Page 2 of 4 FirstFirst 1234 LastLast
Results 14 to 26 of 49
  1. #14
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,439
    The concept of controlling humidity with only an a/c in the Mid-Atlantic states is a stretch. If you are a normal family with adequate fresh air infiltration or ventilation, over-cooling with not provide 50%RH during wet cool weather. There is not enough cooling load during wet cool weather with any of the sysems discussed to remove the 30-50 lbs./day of moisture needed to maintain 50%RH. Save some of that two-speed money for a whole house dehumdifier. These dehus have the ability to maintain <50%RH throughout the home without any a/c operation during wet, cool weather and fresh air, infiltration or ventilation. Many mfgrs. are offering this concept. A simple a/c will have less headaches long term than the more complex system. Sorry, I could not stay out of this discusion. But investigate the whole house dehumidifier concept used by many to deliver real humidity control for indoor air quality and comfort. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  2. #15
    Join Date
    Aug 2008
    Posts
    416

    Humidity Not the Issue (I think)

    Thanks for the reply and the whole humidity question is really a tangent to the original question of tweaking indoor coil for total/sensible performance.
    One poster (from Tx) asked about humdity in my area. I do not need nor plan on doing anything special with the xL16i/XV95 to control summer humidity. For what its worth my simple humidity meter (next to 1st floor return vent) reads 55% when current 3 ton AC running and jumps back to 60% when system off and I don't find this uncomfortable (thermostat set for 76*). I do agree that if RH was dropped, then setting therostat to 77* might also feel comfortable. So thought (based on Trane marketing) is that my two-stage xL16i will run longer at low speed and reduce humidity (maybe). If it doesn't I'm not sure it will be a problem.

    My major concern is that house measures 36200/31500 (Total/Sensible) thru NEW Manual J while original builders Manual J 15 years ago was 31538 (I believe Total). So I'm all confused if 3 ton Trane replacement will perform equiv. to existing 3 ton R-22 Comfortmaket and whether I should get twisted in a knot over newer Manual J number which indicates a need for 3.5 to 4.0 tons. Remember, I've been happy for 15 years.

    Biggest bugaboo is contractor tells me 3 ton xL16i with 4 ton coil (ARI# 1299074) will only give 34400/24200 (Total/Latent) which doesn't meet NEW Manual J but meets OLD calculation.

    Also, how would 55% RH in house affect the 34400/24200 number above?? Were they calculated at a certain RH??? If I accept the 55% I have now are the performance numbers better. If system runs and reduces RH will performance in BTUs of sytem go up as some have suggested??? I really don't understand the interactions..

    Most people just replace the existing unit with equivalent if there are happy with old performance (as was I). Unfortunately, I asked for and got a Manual J thats just twisted me up in knots and is causing me to lose sleep....I really am beginning to beleive that "ignorance is bliss"....Ah, the curse of being an engineer....

  3. #16
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,088
    Your current contractors calcs are wrong period.
    Your current 3 ton proves that. No ifs, ands, or buts about it.
    The 3 ton OD with a 4 ID will probably increase your humidity, because in first stage, it will have closer to an 80&#37; sensible capacity.

    The 3 ton indoor coil will give you better latent at lower temps.
    Then when its hotter out, with the indoor humidity low, you will get half of the latent capacity back as sensible.

    Ask your contractor to explain how your current 3 ton works, if you really need a 4 ton.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #17
    Join Date
    Aug 2008
    Posts
    416

    Explain with Real Numbers

    I' beginning to agree that NEW calcs are wrong. I used an on-line short form calc and the house blueprints and was almost able to duplicate original builders number for Total of 31538 (was off by 400). After house was built increased attic insulation from R-30 to R-38, so I tweaked calc and got:

    30,425 Total and 23,404 Sensible (all at 95*/75*) (a factor of 1.3 was used by calc). So I gather Latent is 30,425 - 23,404 = 7,021

    Now, I'm mostly worried for mid summer when I need xL16i running at capacity. So 3 ton xL16i with 4 ton coil at 2nd stage will give (from contractor):

    34,400 Total and 24,200 Sensible (does that give Latent = 10,200)

    So I meet those numbers and I don't have 1st stage numbers for this set up.
    Could you explain the humidity delta in terms of these numbers?? I am trying to grasp the concepts...

    If possible, walk me through what happens when unit starts in 1st stage at 80% and then since mid-summer, 2nd stage kicks in... I'm really curious about the Latent returned as Sensible. Are you saying that in above conditions I need only 7,021 per calc but unit is supplying 10,200 so that 1/2 of excess (0.5 * 3,179 = 1590) is returned boosting my Sensible to 24,200 + 1590 = 25,790 Sensible Available...

    I understand your concerns about Latent in 1st stage and Humidity removal, but there are competing concerns when running at 2nd stage and I am having trouble setting my mind at ease......

  5. #18
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,088
    You have the latent to sensible right.

    The unit will start in first stage every time. If it can't maintain temp, it will go to second stage. First stage will always have a higher SHR then second stage. The blower won't slow down enough to get a lower SHR. (16i)

    Since your meter is already showing that your current 3 ton, is not getting the humidity below 55&#37;, you need a coil with better latent capacity in first stage.

    You'll get enough sensible from it, on your hot days to handle the load.

    I don't have performance sheets for your unit, so I can't give detailed SHR performance

    But, the 3 ton coil in second stage exceeds your sensible requirements of your load calc you just did.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #19
    Join Date
    Aug 2008
    Posts
    416

    Going from 3 ton single-stage to xL16i and humidity

    Thanks for confirming my thoughts and I agree/understand what you are saying that 3 ton OD / 4 ton ID is not as ideal at 3/3 combo for humidity in stage 1. I don't have numbers and they must be at least one negative to upsizing coil.

