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  1. #14
    Join Date
    May 2003
    Posts
    77

    Wink

    As previously stated, this is common. Always trust your contractor.

  2. #15
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,923
    Originally posted by tulsatwisters
    In a normal residential heat cool split system there are four components to consider. The air handler, condensing unit, evaporator coil and metering device. The components used must be compatible with each other, but you have to take a couple of factors into account. The total BTUH capacity and the SEER rating. Considering airflow only, the air handlers manufactured are designed to move a set amount of air in the cooling and heating modes based on a set factor per ton of cooling and heating capacities. The condensing unit BTUH should be sized to match the CFM capacity of the air-handling device. Considering BTUH In residential heating and cooling, the condensing unit should match the evaporator coil and metering device. However, the calculation must take into account the SEER rating of the equipment used. Looking at various SEER ratings for the same BTUH condensing units, there are different volumes of refrigerant for each of the different SEER ratings being moved through the system. This volume of refrigerant must be taken into account in sizing the evaporator coil and metering device. As the SEER rating increases on the condensing unit being used, so does the volume of refrigerant being circulated through the system. In order to properly accommodate this increase in volume of refrigerant, the metering device would need to be sized to supply an additional volume of refrigerant to the evaporator coil. The evaporator coil then would need to have a psychical internal area large enough to hold this increase in volume of refrigerant. We then must consider not just the BTUH rating of the condensing unit, but also the SEER rating of the equipment, in determining the proper size metering device and evaporator coil. At this point we must assume that the type of refrigerant being used is the same for each component as designed by the manufacturer. Normally the manufactures rate condensing units in BTUH or in laymen terms tonnage and in SEER or EER rating, but the Evaporator coils and metering devices are normally rated in tonnage only. This factor means that it would not be unusual to find a condensing units rated BTUH to be different from the rated BTUH of the metering device and evaporator to get the operating SEER of the system to match the manufactures SEER rating of the condensing unit. In addition, you can easily find examples of exceeding the manufactures SEER rating on a condensing unit, by modifying the type and size of the metering device and evaporator coil. Keep in mind the duct system design also plays an important part in determining the performance of the equipment used, but I have chosen to focus on the equipment only in this reply.
    I'm sure this cleared things right up for the HO
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  3. #16
    Join Date
    Jan 2006
    Posts
    21
    That is exactly why a customer needs to deal with a quality Licensed Mechanical Contracting company. The HVAC-R industry is extremely technical and complicated. Regardless of the amount of experience and training, no person is capable of knowing it all, as humans we just do not have the lifespan that would be needed. The general public for the most part has no idea of the amount of training and knowledge needed to be good at what we do. The customer, all customers need to hire an experienced professional that they trust, if you do not trust your contractor, hire one that you do and please take their advice. Being at the job site, seeing the job and accumulating all the data and being able to talk to the homeowner in detail about the job, means the contractor will know more about the job than anyone else and you should always trust what he tells you. The contractor’s job is to look out for his customer’s best interests and most do and if you choose to do so, you can always get a second on site opinion
    Ignorance is the lack of knowledge, Stupid is the lack of ability to gain knowledge.

  4. #17
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,923
    tulsatwisters; I am dyslexic and getting old, please punctuate. Thanks
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  5. #18
    Join Date
    Jun 2000
    Location
    WYO
    Posts
    2,019
    Paraghraphs would be nice as well.
    never say never

  6. #19
    Join Date
    Jan 2006
    Posts
    21
    Sorry RoBoTeq , I will try my best to do better.
    Ignorance is the lack of knowledge, Stupid is the lack of ability to gain knowledge.

  7. #20
    Join Date
    Jan 2006
    Posts
    25
    You can also try to make it short and to the point. I still don't understand what advantages or disadvantages, if any, for oversized coil. I've been reading that oversized coil can contribute to high humidity in the house, is it right?


    [Edited by lucky777 on 01-26-2006 at 11:01 PM]

  8. #21
    Join Date
    Jan 2006
    Posts
    21
    It is difficult to make an understandable point on a technically involved and complicated question.

    The general public without at least some basic knowledge of physics, psychometrics, electricity, electrical controls, etc., may have trouble understanding, what may by necessity, be an involved answer to what may seem to a layman a simple question.

    My point was that the coil might not be oversized, just because the BTUH rating or tonnage is different from the condensing units BTUH or tonnage rating. You have to take the SEER rating of the condensing unit into account.

    Even with my short (to me) four-line to the point answer, I have left out a lot of data that would need to be considered. It is not a simple question.
    Ignorance is the lack of knowledge, Stupid is the lack of ability to gain knowledge.

  9. #22
    Join Date
    Jan 2006
    Location
    McQueeney, Texas
    Posts
    3,725
    lucky777-
    Trane is dragging their feet in providing the new specs on the updated equipment so I haven't those answeres.
    I do show the rxco coils made for the 2 stage compressor systems. The ttr units are not 2 stage but that doesn't mean trane hasn't a match for it. I couldn't tell until I get the facts sheets and software.

  10. #23
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    15,847
    Originally posted by tulsatwisters
    Regardless of the amount of experience and training, no person is capable of knowing it all, as humans we just do not have the lifespan that would be needed.

    Some here are not going to like that statement.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law

    "Never let success go to your head, and never let failure go to your heart". - Unknown

  11. #24
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,923
    Originally posted by tulsatwisters
    It is difficult to make an understandable point on a technically involved and complicated question.

    The general public without at least some basic knowledge of physics, psychometrics, electricity, electrical controls, etc., may have trouble understanding, what may by necessity, be an involved answer to what may seem to a layman a simple question.

    My point was that the coil might not be oversized, just because the BTUH rating or tonnage is different from the condensing units BTUH or tonnage rating. You have to take the SEER rating of the condensing unit into account.

    Even with my short (to me) four-line to the point answer, I have left out a lot of data that would need to be considered. It is not a simple question.
    I think this states it very well (thanks twister )

    I keep hearing the term "oversized coil" when in fact, higher efficiency systems simply need "larger" coils to match the larger coil on the outside unit.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  12. #25
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,923
    Originally posted by mrbillpro
    Originally posted by tulsatwisters
    Regardless of the amount of experience and training, no person is capable of knowing it all, as humans we just do not have the lifespan that would be needed.

    Some here are not going to like that statement.
    Stirring crap? Maybe you would be more comfy in a toilet.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  13. #26
    Join Date
    Jul 2005
    Posts
    648
    An oversized evap w/txv will certainly run at a high superheat, providing alot less cooling for compressor. Resulting in eventual compressor/system component failure.

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