but most cap problems occur in the last few inche's of the tubes, usually caused by compressor oil degragation, and compressor motor winding varnish breakdown, IME

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  13. #10
    Join Date
    Oct 2012
    Location
    riverside calif
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    I rub oil some oil on ends of cap tube and then pinch to avoid getting solder on them



    Sent from the van with the a/c on.
    Sent from the van with the a/c on.

  14. #11
    Join Date
    Mar 2015
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    Medford, N.Y.
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    I was taught that back in 72' or so. And you are not allowed to "butt" the two ends together. The two ends could be offset a little, possibly blocking each others flow.

  15. #12
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  17. #13
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    Sep 2002
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    Virginia
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    Thats how ive done several ^ ^ ^ ^

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