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  1. #27
    Join Date
    Jan 2006
    Posts
    21
    Originally posted by matt8085
    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.
    The above quoted reply is a great example of the type of question or in this case statement that could take pages upon pages to respond to.
    I am not necessarily indicating the statement is inaccurate, but it does encompass several different laws of physics that to discuss each in detail would take an enormous amount of time.

    Just a few short examples:
    1. Proper sizing of equipment
    2. Type and size of the TXV
    3. Latent & Sensible Heat
    4. Refrigerant saturation point and change of state
    5. The amount of heat loss/gain required in the Change of State
    6. The amount of heat required to change the sensible heat of a Superheated vapor
    7. The amount of CFM across the evaporator (As to how it effects the Sensible and Latent heat absorption of the refrigerant
    8. General maintenance habits of consumers (here are just two of the items that would relate here as examples: 1. Air Filter type and replacement
    2. Condenser coil maintenance
    9. Compressor design and construction
    10. Minimum and maximum operating conditions of a particular design of compressor

    I am going to stop at ten; to the relief of anyone reading this I am sure.

    A couple of other discussions could be had:
    1. On what is meant by “oversized” and the amount of over sizing?
    2. What is exactly meant by “a lot of Superheat”?

    Again I am not taking issue with the statement, just saying it is a very good example of how what could seem to be a simple question or statement, could in fact be very complex and take time to properly discuss.
    What I really like about the question is how well it points out the need for highly trained and experienced professionals.
    I have always felt that the vast amount of knowledge, training and experience we must acquire to be skilled at our profession is lost on the general public.

    Who would ever think it would be good ideas for NASA go down to the local fast food restaurant to hire mechanical or electrical engineers? How about a neighbor, friend, relative?

    Answer: No reasonable thinking person that I know of

    Who would ever think it would be a good idea for the homeowner to go down to the local fast food restaurant to hire HVAC-R engineers? How about a neighbor, friend, relative?

    Answer: A large percentage of the general public
    Ignorance is the lack of knowledge, Stupid is the lack of ability to gain knowledge.

  2. #28
    Join Date
    Jan 2006
    Posts
    25
    I already stated that I got 5 ton RXC061S3HPC0 coil and 3 ton 2TTR3036A condenser. RXC061S3HPC0 has High Efficiency Bleed TXV, coil specs are here http://www.aireng.com/clientuploads/Coils_etc/rxc.pdf

    I have electronic air filter. Assume that equiment will be well maintained and cleaned. All I need to know if with this type installation will perform well and last.

  3. #29
    Join Date
    Jan 2006
    Posts
    21
    Originally posted by lucky777
    I already stated that I got 5 ton RXC061S3HPC0 coil and 3 ton 2TTR3036A condenser. RXC061S3HPC0 has High Efficiency Bleed TXV, coil specs are here http://www.aireng.com/clientuploads/Coils_etc/rxc.pdf

    I have electronic air filter. Assume that equiment will be well maintained and cleaned. All I need to know if with this type installation will perform well and last.
    I do not know how many ways there are to say…….. Not enough information to give an accurate opinion.
    In reading it the above, it may seem somewhat rude, but that by no means is my intention.

    Providing the information below would be a start in analyzing the situation and determining if any corrective action is needed, but only a start.

    Model number of the air handling equipment
    Indoor and out door wet and dry bulb temperatures
    High and low side pressures
    Amount of Superheat
    Amount of Subcooling
    Total CFM from all supply registers
    Supply Air temperature
    Delta T across condenser
    Delta T across evaporator

    It is a cat chasing it’s own tail situation:

    If you could provide the above information ….. That would make you to at least some degree, an experienced technician.

    However,

    If you were an experienced technician you would not need any assistance

    The only way to resolve the matter, would be to contact a quality with references, licensed mechanical contractor for an on site evaluation.
    Ignorance is the lack of knowledge, Stupid is the lack of ability to gain knowledge.

  4. #30
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,962
    Originally posted by lucky777
    I already stated that I got 5 ton RXC061S3HPC0 coil and 3 ton 2TTR3036A condenser. RXC061S3HPC0 has High Efficiency Bleed TXV, coil specs are here http://www.aireng.com/clientuploads/Coils_etc/rxc.pdf

    I have electronic air filter. Assume that equiment will be well maintained and cleaned. All I need to know if with this type installation will perform well and last.
    PLEASE!!!!!! STOP stating that a coil has a capacity that is greater then what the outdoor unit capacity is. This cannot happen. What you have is a 3 ton system using a coil that is capable of handling 5 ton of nominal cooling when used with a less efficient system. IT IS NOT A 5 TON COIL!

    Now that twister is posting on this subject I too feel compelled to put this issue to bed. Twister is much better at organizing the specific details of the physical data then I am so my posting here is hopefully to aide what twister is stating.

