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  1. #1
    Join Date
    Jul 2007
    Location
    Conroe, Texas
    Posts
    7

    Question High Superheat, Normal Subcooling

    I'm working on my own split a/c system and can't get the charge right so the unit will cool. It is a Goodman 4 Ton system with a fixed orifice. The inside and outside coils are both clean and I have good air flow. Since I had high superheat, I added R22 and the suction and head pressure go up, but I'm not even close on the charts. I'm already at 350 head, so I didn't want to add any more freon. Looking at the numbers below, would this mean that the compressor and condensor are fine, but the evaporator is starving for refrigerant due to a clogged orifice? The unit is 8 years old.

    Indoor temp= 81, RH=68
    Outdoor temp=93
    Suction press=65 (should be 38F), Actual suction temp=81F same as room.
    Superheat=81-38=43 High

    Discharge press=350, (should be 143F) Actual temp=130F
    Subcool=143-130=13 Normal

    Compressor amps rated at 22, pulling only 18

    Thanks,
    Paul

  2. #2
    Join Date
    Apr 2004
    Location
    Charlotte, NC
    Posts
    648

    Wow!

    The superheat isn't based on the indoor temperature, it is based on the pressure/temp of the evaporator, which is 38. That is low superheat. Stop charging the unit if you want to keep it. The fixed orifice doesn't control superheat, so whoever taught you how to do this stuff needs to be fired, and fast!
    The rating on the compressor is for reference and usually runs much lower than stated. The head pressure is high, and should only be around 275. You are going to destroy your unit.

  3. #3
    Join Date
    Jul 2007
    Location
    In an attic!
    Posts
    25
    Simply put theres too much refer

  4. #4
    Join Date
    Mar 2007
    Location
    Delaware
    Posts
    70

    Talking Back Away

    If you want to keep that unit working turn it off and call a PRO. You will thanks us later

  5. #5
    Join Date
    Jul 2007
    Location
    Conroe, Texas
    Posts
    7
    ckone180,
    I think you missinterpreted what I wrote.
    Superheat can be measure at the condensor if you also take into consideration the pressure drop from the evaporator to the condensor. I was saying that the actual temperature of the suction line at the condersor is 81 degrees which happens to be the same as the indoor temperature. The pressure of the suction line at the condensor is 65psig which on a R22 chart is 38 degrees.

    superheat=suction line temperature. -saturated suction temperature.

    I agee that the head pressure is high and that is why I did not add any more freon.

    Also for your information a manufacture rating of compressor amps is one way for an a/c tech to see how hard a compressor is working. It will normally be lower, but if you come accross one that is higher, you should not overlook it as just something the manufacture puts on a label. It's there for you to check and use it as a tool.

    Thanks,
    Paul

  6. #6
    Join Date
    Jul 2007
    Location
    Conroe, Texas
    Posts
    7
    By the way, I probably should have mention it in my first post. I am an ex a/c contractor with a state license. I didn't work for somebody else, I took the exam and own the license. I am also a licensed master electrican in all 50 states.I gave up my business and just take care of the 3 a/c systems in my home.

    Thanks,
    Paul

  7. #7
    Join Date
    Apr 2002
    Posts
    11,808
    never mind
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  8. #8
    Join Date
    Jul 2007
    Location
    In an attic!
    Posts
    25
    Quote Originally Posted by pmc181 View Post
    I gave up my business and just take care of the 3 a/c systems in my home.
    How much are you making doing that?
    All funnies aside, that is a high load and you mentioned possible restriction. Can you easily look at the evaporator? If so check the distributor tubes going in to the evap. checking for even flow of refer. across evap. thus indicating if you have a restriction.

  9. #9
    Join Date
    Apr 2004
    Location
    Charlotte, NC
    Posts
    648
    I appreciate the explanation on the superheat, I really thought you were refering to the indoor temperature. High superheat is right when you have a heavy load, but that doesn't reflect the normal subcooling at such a high head pressure. Filter-Drier, if you have one, may be clogged. Condensor may be dirty. Congrats on your license, I don't know what state you are in, but some states have a silly test. This type of issue appears to me as someone with a little experience could have fixed. Air flow, filters, cleanliness all affect the system, and could be giving you your problem. Think simple. Also, the ratings are the maximum it should operate at, take for example an AEA4440YXA, labeled at around 9amps, but different applications could result in 5-6 amp readings. That is a 40% difference.
    "Fighting Ignorance since 1973 (It’s taking longer than we thought)." The Straight Dope.

  10. #10
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    Quote Originally Posted by pmc181 View Post
    By the way, I probably should have mention it in my first post. I am an ex a/c contractor with a state license. I didn't work for somebody else, I took the exam and own the license. I am also a licensed master electrican in all 50 states.I gave up my business and just take care of the 3 a/c systems in my home.

    Thanks,
    Paul

    Total BS. If you ever had any type of a/c license and don't know what your problem is here, you dis-serviced anyone's system you put a wrench to. Very basic problem...like an electrician that can't figure out a breaker is tripped. If you were licensed, your state's licensing procedure stinks. JMO.
    If everything was always done "by the book"....the book would never change.

  11. #11
    Join Date
    Sep 2006
    Location
    Winter Springs, Fl
    Posts
    1,755
    yeah I think he needs to check the piston for the right size. low suction, high SH, high head, high to normal SC spells underfeeding metering device to me. the coil is starved like a mofo ( and overcharged to boot ).

    Better call a pro before you nuke the windings in the pump PMC. sorry man but you have the distinct stench of a DIY. If you were a A/C contractor at one time you should be able to determine the problem with your manifold and a pipe clamp probe and a little bit of gut talking to ya, without having to post it here. Why don't you email the guys at the website you bought it from. maybe they can help ya.
    If you can't learn to do something well, learn to enjoy doing it poorly.

    The HVAC-Talk Educational Forums is the best place on the net for your HVAC/R info!!!

    VETO PRO PAC - The Official Tool Bag of HVAC-Talk.com

  12. #12
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,846
    Quote Originally Posted by Maximus3 View Post
    Simply put theres too much refer.
    Can you have to much refer?

    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  13. #13
    Join Date
    Sep 2006
    Location
    Winter Springs, Fl
    Posts
    1,755
    Quote Originally Posted by mrbillpro View Post
    Can you have to much refer?

    NOw were talkin'
    If you can't learn to do something well, learn to enjoy doing it poorly.

    The HVAC-Talk Educational Forums is the best place on the net for your HVAC/R info!!!

    VETO PRO PAC - The Official Tool Bag of HVAC-Talk.com

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