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  1. #1
    Join Date
    Sep 2006


    Hi all, I've been lurking for awhile trying to gain as much knowledge (at least the ability to ask the right questions) as possible before purchasing a system. And I must say, I'm glad I found this forum, it contains a wealth of knowledge. Ok so here goes the details and my few questions...

    Home is a 1783 SQFT Tri-level (crawl space) in the Seattle area built in 1981.
    13 output Registers
    1 Return on 1st floor.
    23 Windows (old aluminum double paned)
    Front of house faces West.

    Currently have central heating using the original electric furnace. The Utility company in the area is offering a very low % conservation loan program to assist homeowners changing over to more cost effective form of heating. The utility company did a heat loss anaylsis for me and then gave me a number of "approved" contractors to give me bids based on the Utility companies calculations, the systems must meet certain requirements, etc..

    Heat Loss = 41419 BTU's/hr at design temperature of 20 degrees.

    Based on this number can anyone give recommendations on proper sizing? I am concerned with oversizing.

    Having difficulty deciding between two contractors (one installs Trane and other installs Carrier). Both Contractors have good reputations in the area although the Trane guy seems more knowledgable (or at least more sure of himself). Here is what they recommend...

    Carrier Infinity 16 Series
    Outdoor model #25HNA648A003 (4 ton)
    Indoor model #FE4ANB00600 (4 ton)
    Infinity t-stat
    set of Carrier Intelligent heat strips (5,15 KW) model #KFCEH3101C15

    Trane XL16i heat pump
    Outdoor model #4TWX6036B1 (3 ton)
    Indoor model #4TEE3F40A1 (3 ton)
    10 kw heat strip
    Honewell pro8000 t-stat

    I am concerned that the 4 ton is oversized (although the Carrier guy insists that this is the correct size, he states that I spec out for 3.5 tons so because no half tons for the system he rounds up). Also claims since the Infintiy is a "Communicating" variable speed system that the system will automatically adjust down to what is needed while running and therefore will be just as efficient as the smaller 3 ton, but with the capability of 4 ton if needed on those extra cold days.

    Trane guy insists that 3 ton is appropriate and 4 ton is too large, claims that that would be a lot of air whipping around for 13 registers and feels duct work might need to be increased in size (affecting overall cost obvisouly).

    Utility company tells me that either system falls within their requirements (because they are both 2 stage variable speed systems), but his personal opinion is that the 3 ton would probably operate more efficiently.

    Any comments or opinions are much appreciated.

    I like both systems. Heating efficiently (lowering my portion of the heating bill) and being comfortable in the winter are my main goals. The A/C is just an added bonus for me as there is only a month maybe two a year which I wish I had A/C.

    Any Opinions on Trane Vs. Carrier (for mentioned models)?
    Trane has the scroll compressor, Carrier does not. Carrier is a time/temperature defrost cycle, Trans is the other.
    Do these 2 facts really make that much of a difference and therefore Trane is the better system?

    Is 4 ton oversized?
    Is the "intelligent" heat strip (5,15) worth the extra money?

    I'm considering adding the electronic filter instead of 4" media filter. Is the cost worth it?
    Carrier = carrier electronic air filter
    Trane = Honeywell F-300 electronic filter (recommended because Trane guy says it is quiter than Tranes electronic filter).

    Thanks in advance,

  2. #2
    Join Date
    May 2000
    Indianapolis, IN, USA
    4 ton for 1800 sq ft in Seattle sounds grossly oversized to me. We run hot & humid all summer and that size house runs 2 to 2.5 tons depending upon insulation & direction of windows. Demand to see their heat GAIN calculation. Oversized, even with 2 stage equipment, isn't wise. You'll run on low only and defeat the purpose of spending a fortune on 2 stage equipment.

    How often do you hit 20°? If annually, then the Trane dealer ought to be putting in 15kw. The backup should be sized to the heat loss.

    Personally I would go with the media filter.

    As for which system, the Carrier Infinity will do much more than the Trane with the Vision Pro. I like the 50/100% staging vs the Trane. While demand defrost is nice, in your climate you won't be needing many defrosts so I wouldn't worry about that. Just worry about the sizing of the heat pump.

  3. #3
    Join Date
    Sep 2006
    Thanks Baldloonie,

    You asked a rhetorical question that I'm going to answer because it reminded me of another question about balance point "how often does it reach 20 degrees?"

    I don't think it ever does and according to the average min temperature in January (coldest month) is 36.4 and the number of days annually it is below freezing is only 19 days.

    So if I calculated the balance points correctly for each system, the 3 ton Trane should be roughly 34 degrees and the 4 ton carrier should be about 28 degrees. I also calculated the 3 ton Carrier balance point which is about 35 degrees.

    Do I make any sense or is this all jibberish I just posted (if so sorry )?

    Anyway, if not jibberish, than am I correct to believe that the 3 ton Trane should heat my home down to about 34 degrees F before auxillery heat kicks on?

  4. #4
    Join Date
    Nov 2004
    Originally posted by BaldLoonie
    4 ton for 1800 sq ft in Seattle sounds grossly oversized to me. Demand to see their heat GAIN calculation.
    I think he was saying it sounds oversized for cooling.
    (heatpumps are usually sized based on heat gain calc.,or cooling need.)

    Anyway, if not jibberish, than am I correct to believe that the 3 ton Trane should heat my home down to about 34 degrees F before auxillery heat kicks on?

    yes ,sounds close .If you are patient and allow the system to run long enough. But, if you get chilled,you can knock it up a notch and bring the auxillary...

  5. #5
    Join Date
    May 2000
    Indianapolis, IN, USA
    The average home around here we put a 3 ton unit in has a heat loss of 65,000 BTU and we put a 20kw kit in to back it up. Most can get into the upper 20s before they need backup assuming 68-70° indoor temp and no setback. But the average home around here with a 3 ton is 2500 sq ft and we size to 95 out and humid!

  6. #6

    Did you get the Trane XL16i or Carrrier?

    I know this is a long shot since this thread is ancient, but I'm also in Seattle and just purchased a Trane XL16i 3 ton unit.

    If you did end up buying the Trane XL16i 3 ton instead of the Carrier 4 ton, did you like it? How is it in cold weather? I've heard they are lack luster, but couldn't we worse than my ancient system.


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