Superheat Cap Tube Systems
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  1. #1
    Join Date
    Jul 2005
    Location
    Phoenix, AZ
    Posts
    265

    Superheat Cap Tube Systems

    When taking superheat on a cap tube system, reach-in, or prep table with a cap tube. Where is the proper place to measure suction line temperature. I have seen guys measure it 3 inches away from the compressor on the suction line. This is taking compressor superheat or total system superheat I am assuming. But where is the proper place to take temperature on the suction line on small self contained systems with a cap tube to verify proper performance. Some clarification would be greatly appreciated.

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  2. #2
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,308
    Most of these systems have the cap tube soldered to the suction line. In these cases you have to take the superheat before the heat exchange area (closer to the evaporator).

    I never check superheat on these things, but thats just me. On small cap tube systems I do almost all my refrigerant diagnosis by feeling the condenser return bends.

    After you've felt enough properly working systems, you know what they're supposed to feel like at different points. If I then suspect something is wrong, I'll throw on a low side gauge (usually this requires adding a piercing valve). I don't like adding a high side gauge unless farther diagnosis is necessary because you loose too much refrigerant.

  3. #3
    Join Date
    Jul 2005
    Location
    Phoenix, AZ
    Posts
    265
    What kind of superheat should you expect when the cap tube system is operating properly? 15-30 degrees?

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  4. #4
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by phxhvac View Post
    What kind of superheat should you expect when the cap tube system is operating properly? 15-30 degrees?

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    What ever the minimum SH the comp manufacturer requires. Since its a fixed orifice with no adjustment that's all u would use it for. If it has a receiver weigh in the charge. If no receiver check subcool.

  5. #5
    To tuff to tell.its all over the place they usually all have accumulators rite out the end of evap.da pressures are tuff to on them sobz! Gauges suck up ref wit long hoses no homo! Give u flase readings ! Do amp draw dollar charge new drier an look at captube for wax buildup if present cut back some if still there **** can it get a spliff on a new sale or b a fool an hack the **** out of it replacing cap tube condensing unit an drillin out accumulator for contaminate oil

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