    Twister; slap me fast if I misconstrue what you are stating because I like the way you put things.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  5. #31
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,962
    Originally posted by matt8085
    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.
    Why would the proper TXV not control the intended superheat as a TXV is intended to do? Under what conditions would the TXV not allow more refrigerant to pass into the coil causing the superheat to increase? If the TXV sensing bulb is maintaining a specific superheat based on the temperature of the suction line out of the coil, why would superheat increase?
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  6. #32
    Join Date
    Jan 2006
    Posts
    25
    Originally posted by RoBoTeq
    Originally posted by lucky777
    I already stated that I got 5 ton RXC061S3HPC0 coil and 3 ton 2TTR3036A condenser. RXC061S3HPC0 has High Efficiency Bleed TXV, coil specs are here http://www.aireng.com/clientuploads/Coils_etc/rxc.pdf

    I have electronic air filter. Assume that equiment will be well maintained and cleaned. All I need to know if with this type installation will perform well and last.
    PLEASE!!!!!! STOP stating that a coil has a capacity that is greater then what the outdoor unit capacity is. This cannot happen. What you have is a 3 ton system using a coil that is capable of handling 5 ton of nominal cooling when used with a less efficient system. IT IS NOT A 5 TON COIL!

    Now that twister is posting on this subject I too feel compelled to put this issue to bed. Twister is much better at organizing the specific details of the physical data then I am so my posting here is hopefully to aide what twister is stating.

    Twister; slap me fast if I misconstrue what you are stating because I like the way you put things.
    Thanks RoBoTeq! This was kind of an answer I was looking for! We can put this issue to rest now.

  7. #33
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,962
    This whole issue really is created by the way manufacturers designate their coils with capacity numbers. I have been fighting this for decades, to no avail. Maybe someday we will have only letter designated indoor coils. Then I can work harder on getting thermostat manufacturers to stop putting numbers on t-stats and only refer to the temperature as "Cool" (less then 65º), "Comfy" (66º-72º) and "A bit warmish" (over 72º)

    [Edited by RoBoTeq on 01-28-2006 at 10:18 AM]
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  8. #34
    Join Date
    Jan 2006
    Posts
    21
    Yes RoBoTeq one of my points was related to the TXV as to it would relate to superheat, another was evaporator pressure, as it would relate to humidity or latent heat removal within the structure.

    You are a lot better at quickly getting to the point than I am…. I am just too darn long winded and can’t seem to help it. Too old and set in my ways I guess LOL.
    Ignorance is the lack of knowledge, Stupid is the lack of ability to gain knowledge.

  9. #35
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,302
    Originally posted by lucky777
    I already stated that I got 5 ton RXC061S3HPC0 coil and 3 ton 2TTR3036A condenser. RXC061S3HPC0 has High Efficiency Bleed TXV, coil specs are here http://www.aireng.com/clientuploads/Coils_etc/rxc.pdf
    The RXC line was designed for R410a outdoor units. Why is it being used on a R22 unit? Is the TXV being changed?

    Looking at the spec sheet for the 3036 outdoor unit, NO R410a coil is matched nor is any "5 ton" or 060+ coil matched. We can argue all day long about using oversized coils but if Trane doesn't approve it, who knows what performance you'll get and with the improper TXV especially.

    There's just so much cooling out of a 3 ton system. If someone decides to put it on a much larger coil, that coil will run warm, TXV or not. Fine in the desert but not in a humid climate.

  10. #36
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,302
    [QUOTE]Originally posted by RoBoTeq
    Why would the proper TXV not control the intended superheat as a TXV is intended to do? Under what conditions would the TXV not allow more refrigerant to pass into the coil causing the superheat to increase? If the TXV sensing bulb is maintaining a specific superheat based on the temperature of the suction line out of the coil, why would superheat increase?
    TXV will help when using a big coil but at some point, the surface area and load of the large coil be so great that the TXV will be wide open and still not provide a cold coil. Cool out, warm in on a big piston coil will provide outrageously high superheat. But if you have a huge coil on a TXV, that can be avoided to a point. But with the large surface area, I still can see times when there could be a superheat above what the TXV can control.

  11. #37
    Join Date
    Jan 2006
    Posts
    25
    Originally posted by BaldLoonie
    Originally posted by lucky777
    I already stated that I got 5 ton RXC061S3HPC0 coil and 3 ton 2TTR3036A condenser. RXC061S3HPC0 has High Efficiency Bleed TXV, coil specs are here http://www.aireng.com/clientuploads/Coils_etc/rxc.pdf
    The RXC line was designed for R410a outdoor units. Why is it being used on a R22 unit? Is the TXV being changed?

    Looking at the spec sheet for the 3036 outdoor unit, NO R410a coil is matched nor is any "5 ton" or 060+ coil matched. We can argue all day long about using oversized coils but if Trane doesn't approve it, who knows what performance you'll get and with the improper TXV especially.

    There's just so much cooling out of a 3 ton system. If someone decides to put it on a much larger coil, that coil will run warm, TXV or not. Fine in the desert but not in a humid climate.
    I was told that 3036 is R410a. Isn't it?

  12. #38
    Join Date
    Jan 2006
    Posts
    25
    This doesn't look good. According to Trane 2TTR stands for R22 and 4TTR stands for R410A. RX in coil name means that it is R410A. So much about "Always trust your contractor". At estimate time I specifically asked about R410a system and was quoted one.

  13. #39
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,962
    Whoopsie...

    Not being familiar with Trane nomenclature I did not even think about the metering on the coil not being compatible with the outdoor unit.

    Baldy; thanks for the TXV/large coil clarification. I did put that out there as a rhetorical question. Like you stated; large coils with light capacity, high efficiency systems are fine in arid conditions but not if you need humidity control
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


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