    If I follow everything your're saying: Can we agree that moving from the old 3 ton single stage to the 3 ton xL16i with 4 ton coil will lower my humidity because its a 2-stage???

    If I follow the concepts. Currently, old unit comes on and pumps 26K (guess) Sensible and then shuts off when temp drops. Not so much humidity removed as evidenced by 60% RH on meter when unit shuts off.

    Now, with 2-stage xL16i, unit comes on with lower Sensible and lower blower and runs longer, hopefully removing more moisture before satisfying demand and/or kicking in 2nd stage. Now we don't have all the numbers, but is it somewhat safe to say the xL16i (whether 3 or 4 ton coil) will lower the humidity when compared to old 3 ton unit?????

  7. #20
    Join Date
    Feb 2007
    Location
    S.E. Missouri
    Posts
    258
    Please listen to the pros on here. I myself had a system where the contractor put a 4 ton coil on our properly sized 3 ton outdoor unit. Here in Swampeast Missouri, I can tell you that the indoor humidity was very hard to keep below 60&#37; without running the t-stat down.

    Now we have a new 2 stage system, outdoor unit is still a 3 ton nominal, but indoor coil is rated at 3 tons also. We now have between 40-45% humidity and keep the thermostat around 75-76 degrees.

    By the way, you can control the XL16i with the TCONT402 thermostat and a humidistat control. It's not integrated, but can easily be done. This will be able to control both first and second stage airflow.

  8. #21
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,088
    Quote Originally Posted by wraujr View Post

    If I follow everything your're saying: Can we agree that moving from the old 3 ton single stage to the 3 ton xL16i with 4 ton coil will lower my humidity because its a 2-stage??? No, it may not remove as much.



    Now, with 2-stage xL16i, unit comes on with lower Sensible and lower blower and runs longer, hopefully removing more moisture before satisfying demand and/or kicking in 2nd stage. Now we don't have all the numbers, but is it somewhat safe to say the xL16i (whether 3 or 4 ton coil) will lower the humidity when compared to old 3 ton unit?????
    No, thats saying both coils will remove the same amount of moisture per run time. And since one has a larger surface area then the other. It won't
    Its easier to get a couple hundred extra sensible BTUs from a smaller coil, then it is to get more latent out of an over sized coil.

    Its your money. You want higher humidity then you have, get the 4 ton coil.

    Keep in mind, that your current 3 ton, has a lower SHR then the 2 stage will have in first stage.

    I live in an area with a lot of low load days, the larger coils are not the way to go with 2 stage units. Very seldom do I use the larger coil, I'd rather lose ˝ a SEER, and keep the humidity down, then have someone tell me the humidity is high, so they have to set the stat lower to feel as comfortable.
    And aren't seeing much in the way of savings.

    EG: On a York 3 ton 2 stage, comparing a 4 ton coil to smallest coil rated for the 3 ton condenser, the SHR is lower by almost 5% in first stage. But holds the same SHR in second stage as the 4 ton coil.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #22
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,001
    Quote Originally Posted by Silver06 View Post
    I myself had a system where the contractor put a 4 1/2 ton coil on our properly sized 3 ton outdoor unit.
    Yep them "4.5" ton coils are not good to use with a 3 ton condenser, by the way what brand of coil was
    that 4.5 ton coil? I bet it was a Toshiba.
    __________________________________________________ _______________________
    “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

  10. #23
    Join Date
    Feb 2007
    Location
    S.E. Missouri
    Posts
    258
    Quote Originally Posted by Mr Bill View Post
    Yep them "4.5" ton coils are not good to use with a 3 ton condenser, by the way what brand of coil was
    that 4.5 ton coil? I bet it was a Toshiba.
    Mr. Bill, you got me

    Long day. Yes, they come in whole sizes. Was an ADP coil. They did not use the piston that came with the outdoor unit. No TEV

    Yeah, that was a metric coil. LOL

    Not joking about the 402 t-stat though.

  11. #24
    Join Date
    Jan 2007
    Location
    N.E. Ok.
    Posts
    1,370
    last 4.5 ton coil i saw was actually a 5 ton but with the install paperwork still inside.
    It was a rough guess but i figured it gained about 6000btu's when removed

  12. #25
    Join Date
    Dec 2002
    Location
    Houston,Tx.
    Posts
    16,001
    Quote Originally Posted by captube View Post
    last 4.5 ton coil i saw was actually a 5 ton but with the install paperwork still inside.
    It was a rough guess but i figured it gained about 6000btu's when removed

    That's Funny!!
    __________________________________________________ _______________________
    “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

  13. #26
    Join Date
    Aug 2008
    Posts
    416

    No Disagreement Here

    I am in no way disagreeing or not listening to the replys. I am consumer stuck in the middle with contractor saying one thing and your replys saying similar and different things. Remember contractors generally don't take advice from homewners. Second, I have no access to Trane data, so analyzing what happens in first stage with SHR is beyond my scope and I am left with maybes and possibly.... I also have no data on my 15 year old system to know its SHR and how it would compare. So I am stuck with either trusting the contractor I've used for 20 years or tell him to not install the system on Tuesday because of my "analysis" and internet advice. Don't get me wrong I truly respect and appreciate the advice being given. Just try to understand where I am positioned.

    At this point my only question, which will probably go unanswered as I have no numbers to analyze is "Will the xL16i with an AHRI matched 4 ton coil remove less humidity in the 1st stage than my old 3 ton single stage AC?" My contractor implies not while the experts say maybe (because we don't have data).

    As for your 4.5 ton coil with 3 ton condensor example, there appear to be no Trane matches in AHRI database so clearly yours was a bad design. That doesn't mean a 3OD/4ID combo is bad, just maybe not perfect.....

Page 2 of 4 FirstFirst 1234 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event