The theory of charging an R22 system without a TXV - Page 2
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  1. #14
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    Sneuberg, click this link for our contractor locator map. http://icemeister.net/aop_map.html

    There is a company in Tucson on the map, and I am sure they have the knowledge and tools to charge systems correctly.

  2. #15
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    New Install Charging

    Just curious,,,

    On a new install, the outdoor unit (in this case Trane xLi16) contained the proper system charge for the complete system (including some amount of linesset)????

    So the install tech brazes everything together, pumps down the lines, and then opens the valves on the outdoor and you're good to go....no extra charge unless lineset is over X feet...

    Is this correct??

  3. #16
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    Quote Originally Posted by wraujr View Post
    Just curious,,,

    On a new install, the outdoor unit (in this case Trane xLi16) contained the proper system charge for the complete system (including some amount of linesset)????

    So the install tech brazes everything together, pumps down the lines, and then opens the valves on the outdoor and you're good to go....no extra charge unless lineset is over X feet...

    Is this correct??
    Unless you have a real short line set, then it has too much refrigerant in it.

    A proper start up should be done instead of racing down the road once the valves are open.
    Beware of advice given by some guy on the Internet.

  4. #17
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    Does 40' of new (so I assume it matches Trane's size requirement) lineset require additional charge??

  5. #18
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    Quote Originally Posted by wraujr View Post
    Does 40' of new (so I assume it matches Trane's size requirement) lineset require additional charge??
    Yes, usually.

    This system has a txv so charge should be verified by subcooling.

  6. #19
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    I will differ with the previous responses somewhat. Where the manufacture tables/ guidelines are unavailable, I was taught to use data from the compressor manufacturer as different compressor MFG's want different things. Remember that we want enough cooling capacity to return to the compressor for the windings.

    Another method where no other data exists would be measurement of system output vs rated capacity (if available) or simply optimizing capacity & efficiency. Most residential techs/clients wouldn't have enough patience for that, but it would serve as a valid method.

    In my mind I would NEVER, NEVER use a weigh in charge as the optimal method on a split system design. Refrigerator, yes. AC? no. While the method certainly exists I've never read a install manual that suggested it is the preferred method for AC, unless we are talking mini splits. I would however use it as a diagnostic tool if necessary.
    What lies behind us and what lies before us are small matters compared to what lies within us.


    Two pressures, four temperatures = SUCCESS!


    Boulder Heating Contractor


    For Consumers:

    For HVACR Professionals:


  7. #20
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    Quote Originally Posted by wraujr View Post
    Just curious,,,

    On a new install, the outdoor unit (in this case Trane xLi16) contained the proper system charge for the complete system (including some amount of linesset)????

    So the install tech brazes everything together, pumps down the lines, and then opens the valves on the outdoor and you're good to go....no extra charge unless lineset is over X feet...

    Is this correct??
    Installation without testing is ALWAYS a bad idea.

    I tell my friends that my customer isn't paying me for equipment, they are paying for me to design, install, and tune a system. Your equipment is in third place next to your contractor in terms of importance.
    What lies behind us and what lies before us are small matters compared to what lies within us.


    Two pressures, four temperatures = SUCCESS!


    Boulder Heating Contractor


    For Consumers:

    For HVACR Professionals:


  8. #21
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    Quote Originally Posted by fearlessfurnace View Post
    if you like english beer beer can cold can be prety close
    A heavy indoor humidity load tosses the beer-can-cold non-sense out the window.

    The outdoor dew point determines at what temp the suction line sweats; that's fools gold methodology...

  9. #22
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    Quote Originally Posted by darctangent View Post
    I will differ with the previous responses somewhat. Where the manufacture tables/ guidelines are unavailable, I was taught to use data from the compressor manufacturer as different compressor MFG's want different things. Remember that we want enough cooling capacity to return to the compressor for the windings.
    On a fixed metering split system where would you go for compressor manufacturer specs? Some days you will have 25 SH and some days only 5 SH

    Another method where no other data exists would be measurement of system output vs rated capacity (if available) or simply optimizing capacity & efficiency. Most residential techs/clients wouldn't have enough patience for that, but it would serve as a valid method.
    This is a great plan! Kind of hard to get the specs sometime, especially when you are not at ARI design conditions.

    In my mind I would NEVER, NEVER use a weigh in charge as the optimal method on a split system design. Refrigerator, yes. AC? no. While the method certainly exists I've never read a install manual that suggested it is the preferred method for AC, unless we are talking mini splits. I would however use it as a diagnostic tool if necessary.
    My comments in red.

    I agree with your last paragraph, too many variables to use weight as the final answer for the correct charge.

  10. #23
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    Quote Originally Posted by wraujr View Post
    Just curious,,,

    On a new install, the outdoor unit (in this case Trane xLi16) contained the proper system charge for the complete system (including some amount of linesset)????

    So the install tech brazes everything together, pumps down the lines, and then opens the valves on the outdoor and you're good to go....no extra charge unless lineset is over X feet...

    Is this correct??
    Always, before the charge is checked the correct airflow through the indoor coil must be checked & confirmed & documented for the customer's records.

  11. #24
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    Quote Originally Posted by chuckcrj View Post
    My comments in red.

    I agree with your last paragraph, too many variables to use weight as the final answer for the correct charge.
    As to the first item-

    If you are looking for a fixed # then you need the condenser to be operating in a fixed environment, and most resi AC condensers have a design condition of 90F ODT. The fixed SH value for a compressor can be had directly from the MFG via support. I don't believe copeland has specs in their product literature but that could have changed. keep in mind that one might be able to play with that figure a little depending on the environment conditions the system is installed in. ie- Yuma and Seattle are two different scenarios.
    What lies behind us and what lies before us are small matters compared to what lies within us.


    Two pressures, four temperatures = SUCCESS!


    Boulder Heating Contractor


    For Consumers:

    For HVACR Professionals:


  12. #25
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    Jun 2011
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    Wake Forest, NC
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    So am I mistaken that most major manufacturers recommend weighing in additional refrigerant on unit start-up. I am almost 100% certain that both Rheem and York on their installation manuals have a supplemental charge section that gives weight by line set size and length.

    I am all for checking the superheat and subcooling on system test to verify proper operation, in fact you would be doing the customer/system a disservice to just weigh in a charge and not verify it. all I'm saying is that the manufacturer recommends weigh-in as their preferred method.
    It's not rocket-science...

    It's electromechanical thermodynamic engineering

  13. #26
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    Moore, Oklahoma, United States
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    On systems that have been in service for a few years how does dirty condensers/evaporator coils factor in?

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