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  1. #14
    Join Date
    Sep 2005
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    Atlanta GA area
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    Quote Originally Posted by Florida Joy View Post
    It's been my understanding that the accumulator (comes standard with heat pumps) protects the compressor from such "starvation". True or not?

    Also, what constitutes a "large pocket" in the lineset? As you can see in the pix I posted, the current lineset makes a pretty sharp U turn from where it exits the foundation to reach the condenser.
    Not all HP's have an accumulator... some have a charge compensator... different animal that does a different thing.

    A large pocket would be a section of lineset which is low for several feet and goes back up. A simple U bend is not significant.
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  2. #15
    Join Date
    Aug 2012
    Location
    Florida Space Coast
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    503
    Quote Originally Posted by ga-hvac-tech View Post
    Not all HP's have an accumulator... some have a charge compensator... different animal that does a different thing.
    Didn't know that. HP's I'm considering have an accumulator.

    Quote Originally Posted by ga-hvac-tech View Post
    A large pocket would be a section of lineset which is low for several feet and goes back up. A simple U bend is not significant.
    If it only "goes back up" 12 inches or so, would that be considered a "large pocket"? I've been reading about p-traps in linesets to counteract oil pooling... seems they're only recommended when the lineset "goes up" 15 feet or more.

  3. #16
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,317
    Quote Originally Posted by Florida Joy View Post
    It's been my understanding that the accumulator (comes standard with heat pumps) protects the compressor from such "starvation". True or not?

    Also, what constitutes a "large pocket" in the lineset? As you can see in the pix I posted, the current lineset makes a pretty sharp U turn from where it exits the foundation to reach the condenser.
    If oil is hanging up in the suction line upstream from an accumulator, the accumulator itself can't do what it should. Accumulators do two things...they reduce the risk of liquid refrigerant entering the compressor when the heat pump reversing valve shifts (during defrost operations) and they promote good oil return to the compressor when the system is in heat mode (due to lower suction velocities). The risk of oil hanging up in a suction line, with heat pumps, will be during cooling mode operation. Line sets that are underground can pose this risk, since, depending on soil temperature, can cool the suction gas to where velocity slows and oil precipitates out of the suction gas, onto the walls of the pipe.

    However, if you already have a lineset under the slab, and it's in a sleeve vs. in contact with soil (such as was the case with my parent's house, who suffered multiple compressor failures as a result), and all you want to do is tie into where the line set emerges into the existing condenser's location, and extend further over several feet, that may be okay...it might also create an oil return problem that was not there before, due to added line length and slowed velocities. Total line length would need to be considered for this proposed extension.
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    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


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  4. #17
    Join Date
    Aug 2012
    Location
    Florida Space Coast
    Posts
    503
    Quote Originally Posted by Shophound View Post
    However, if you already have a lineset under the slab, and it's in a sleeve vs. in contact with soil (such as was the case with my parent's house, who suffered multiple compressor failures as a result), and all you want to do is tie into where the line set emerges into the existing condenser's location, and extend further over several feet, that may be okay...it might also create an oil return problem that was not there before, due to added line length and slowed velocities. Total line length would need to be considered for this proposed extension.
    Existing lineset is, at most, 25' total between ahu connection in the laundry room and condenser connection outside. Extension would add approx. 12 - 15' of horizontal lineset for a total, at most, of 40'.

    FYI, due to the configuration of the attic "around" the atrium, running the lineset up through the attic and then down the exterior wall would likely involve a lineset of at least 60'.

  5. #18
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    I'd only run the refrigerant lines under ground if they were in an absolutely water tight PVC chase, and I'd use the smallest allowable vapor line size for the application to keep the refrigerant velocity high for oil return.

    Quote Originally Posted by second opinion View Post
    I believe you are on 2005 NEC, take a look at 110.34 A Spaces About Electrical Equipment.
    We all understand your point, but you may want to cite the correct code reference.

    The one you cited is for high voltage equipment, 600v+.
    If more government is the answer, then it's a really stupid question.

  6. #19
    Join Date
    Aug 2012
    Location
    Florida Space Coast
    Posts
    503
    Quote Originally Posted by Florida Joy View Post
    Existing lineset is, at most, 25' total between ahu connection in the laundry room and condenser connection outside. Extension would add approx. 12 - 15' of horizontal lineset for a total, at most, of 40'.

    FYI, due to the configuration of the attic "around" the atrium, running the lineset up through the attic and then down the exterior wall would likely involve a lineset of at least 60'.
    Quote Originally Posted by mark beiser View Post
    I'd only run the refrigerant lines under ground if they were in an absolutely water tight PVC chase, and I'd use the smallest allowable vapor line size for the application to keep the refrigerant velocity high for oil return.
    I've ruled out the underground option based on reported problems in The Villages community in Central Florida where the builder buried the refrigerant lines. Now my choices are:

    (1) extend the lineset to approximately 60' by running it up from the ahu, through the attic, around the perimeter of the atrium, then down the exterior wall inside a vertical chase to the new location, or

    (2) use the existing PVC chase under the foundation to get the lineset outside where it is currently, then extend the insulated lineset horizontally through a vented chase along the exterior atrium wall (no more than 12 inches above the ground) to the new location, for a total run of no more than 40'. Snow is not an issue (lol) and at 12" above ground, water is not an issue either... I have excellent drainage... proven during TS Faye in 2008.

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