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Thread: System charging

  1. #1

    System charging

    Finally got some time to do some PM on my system for the summer. Washed/cleaned outside coil, checked inside coil, replaced air filter, and checked insulation on the suction tube.

    I just checked pressures and temps after letting the unit run for a good 10-15minutes, and here is what I have:

    liquid pressure: 150psi
    liquid line temp (at outside unit): 84degrees
    Suction pressure: 60psi (varied between 58-60)


    Now, the system at my house is a bit of a frankenstien. The outdoor unit is a Frigidaire FT3BD, the air handler is a frigidaire B5BM. None of Nordyne's literature mentions these two together, and the FT3BD charging graphs do not have any data for an indoor TXV. So what I did was take the charging graph from their FT5BD literature (which uses the same ZRK3 compressor), which does have a graph for TXV charging, and used that. I attached the graph.

    It appears the system is about 25psi low. I also measured temperatures at the air inlet and outlet of the air handler. Incoming is 75degrees and out is 64 degrees. System is cooling fine, but I wanted to make sure it is working at peak efficiency.

    Just wanted to get some opinions here before I call to get it charged!
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  2. #2
    Join Date
    Jul 2001
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    VA
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    Not much to make an opinion about.....

    we still don't have nearly enough info.

    You are aware it is likely low, but you're main concern should be getting the leak fixed.

    When it's fixed the tech should know how to tune it.
    ___________________________________________


  3. #3
    Join Date
    Feb 2008
    Location
    Western NC
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    another engineer trying to do HVAC......


    its sad that those that make a decent living must find every possible way to save a penny.


    25 psi low huh, yeah thats it. Now convert that to pounds at barometric temp, add your sea level, divide by the current temp and add the amout of rain (in centimeters in the last 24 hours) and you will know how many metric tons of "freon to add.


    Get a real tech out to diagnose the problem. And to fix it properly.
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  4. #4
    I actually don't believe it has a leak..

    The system was installed in the summer, and was working very well. When the time came, I had the installer back out in the winter to verify heating operation. They said it was overcharged, and took some refrigerant out. According to them, it was due to the outdoor unit having a piston and the indoor unit having a TXV.

    Anyways, I think they took too much out, causing it to be a little low during cooling operation. Trick is finding that happy middle between cooling and heating operation.

    What other info would you like about the system? Outside unit is 2.5ton, air handler is a 3ton. R-22 system.

  5. #5
    Join Date
    Feb 2008
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    Western NC
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    ok.,....

    if you need to be put on a "freon" agreement. Then you either have a system mismatch or you have an improperly sized lineset.

    Thats pretty easy.


    next, you need to have the techs doing the maintainence. This is not a DIY site and we cannot help you as a DIYer. Not to mention, you technically just voided your warranty when you began taking pressure readings. And EPA regulations.(unless you have EPA cert.)
    I fully support the military and the War on Terrorism.


    If you don't know, then don't do. If you don't know and still do, then be prepared to pay someone else a lot to undo what you did and then do it right.

    If you do know, then do. But do it right. Otherwise, you may not be doing it long.

  6. #6
    Quote Originally Posted by iraqveteran View Post
    another engineer trying to do HVAC......


    its sad that those that make a decent living must find every possible way to save a penny.


    25 psi low huh, yeah thats it. Now convert that to pounds at barometric temp, add your sea level, divide by the current temp and add the amout of rain (in centimeters in the last 24 hours) and you will know how many metric tons of "freon to add.


    Get a real tech out to diagnose the problem. And to fix it properly.
    A real tech huh? Like the 8 companies I called to come out and do the initial estimate, and all but 2 wouldn't do or didn't know what a manual-J was? Or like the company that just installed my neighbors unit and vented the entire system to the atmosphere?

    Thanks for adding meaningful information to the thread.. I didn't know the title of this forum was "You're not allowed to know, now go away".

  7. #7
    Quote Originally Posted by iraqveteran View Post
    ok.,....

    if you need to be put on a "freon" agreement. Then you either have a system mismatch or you have an improperly sized lineset.

    Thats pretty easy.


    next, you need to have the techs doing the maintainence. This is not a DIY site and we cannot help you as a DIYer. Not to mention, you technically just voided your warranty when you began taking pressure readings. And EPA regulations.(unless you have EPA cert.)
    I spoke with a tech at Nordyne about the units that are installed, and he insisted that they are a compatible match.

    I do have a 608 universal cert..

  8. #8
    Join Date
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    You may have a seasonal charge imbalance that needs to be corrected, for that.....you do indeed need a real tech.

    Are you EPA certified?
    ___________________________________________


  9. #9
    Join Date
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    Quote Originally Posted by mdengineer View Post

    I do have a 608 universal cert..
    Ok
    ___________________________________________


  10. #10
    Quote Originally Posted by DPSwitch View Post
    You may have a seasonal charge imbalance that needs to be corrected, for that.....you do indeed need a real tech.

    Are you EPA certified?
    I was thinking along the same lines... Thanks. Had I known as much as I do now I probably would have requested models that were matched as per the documentation. Hindsight and all that.


    Also wanted to appologize for my previous post. I am attempting to get as much information as I can before I consult an outside person. In my real line of work, I prefer the person I am working with is knowledgable about the problem we are trying to solve. It has been my experience that most of the people I invite over to inspect my system do not wish to discuss the details and instead only offer a price. I am not out to second guess anyone, but do like to be informed more than just "its fixed, gimme $300".

    I decided to get my cert so that I could check my system myself, as well as my parents. I intend to keep a log of my readings to help troubleshoot future issues. Sorry if I came across as someone who decided to buy a goodman online and install it himself .

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    You might have a seasonal charge imbalance. But you shouldn't if its a matched system as Nordyne said.

    But, look at the fan data plate for that blower. Those are weak blowers, usually only rated at .4" TESP. Meaning you might have very low air flow. Which could make it seem over charged in the winter, and under charged in the summer.
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  12. #12
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    Very good points
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  13. #13
    Join Date
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    VA
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    Oh md.

    If you are going to check those pressures yourself. Do yourself a favor and don't use standard charging hoses.

    Get yourself some little stubby gauge connectors or the little short 5" or 6" hoses.

    Every time you put the gauges on you are taking refrigerant out of the system, especially on your liquid line. Lose a hose full of liquid on several checks and it adds up.

    Since you arent adding or taking away, you dont need to use a manifold.
    ___________________________________________


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