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  1. #1
    Join Date
    Jun 2005
    Posts
    42
    About 2 months ago, I had the following installed:

    Lennox condensing unit (HSXA19-060) 5 ton, 2-stage scroll compressor
    Lennox matching evaporator coil (CX34-50/60C) with factory installed TXV
    Lennox 2-stage furnace (G60UHV-60C-110) (high blower fan speed at factory default of 1985 cfm).

    This post is a follow-up to a post from 7/9/05.

    After the system was installed, the technician charged the system using outdoor temperature and pressure gauges. It turns out that Lennox’s charging procedure is the approach method. To summarize the method, it says to record the outdoor ambient temperature using a digital thermometer. Then attach the high pressure gauge set and operate unit to allow pressures to stabilize. To charge, use the same digital thermometer to check the liquid line temperature that was used to measure the ambient temperature. About 2 weeks after the company had charged the system, I did the approach method (without any gauges) and found that I only measured a delta T of 3-4 degrees F. The Lennox literature shows that the system should have a delta T of 10 + or - 1 degree F. I contacted the company with my concerns.

    Last Friday, my installing company’s service manager came out with a technical rep. They measured the delta T at 1.5 degree F. The technical rep confirmed that the system was overcharged. However, my company was not able to adjust the charge that day. I have not heard from the company about when they are coming back so I am going to call them again. At this point, the system has been overcharged for approximately 6 weeks. It’s been very hot where I live and the system runs on high stage a lot of the afternoon.

    I wanted to see if anyone could tell me what kind of damage could be caused by an overcharge of refrigerant to a 2-stage scroll compressor or an evaporator coil. I am concerned since this is new equipment. It is Lennox's top of the line equipment and costs a lot of money. I’m sorry but I don’t know how much it is overcharged yet. The only info I have right now is the delta T being 1.5 degrees instead of the specified 10 degrees. Also, when they adjust the charge, will they be able to tell me how much it is overcharged? Thanks for any help you can give me. I really appreciate all of the information on this forum.



  2. #2
    Join Date
    Feb 2005
    Posts
    40
    because the scroll compressor doesn't have any reed valves in them, it makes for a much better compressor. They can take a floodback situtation much better than the old reciporcating compressor. Plus, with the TXV it will regulate the refrigerant according to the heatload that is put upon the evaporator coil. This will prevent floodbacks to the compressor. I don't think you have much of anything to worry about.

  3. #3
    Join Date
    Mar 2002
    Location
    Richmond, Virginia
    Posts
    4,264
    They can tell you how much overcharged the system is if the recovery cylinder is sitting on digital scales as the refrigerant is removed.

    The fact that the evaporator coil is equipped with a txv will likely prevent floodback of liquid refrigerant to the compressor. However, for other reasons the system charge should be corrected.

    Nice system by the way.
    There is nothing more frightful than ignorance in action....Mark Twain

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