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  1. #1
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    low sub cooling with replaced condenser coil

    Replaced with new condenser coil for a packaged unit. R-22 txv system. After commissioning, I checked its operation parameters and found sub cooling is not enough. it is below 2F. local manufacture says that the coil is the copy past of the old unit. Same physical measurement of the old condenser coil. What would be the errors of the new coil? The discharge pressure is maximum, condenser split is 30F, so cannot charge more refrigerant. and the condenser fan is ok. Any comments really appreciated. thanks

  2. #2
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    The only things i can think of are a poorly made condensor, non condensables in the condensor or incorect condensor.

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  3. #3
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    Does it have the same number of rows of tubes?
    Does it look more restrictive to air flow?
    Did you preform a good leak check and evacuation?

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  4. #4
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    Thread Starter
    the commissioning process was done by the same coil manufacture. i was not witnessed the evacuation process. and you are correct, i have to recheck whether the new coil is matching with the old. i was told by coil maker that it is same copy past of old coil.

  5. #5
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    there is no air flow restriction. here in dubai is common method is that the coil manufacture will not provide more info that the total volume of coil, heat capacity of condenser...etc. they just replaced a coil. when i talk their engineer about subcooling,he told me that howto check it!!

  6. #6
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    Interesting. Sounds like you need to do some checking. I am interested to hear what you find.

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  7. #7
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    Quote Originally Posted by moideen View Post
    The discharge pressure is maximum,
    LOL, What does this mean? Are you saying the pressure is almost about to trip the High Pressure Safety? Or are you saying the compressor is running full rated load according to its name plate? Or do you just feel like it is as high as you want it to go because on a scale of 1 to 10 you feel like you’ve reached 11?





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  8. #8
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    Sounds like a piping design issue with the coil.

    I would weigh in factory charge, and let it go. If you have a solid column or liquid at the metering device, you should be fine.

  9. #9
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    One of the ways subcooling can be low is if an unusually large liquid line filter drier was installed, which is acting as a receiver and you're measuring the subcooling before that filter dryer.
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  10. #10
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    Quote Originally Posted by thatguy View Post
    LOL, What does this mean? Are you saying the pressure is almost about to trip the High Pressure Safety? Or are you saying the compressor is running full rated load according to its name plate? Or do you just feel like it is as high as you want it to go because on a scale of 1 to 10 you feel like you’ve reached 11?





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    the condenser split(TD) will tell the maximum possible discharge pressure. for air conditioning, the TD will be 20 to 30F.

  11. #11
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    Quote Originally Posted by timebuilder View Post
    One of the ways subcooling can be low is if an unusually large liquid line filter drier was installed, which is acting as a receiver and you're measuring the subcooling before that filter dryer.
    no, the filter drier is proper.

  12. #12
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    Quote Originally Posted by 71CHOPS View Post
    Sounds like a piping design issue with the coil.

    I would weigh in factory charge, and let it go. If you have a solid column or liquid at the metering device, you should be fine.
    yes, the indicator of the solid column is achieving 5 to 8k(9 to 14F) subcooling

  13. #13
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    low sub cooling with replaced condenser coil

    Quote Originally Posted by moideen View Post
    the condenser split(TD) will tell the maximum possible discharge pressure. for air conditioning, the TD will be 20 to 30F.
    I was laughing because you haven’t posted any actual numbers for us to see except for the split. It didn’t give us much to work with. The quality of help you get is directly related to the quality of information you give us. Pressures (If you happened to have had your gauges on at the time), temperatures, electrical readings, model numbers, any of that (the more the better) will help is help you better. I hope you aren’t offended when I second guess you when you say it’s good without providing the results you got when you came to that conclusion. Our job is to question what the last person did when we go to troubleshoot a piece of equipment. If there is a problem unit we need to go with a fresh set of eyes. Weather it be our brother, our coworker, or another company, we need to use the information acquired by them with caution because if we go by what they tell us then we may miss the same thing that they missed.

    The temperature split in a condenser will vary depending on the efficiency rating of the unit. Low efficient (low SEER) units can typically have around a 30 degree split where as the newer higher efficiency units with their larger coils may only have 10 degrees split.

    Assuming that a 30 degree split is correct for that system then let’s look at condenser airflow (you mentioned it was good but because you didn’t specify how you determined that). Are the fan amps correct, capacitor the correct size and within it’s rated tolerance, bearings spin freely and smooth? Proper size prop fan installed, and spinning the correct direction? Proper condenser fan blade height within the orifice, and the proper pitch fan blade? Proper airflow around the unit to reject the heat?

    Have you checked to see if the TXV is flooding back? What is the split on the indoor coil?

    I may have miss understood one of you’re later posts. You mentioned in the first post that you had 2 Deg F subcooling but in your last post you mentioned that you had 9 or 14 Deg at the metering device. Can you clarify that? I’m guessing you meant the name plate requests 9-14 Deg, but I hate guessing.


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