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  1. #1
    Join Date
    Jun 2005
    Location
    Louisville, KY
    Posts
    389

    Question

    I looked at a 10 ton (2-5 ton comps.tandem) YORK commercial split system today. The sight glass showed significant vapor circulating through the liquid line. I added refrigerant until the sight was full. It took a significant amount. 20lbs. The system still did not seem to operate at full cooling capacity. After the system had stabilized I took note of the pressures. The head was running around 250 while the suction was running around 110. It was approximately 90 degrees outside ambient and 75 degrees return air (indoor temperature greatly due to 20 ton system functioning properly in attached adjacent conditioned space). My only logical conclusion is that the TXV is not metering properly and allowing too much refrigerant to flow into the evap. This to me explains why so much vapor was present in sight glass on such a new system (excluding the possibility of a leak) thus greatly decreasing cooling capacity and showing disproportional pressure readings on guages. I have not looked at the TXV to examine because of it being located in a very difficult to access AHU hanging from a 20 foot high ceiling. I'm hoping to have some additional input from this MB so as to have a solid plan of action when I do make the effort necessary to access the TXV. Have any of you had this experience and/or have any ideas about what these symptoms indicate? Your input is greatly appreciated.

  2. #2
    Senior Tech Guest
    One things for sure...it's overcharged.

  3. #3
    Join Date
    Jun 2005
    Location
    Louisville, KY
    Posts
    389
    What makes you say its over charged? The head presure is not high enough relevant to outdoor ambient and high suction to indicate overcharge.

  4. #4
    Join Date
    Apr 2003
    Location
    south texas
    Posts
    412
    try a pump down on the compressor to check the valves in the compressor. what is the temp of the suction line and what is your subcooling temp?

  5. #5
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    If this is a new system it could be that someone forgot to clamp down the feeler bulbs from the TXVs. This would let them run wide open. I am assuming the cu is above the ahu.

    Some sort of a platform should be constructed so that you can service this unit. In order to properly diagnoise any TXV problem you must take superheat readings. What ever it takes you have to get to these valves. Make sure these blubs are TIGHT. Try to move the blubs on the pipe with all of your might. If you can then they are not tight enough.

  6. #6
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    If this is a new system it could be that someone forgot to clamp down the feeler bulbs from the TXVs. This would let them run wide open. I am assuming the cu is above the ahu.

    Some sort of a platform should be constructed so that you can service this unit. In order to properly diagnoise any TXV problem you must take superheat readings. What ever it takes you have to get to these valves. Make sure these blubs are TIGHT. Try to move the blubs on the pipe with all of your might. If you can then they are not tight enough.

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