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  1. #1

    Return Plenum opening size. The installers are here now!

    I am having a 4 ton Trane XL16i/TAM7 installed right now. The installers built a long, about 4 feet, return plenum under the AH. It has two 14 inch flex ducts attached to it.The opening in the end of the return plenum is 9"x18" according to them. I saw it and thought it looked too small, expecially since all the estimates I got told me that my two 14 inch ducts were marginal. Is that large enough for a return duct to a 4 ton AH? Thanks for your advice

  2. #2
    Join Date
    Jan 2007
    Location
    Jacksonville,Fl
    Posts
    123
    No,
    It needs to be 14" X 18" at the trunk opening or larger, this will move 1600 cfm at .08 static, this is my recommendation without having equipment specs handy, but I doubt what you have will work with that duct size.

  3. #3
    Quote Originally Posted by Krzyd View Post
    No,
    It needs to be 14" X 18" at the trunk opening or larger, this will move 1600 cfm at .08 static, this is my recommendation without having equipment specs handy, but I doubt what you have will work with that duct size.
    I called the salesman and he called the installers. They added another plenum to the side of the plenum under the unit and tied my second 14 inch flex into that. I think I have enough return now. This is why I absolutly hate to hire anybody to do anything in my house. I should not need to tell a guy that has been installing AC for many years how to do his job. The saleman sounded like he knew what he was doing, but he is not here for the install. I hope they flushed the lines correctly. It took them about 3 tries before they got their solder job to hold pressure. It has been raining during the whole install. Vacuuming the lines now, but they have no vacuum gauge.

  4. #4
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    Quote Originally Posted by LineOfSight View Post
    I called the salesman and he called the installers. They added another plenum to the side of the plenum under the unit and tied my second 14 inch flex into that. I think I have enough return now. This is why I absolutly hate to hire anybody to do anything in my house. I should not need to tell a guy that has been installing AC for many years how to do his job. The saleman sounded like he knew what he was doing, but he is not here for the install. I hope they flushed the lines correctly. It took them about 3 tries before they got their solder job to hold pressure. It has been raining during the whole install. Vacuuming the lines now, but they have no vacuum gauge.
    Sounds like you took the low price lol

  5. #5
    Quote Originally Posted by Joehvac25 View Post
    Sounds like you took the low price lol
    Actually, no. I took the middle quote. I got 5 qoutes. An acquaintance of mine gave the lowest quote, but I was concerned about his professionalism.

  6. #6
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    Quote Originally Posted by LineOfSight View Post
    Actually, no. I took the middle quote. I got 5 qoutes. An acquaintance of mine gave the lowest quote, but I was concerned about his professionalism.
    That's great I love when people use there head not there wallet. Hopefully everything turns out ok, leaks happen , too much nitrogen can sometimes blow out soldier. Did they purge with nitro?

  7. #7
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,326
    Rain + trouble with brazing + no vacuum gauge = hmmm....hopefully the installer's warranty is longer than when his tailights leave your driveway for the final time.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  8. #8
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,837
    Evacuation without a micron gauge is not a proper evacuation. Leaks, moisture (rainy day and all) beg for a guarantee that the piping is clean and leak free as well as free of moisture. Moisture + heat + refrigerant = a recipe for acid = compressor burnout. I would not let them open the refrigerant lines without first having a micron gauge evacuation to verify system integrity and dryness.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  9. #9
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    3,131
    Quote Originally Posted by LineOfSight View Post
    I hope they flushed the lines correctly. It took them about 3 tries before they got their solder job to hold pressure. It has been raining during the whole install. Vacuuming the lines now, but they have no vacuum gauge.
    wow. on a new install, I will NOT open or weld lines when it's rainy weather...
    I hope they used several tanks of nitrogen/CO2... I STRONGLY recommend you refuse to allow them to open the lines to the system before they get the lines PRESSURE tested, and then PURE micron tested, to hold below 500Microns for 15 minutes!!! if not, you've still got moisture in the lines, and your system will need SEVERAL dryers to clean up...
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
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    The A/C repairman

  10. #10
    The install is done now. I tried to stop them from charging the units in the rain, but they said "no problem, it has a Schrader valve." Riiiight. Then they apparantly overcharged the one unit as they got a high pressure trip of the compressor. They stuck a hose from their manifold valve into a bucket of water and bled off a good amount of 410a freon into the air. Then, they sent a more knowledgeable guy out the following day to final check the install and the charges. He said it was still overcharged. He also "corrected" some of the wiring and dip switch settings that the "installers" got wrong. I had noticed that one of the stats had no wire connected to Y2.
    The humidity has been higher in here than normal. One of the reasons I bought the Variable Speed, Two Stage units was because it is supposed to remove humidity better. I think he has forgotten one important step in wiring these units correctly. The BK-R jumper in the TAM7 is still uncut. Y is wired to Y1 and Y2 is wired to Y2. I read that there used to be a problem with the XL16i using the BK terminal as part of it's normal wiring. I think Trane changed that sometime ago. Now I have R jumpered to U1 in the Stat and the other U1 in the stat is wired to BK in the TAM7. That should allow the humidistat in the Honeywell TH8321U1097 to control fan speed via the BK terminal when the humidity is higher than the humidity set point. However, if the BK-R jumper is NOT cut, then BK is powered all the time. BK needs to be unpowered to get the fan to go to low speed. Do I have this right? I asked the salesman about this yesterday and he said he thinks that the fan will run all the time if BK Jumper is cut. I have never read that anywhere. He says he is going to consult the manuals and call me next week. By the way, Comfort R/Enhanced Mode is enabled.

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