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Thread: line sizes

  1. #1
    Join Date
    Aug 2004
    Location
    Texas
    Posts
    88

    Question

    I am working for an apartment complex. Just recently started. They are losing compressors at the rate of about two a week. Less than 5 years old. They have been installing 2 ton Goodmans without changing out the evaporator coils. The units don't seem to cool very well. Temp diff. is only 11 to maybe 15 degrees across evap. coil. 2 things got me wondering... The evap. coils are 2 and half....and the liquid line is 5/16. From the original installs. The goodman condensor specs call for 3/8. Could this be the reason they aren't getting any efficiency?

  2. #2
    Join Date
    Oct 2002
    Posts
    970
    Engineers would probably say yes, but between me and you, it wouldn't make a whole lot of difference unless the condensing unit is a quarter mile away..
    I work with the Chiller Whisperer...

  3. #3
    Join Date
    Jun 2004
    Location
    Richmond Virginia
    Posts
    1,078
    The line size difference you are speaking of won't matter a great deal on a short line run. If the line set is over 30 feet and has a significant rise it could certainly cause problems. What type of metering device do those old coils have? Most old ones would have been equipped with cap tubes and that old condenser pushed a lot of head pressure to push through those tubes. What most apartment places will do is put in that Goodman, and dump about five extra pounds in it to drive up the head pressure and raise the suction eventually to a level above freezing and call it done. Does that sound about right?

    By the way, that 10 SEER condensing unit is knocked down to an 8 if you're lucky when doing this.

  4. #4
    Join Date
    Aug 2004
    Location
    Texas
    Posts
    88
    thanks seaboard, the lines are about 30 feet more or less. These are slant coils, with cap.tubes. I have tried to charge according to the charging directions that come with the units. Taking dry air return temp. and ambient..etc, etc. And have the charge set when I reach the recommended superheat. The best temp. I can get coming out of the supply right above the evaporator is 62-63. Now when I install units that have the "A" coil I do everything the same way. And temp. from evap. is around 52-54. About a 20 degree temp./diff. from return air.
    I got out of the a/c business in 84' and just really started getting back into it. Things have changed a little. LIke I had to go get the epa certification. Anyway maybe the slant coils just don't put out as well. I don't know.

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