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  1. #1
    Join Date
    Sep 2011
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    12

    A rheem chart that doesnt make any sense

    I'm still trying to figure out the attached Rheem chart.

    How can this chart be right?

    Thanks.
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  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,058
    What are you trying to figure out. It is a heat pump charging chart that tells you at an outside temperatue your pressures and temperature of your refrigerant will be XXX

  3. #3
    Join Date
    Sep 2011
    Posts
    12
    Quote Originally Posted by second opinion View Post
    What are you trying to figure out. It is a heat pump charging chart that tells you at an outside temperatue your pressures and temperature of your refrigerant will be XXX
    I have a hard time believing the chart. The chart says if I have 60psig and an outdoor ambient of 70f my suction line temp should be 76f!

    I must be missing something, my suction line temp is around 40f (beer can cold) - like it should be. This chart makes no sense!

  4. #4
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,376
    More information is needed to decide if the chart is incorrect. Why do you feel 6F superheat is correct?

    40F is to warm for beer anyway and many times for a suction line in comfort cooling.
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  5. #5
    Join Date
    Sep 2011
    Posts
    12
    Quote Originally Posted by comfortdoc View Post
    More information is needed to decide if the chart is incorrect. Why do you feel 6F superheat is correct?

    40F is to warm for beer anyway and many times for a suction line in comfort cooling.
    I agree, 40F is to warm for beer.

    40F was approximate, its probably more like 38F (4F superheat).

    Either way, how can the chart say it should be 76F.

    Who believe's this chart and why?

  6. #6
    Join Date
    Sep 2010
    Location
    Florida
    Posts
    88
    Apparently, Rheem likes more superheat than you do, but I have to agree it seems odd.

  7. #7
    Join Date
    Sep 2011
    Posts
    12
    Quote Originally Posted by captain123 View Post
    Apparently, Rheem likes more superheat than you do, but I have to agree it seems odd.
    Using 60psig (34F) the chart seems to suggest Rheem likes 42 of superheat? Really?

    I don't buy it!

  8. #8
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,376
    What are Return DB and WB temps?
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,776
    Rheem is notorious for using the least amount of refrigerant as possible.

    That said. The chart is presuming X amount of indoor humidity. Look at it for 90 degree outdoor temp and 60PSIG suction pressure, they want a 59 degree vapor line temp. thats because the indoor humidity is down.
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  10. #10
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    first time seeing a rheem charging chart???


    they are different
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  11. #11
    Join Date
    Dec 2009
    Location
    Fort Worth, Texas
    Posts
    151
    install a txv and then you want have to worry about it.

  12. #12
    Join Date
    Sep 2011
    Posts
    12
    Quote Originally Posted by beenthere View Post
    Rheem is notorious for using the least amount of refrigerant as possible.

    That said. The chart is presuming X amount of indoor humidity. Look at it for 90 degree outdoor temp and 60PSIG suction pressure, they want a 59 degree vapor line temp. thats because the indoor humidity is down.
    Does a 120oz (9x5) accumlator play into this in some way?

    I'm seeing a mismatch of the equipment to the model # on the chart. It says its a PCA-030, but the compressor looks like its from a PGA-030. I'm wondering if the original contractor put the wrong cover on it. They used quick-connects, but then brazed about 4 inches after the QC's - almost as if it was cut out after a Quick-connect and reinstalled at a different location. Customer says its original equipment on a new house. I also think the lineset was installed backwards - the service taps are next to the evaporator, but they added a low side (only) service port at the condenser.

    It has a small leak but in heating it appears to be overcharged (355psig).

    I think I'll walk away and wait for the customer to call when the compressor burns-out. The crankcase heater has failed (infinity ohms). I can't rely on the chart and I dont know if the high preassure is caused by non-condensables. I've not worked on a lot (only of few) of these old Rheem systems so I admit I'm in over my head.

    Sure would appreciate some input from an old rheem tech on how to interpert this chart. From what I read of the chart the suction line would NEVER be colder than 50f until the outdoor temp was over 100f (something we dont see in the Northwest) and superheat's would always be very high.

    I dont think the customer will pay to install TXV's - and I'm not up to the taks either.

    Thanks everyone for the suggestions.

  13. #13
    Join Date
    Sep 2011
    Posts
    12
    This jobs done. I thought I'd close this thread with final results and what I learned. First, on these old splits, Rheem uses the smallest amount of refigerent possible - which is why you see high superheat on the charging charts. I used the iwbX3-80-odb formula and calculated a target SH of 29. After recovering several ounces I reached a sh of 26 - close enough for me. My head pressure droped from 355 to nice 275psig in heating. So I'm happy with the final charge - and YES, it was overcharged! Thanks to everyone that offered a useful suggestion. And to the other trolls that lurk here I can only say - go get a life!

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