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  1. #1
    Join Date
    May 2005
    Location
    Haverhill, MA
    Posts
    14
    Hello folks, I am looking for any insight into the matching (or miss-matching) of the components in the system that was just installed into our house, which I am contracting. The installer was a sub of my plumber, and he seemed a very decent bloke, and a good mechanic.

    I did an analysis myself using HVAC-Calc before the install, just to confirm the figures. The results were Gain 37.2K and Loss 33.9K

    The split system components installed were…
    Furnace: Trane XL90 - TUX080R942W (LP Gas conversion)
    Indoor Boxed Coil: Trane - 2TXCB042AC3HCAA
    Outdoor Unit: Trane - 2TTB3036

    The system is controlled by a Honeywell VisionPro 8000 (TH8321U1006), which I purchased along with a remote outdoor sensor.

    From the figures I am able to find it would seem that the components are up to the job, am I right? The indoor coil is the biggest mystery to me, as I can find no specific info on it, does it seem like the right choice to you guys, what sort of realistic SEER rating will it produce paired with that outside unit? Any comments in general?

    Thanks
    James


  2. #2
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    That combo is an ARI listed match, 10 SEER

  3. #3
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,189
    Cut and pasted from ariprimenet.org:

    Today's Date 12/30/2005 01:29:04 PM
    Created Date: 09/29/2005

    Last Modified Date: 09/29/2005 at 02:01 PM
    Status: Active

    Obsolete: No
    Manufacturer: THE TRANE COMPANY

    ARI Reference Number: 585656
    ARI Program: AC
    ARI Type: RCU-A-C

    Trade/Brand Name: XB13
    NAECA Designation: Yes

    Outdoor Model Number: 2TTB3036A1

    Indoor Unit(s): 2TXCB042AC3
    Ventilation Rate:
    Product Performance Ratings
    ARI Rating
    Cooling Capacity (Btuh): 33800

    SEER Rating (Cooling): 13.00
    Realistic SEER? That depends on the installer and his craftsmanship. It also looks a bit short on capacity, but you should only notice on extreme days if the duct is designed and installed properly. The ARI capacity number is also lower than most actual design conditions.

    [Edited by jrbenny on 12-30-2005 at 01:15 PM]
    Perhaps you should have read the instructions before calling.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,151
    The furnace is grossly oversized! Output over twice the heat loss makes NO sense at all!

  5. #5
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,189
    Yikes. Just a tad bit too much furnace. Missed that one.
    Perhaps you should have read the instructions before calling.

  6. #6
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    Whoops, wonder what I looked up?

  7. #7
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    2TTB0036, I missed the 3

  8. #8
    Join Date
    May 2005
    Location
    Haverhill, MA
    Posts
    14
    Thanks very much for the replies guys…

    I can see the figure on the AC capacity, as you point out ‘jrbenny’, is a bit light given the heat gain figure; hopefully it can be lived with. If not is there another inside coil that I could ask them to install in the future that would be a better match?

    Is the furnace really that oversized, given that I added no percentage of a buffer to the heat loss figure I posted here, and also hopefully there won’t be a lot of need for the second stage to kick on?

  9. #9
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    This is just a guess, so take it for what it's worth.

    I've heard a lot of contractors that tend to oversize (not by just a little bit either) when they use 2 stage equipment. Not a good idea of course... size the equipment properly and let it do it's job like it's supposed to. Once you start 2nd guessing the load calc's, equipment spec's and that kind of stuff there's a huge oppertunity for problems to occur.

  10. #10
    Join Date
    Jan 2002
    Location
    Ft.Worth,Tx
    Posts
    4,584
    That is a (2) stage 90% furnace
    Tux080R942-airflow (3)ton (2)stage=73,300 (1)stage 48,600
    A.F.U.E. 93.0 %
    2TXCOB042AC3 33,400 BTU RATED
    2TTB3036A1000-13.0 S.E.E.R.
    You might want to go with-2TXCO54S3HPC Better rated coil with TXV
    "Everyday above ground, is a good day".
    "But everyday that you have made a difference in someones life, may insure you stay above ground a little longer".<aircooled>

  11. #11
    Join Date
    May 2005
    Location
    Haverhill, MA
    Posts
    14
    Well setting the furnace size aside and looking at the AC capacity, I read through 300 and some odd condenser/coil combinations (thanks for pointing me toward ARI dir) and it appears that none would increase capacity by more the a few 100 BTUh. The coil they installed paired with a move up to a 2TTB3042A1 would be ARI rated at 40K, which is practically the same amount over capacity as the current combo is under. So I wonder if I am just splitting hairs, and that if “jrbenny” is correct about the ARI figures being conservative then I will be alright?

    This is all naval gazing really, the equipment is in, and I will have to spend a year with it to see how it shapes up, but it surely helps to gain this knowledge if however a bit belated, and I thank you guys for sharing your insight.

  12. #12
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,151
    The heat loss calcs include some fudge so you should have to add any to be safe. So, yes, you are that oversized sorry to say.

  13. #13
    Join Date
    May 2005
    Location
    Haverhill, MA
    Posts
    14
    Originally posted by BaldLoonie
    The heat loss calcs include some fudge so you should have to add any to be safe. So, yes, you are that oversized sorry to say.
    Ok, the only reason I bring this up is because the publisher of HVAC-Calc 4.0 makes particular note of the fact that there is no margin built in, and he personally recommends a factor of 20-25% addtional. At 25% that would bring the design to 43,375-BTUh loss, still leaving me oversized nontheless, but perhaps not as bad I guess?

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