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Thread: Superheat

  1. #1
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    Superheat

    Have large residential apartment complex, units have fixed orifice, will be charging by superheat but cannot gain access to suction line leaving evaporators. What should the superheat reading be at compressor suction line?

  2. #2
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    That's goona vary too much depening on where each lineset runs and how long.

  3. #3
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    I always check my superheat at the outdoor unit near the suction service valve and I just use a standard superheat calculator to make that determination. I wouldn't think there would be enough difference between checking at the Evaporator outlet and the outside unit to matter unless you have a long run of lineset that is in direct sunlight.

    SB is it better in your opinion to check SH at the indoor coil?
    Last edited by Rob_in_WV; 03-19-2013 at 08:04 PM. Reason: added a question to end.

  4. #4
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    Well I do always check it at evap if I'm going to add any. Especially if its a txv.

    Buried linesets/ long lines in attic can pick up 10deg pretty easily in my experience.

  5. #5
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    I would check the manufacture charging specs. For superheat most of the time they want you to take suction line temp at compressor or at the suction line entering at condensing unit.

  6. #6
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    Quote Originally Posted by SBKold View Post
    Well I do always check it at evap if I'm going to add any. Especially if its a txv.

    Buried linesets/ long lines in attic can pick up 10deg pretty easily in my experience.
    What is this refrigeration 101?
    He said he had units with a fixed orifice I:E a piston. In that case you take superheat 4-6" before the suction line service valve on the condensing unit and if it's a TXV then you don't take superheat readings, you take subcool readings.
    buried and long linesets should be TXV only. again subcool readings, not superheat

  7. #7
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    If they will not let you access the evaporator I would just do my best and not worry about it.

  8. #8
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    Quote Originally Posted by superfittertech View Post
    What is this refrigeration 101?
    He said he had units with a fixed orifice I:E a piston. In that case you take superheat 4-6" before the suction line service valve on the condensing unit and if it's a TXV then you don't take superheat readings, you take subcool readings.
    buried and long linesets should be TXV only. again subcool readings, not superheat
    I always verify both with a TXV so that I know the valve is metering correctly.

  9. #9
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    Quote Originally Posted by Rob_in_WV View Post
    I always verify both with a TXV so that I know the valve is metering correctly.
    Either way you still take your readings @ the condensing unit

  10. #10
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    Quote Originally Posted by atlantis View Post
    Have large residential apartment complex, units have fixed orifice, will be charging by superheat but cannot gain access to suction line leaving evaporators. What should the superheat reading be at compressor suction line?
    need to know the outside DB and evap inlet WB to get tareget SH, plus ensure proper airflow to know if your measured SH is even correct.

    Quote Originally Posted by Rob_in_WV View Post
    I always verify both with a TXV so that I know the valve is metering correctly.
    we have a winner!

    Quote Originally Posted by superfittertech View Post
    Either way you still take your readings @ the condensing unit
    yes, but if you cannot get inside whats the point? ( see above)
    my boss thinks its possible to repeal the laws of physics

  11. #11
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    Quote Originally Posted by superfittertech View Post
    What is this refrigeration 101?
    In that case you take superheat 4-6" before the suction line service valve on the condensing unit
    Disagree with ya there
    some places with poor armorflex and/or 50' lineset in a attic that is 130 F
    i do check on the outside and if it looks normal then i may not check coming out of the IDC. But if the SH seems high i prefer to go check it coming out of the coil so i can see what is going on with the system. JMO

  12. #12
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    *We are the Champions starts Playing loudly in the background.*

    CH4MAN what did I win?

  13. #13
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    Quote Originally Posted by klee7013 View Post
    Disagree with ya there
    some places with poor armorflex and/or 50' lineset in a attic that is 130 F
    i do check on the outside and if it looks normal then i may not check coming out of the IDC. But if the SH seems high i prefer to go check it coming out of the coil so i can see what is going on with the system. JMO
    So you have schrader fittings at the IDC of these units. Or you just guess what the pressure is at the IDC.
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