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Thread: high head?..

  1. #27
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    Jul 2004
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    West TN
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    983
    Does raising the condensing unit with a water hose help?

    I'm picturing a condensing unit dangling out of a tree hanging from the hose. Muahaha j/k
    Extend to others the grace that God has given you.

  2. #28
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    Nov 2001
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    east kansas
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    8,038
    As said earlier make sure the blade is in the right position in the orfice. Also new motor, was the blade changed? What about the pitch and proper rotation. Meaning was the original spun one direction and the new spins the other. I don't know if it would make a difference, except the cabnet may be designed for the air to enter one certain direction.

  3. #29
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    Feb 2004
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    southern illinois
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    didn't look like blade had been changed....

  4. #30
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    Dec 2002
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    Houston,Tx.
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    16,121
    Originally posted by beenthere
    Some one may have miss matched it, and just kept adding gas till they got a decent suction pressure. Which means it has to have a high head pressure to force enough refrigerant through the cap tube to keep from freezing the coil.
    Glad someone got it, that is exactly what I was talking about that would cause a higher head, If you have a larger condenser on a smaller evaporator "YOU WILL" have a lower suction been there done that many times in Houston the humidity capital of the world,and to compensate for the lower suction pressure to keep coil from freezing you will have to pump it up "or increase fan speed" more, thus increasing the head pressure. I have personally seen this hundreds of times, now rather it will effect the performance of the unit by stacking up the liquid or how high the head will get depends on the efficiency of the condenser one that is 15 years old I would say on a 98 degree day "You Will" see a head higher than normal. With the heat and humidity combo we get regularly in Houston 100 degree days with 100% humidity your smaller evap. on a larger condenser will not perform like a matched system if that were true the mfg. would save millions and just provide smaller evaps. to go with there condensers.
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  5. #31
    Join Date
    Jun 2004
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    247
    Originally posted by beenthere
    Some one may have miss matched it, and just kept adding gas till they got a decent suction pressure. Which means it has to have a high head pressure to force enough refrigerant through the cap tube to keep from freezing the coil.
    Would using a TXV sized to the condenser tonnage prevent this situation from happening?

  6. #32
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    Nov 2001
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    east kansas
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    The refrigerant may not flash at the right spot in the coil.

  7. #33
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    Mar 2005
    Location
    Suppy NC
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    4,516
    txv can not be added to a cap coil. cap tubes are you meater. you will have to change the coil and size it to the condenser.

  8. #34
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    Jan 2004
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    PA
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    68,753
    Yea, the txv would be what you need to use, also you would need to move the air for the CU size, and not the evap coil.


    Do a search for airman1, i believe, and you'll see what he does for humidity control.
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  9. #35
    Join Date
    Feb 2005
    Location
    Dothan, Al
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    3,453
    The compressor itself could be adding the extra 'heat' which raises the head pressure. Have seen this a number of times on older equipment. Especially Luxaires.

  10. #36
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    Feb 2004
    Location
    southern illinois
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    compressor is in compartment separate from condenser and fan...in this case.

  11. #37
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    Feb 2004
    Location
    southern illinois
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    think i'm just gonna suggest a cleaning and stop there...i've done everything i can to keep this thing going for him...even after having check in my hand and having equipment delivered for new install cause they thought they had leak....i figured it was plugged evaporator coil after i'd seen it changing out furnace....cause they said they had to have it gassed last year and i recovered a bunch out of old one after that....guess all of it was dirty???ooppss....well we will be in 60's here this week so i'll give him a ring and see what he wants to do,....his place is good haul from the house and i got another one to do about 35 miles from there....i 'll just make a 150 mile circle that day!...gonna try not to get no speeding tickets this time..last one was a little stiff on pocket book.

  12. #38
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    Feb 2004
    Location
    southern illinois
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    bad thing about it is these are kind of like startups from winter furnace work,new installs,etc.

  13. #39
    Join Date
    Apr 2003
    Location
    the Great Pacific Northwest
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    607
    Originally posted by mrbillpro
    Originally posted by beenthere
    Some one may have miss matched it, and just kept adding gas till they got a decent suction pressure. Which means it has to have a high head pressure to force enough refrigerant through the cap tube to keep from freezing the coil.
    Glad someone got it, that is exactly what I was talking about that would cause a higher head, If you have a larger condenser on a smaller evaporator "YOU WILL" have a lower suction been there done that many times in Houston the humidity capital of the world,and to compensate for the lower suction pressure to keep coil from freezing you will have to pump it up "or increase fan speed" more, thus increasing the head pressure. I have personally seen this hundreds of times, now rather it will effect the performance of the unit by stacking up the liquid or how high the head will get depends on the efficiency of the condenser one that is 15 years old I would say on a 98 degree day "You Will" see a head higher than normal. With the heat and humidity combo we get regularly in Houston 100 degree days with 100% humidity your smaller evap. on a larger condenser will not perform like a matched system if that were true the mfg. would save millions and just provide smaller evaps. to go with there condensers.
    I agree however the point I was making was that a smaller metering device would not cause high head it would cause low head and suction in and of itself. Overcharging to bring up the suction is simply stacking liquid in the condenser which raises head pressure causing the fixed metering device to feed more ref. A clear understanding of the ref. cycle allows for quick and accurate diagnosis of a problem, in this sernario checking subcooling would show overcharge (high subcooling, low approach perhaps 10 degrees or less) or dirty condenser (normal to low subcooling, with high approach)

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