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  1. #1
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    Suction Line Temp?

    In a typical overcharge for a residential split-system I understand the Discharge and Suction Pressures are higher than normal. The Superheat is low because of increased velocity, having less time to absorb heat from the heat load after leaving the latent heat zone. Subcooling is more than normal because there is more liquid in the condenser being exposed to ambient. Current draw in increased because the compressor is working harder to move more refrigerant.

    So, WHY IS THE SUCTION LINE COOLER THAN NORMAL? Is it not because of the velocity, and the fact that the gas has less time to be exposed to the heat load, which would raise it's temperature and increase the superheat?
    "It's what you do when you don't have to that makes the difference when it counts."

  2. #2
    Join Date
    Apr 2007
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    Why didn't you post this in the pro section?

  3. #3
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    Huh?

    I thought the entire site was for professionals.
    "It's what you do when you don't have to that makes the difference when it counts."

  4. #4
    Join Date
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    Atlanta(metro)
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    Quote Originally Posted by hungryjack View Post
    In a typical overcharge for a residential split-system I understand the Discharge and Suction Pressures are higher than normal. The Superheat is low because of increased velocity, having less time to absorb heat from the heat load after leaving the latent heat zone. Subcooling is more than normal because there is more liquid in the condenser being exposed to ambient. Current draw in increased because the compressor is working harder to move more refrigerant.

    So, WHY IS THE SUCTION LINE COOLER THAN NORMAL? Is it not because of the velocity, and the fact that the gas has less time to be exposed to the heat load, which would raise it's temperature and increase the superheat?
    In an overcharge the suction line is not cooler than normal as the superheat is low(due to flooding of evaporator coil ...only small portion refrigerant in coil going from liquid to vapor)

  5. #5
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    Jan 2008
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    Madison In.
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    Flooded.

  6. #6
    Join Date
    Jan 2004
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    Lancaster PA
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    Its because of the liquid coming back.


    To the OP.

    The "pro tech forum" is for technical questions.
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  7. #7
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    Atlanta(metro)
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    Quote Originally Posted by beenthere View Post
    Its because of the liquid coming back.


    To the OP.

    The "pro tech forum" is for technical questions.
    dont know about cooler than normal the temp will be equal to its equivalent pressure little to no superheat.

  8. #8
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    With higher than normal suction and discharge temps wouldn`t that mean higher than normal saturated suction temps so I am not sure how temp could be cooler "than normal"

  9. #9
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    Mar 2008
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    Atlanta(metro)
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    Quote Originally Posted by thegoodlistener View Post
    With higher than normal suction and discharge temps wouldn`t that mean higher than normal saturated suction temps so I am not sure how temp could be cooler "than normal"
    exactly

  10. #10
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    Aug 2003
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    Deja vu. I answered this exact OP in the Pro Tech section. Ain't gonna repeat myself here. I can see it's been covered well enough as is. Please remember the rules regarding multiple posts of same topic (not allowed).

  11. #11
    Join Date
    Jan 2004
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    Lancaster PA
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    Since SH is how much warmer then the ST, when you get liquid back it will get cooler to a certain point first. Then it will warm up.
    Depends on amount of overcharge.
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  12. #12
    Join Date
    May 2006
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    east central indiana
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    Lol, what's going on with this thread, now?

    WHY IS THE SUCTION LINE COOLER THAN NORMAL?
    Normal being...?
    Normally you have some superheat present. As you overcharge your superheat goes down, so does your line temperature. Eventually you'll get the superheat down to zero at which time you have a fairly solid stream of liquid refrigerant returning to the compressor, rather than superheated vapor.
    In regards to the P-T relationship which was mentioned about earlier, yes you will be seeing a higher pressure. But refrigerant does not normally return to the compressor at saturated temperature, hence the term "superheat". It will be returning to the compressor at saturated temperature + 20, or whatever amount of superheat you have.
    With an overcharge like this, then you will have saturated temperature + 0 returning to the compressor, it couldn't pick up enough heat to boil. So there's your "colder than normal" suction line. Whatever "normal" is.

    Or maybe you have a kink in your suction line
    This space for rent.

  13. #13
    Join Date
    Oct 2003
    Location
    Valdosta Ga
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    847
    Yes , but would the subcooling be higher with just the overcharge issue.

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