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  1. #1
    Join Date
    Jun 2008
    Posts
    58

    New Construction AC selection ?

    I live in Lower IL and we get the gambit of weather here. 90 + degree summer days, Humid, and Cold winters. I am in the process of buying a new house. It is going to be 2 story 2500 square feet. The contractor uses Lennox brand AC equipment. The norm for this house plan is


    Upstairs- Lennox ACD13 2.5 Ton with a G43 70k, 90% furnace

    Downstiars ACD13 2 ton with G43 45k , 90% furnace.

    I am looking to upgrade possible to the XC15,16 or 21 allong with an equivalent vari-speed Furnace.

    What do you think about putting the larger furnace on the first floor instead of the second?

    Do you have any reccomendations about a set up what type of info do I need to get a better understanding if these are addiquite units.

    Is there a way I can compare the ammount of savings I possible could get comparing the units.

    Thank you for any advice you can share.
    Last edited by acnoob1; 06-10-2008 at 08:28 AM.

  2. #2
    Join Date
    Dec 2007
    Location
    Cedar Grove, Wi-Sheboygan
    Posts
    1,582

  3. #3
    Join Date
    Dec 2006
    Location
    Dallas
    Posts
    189
    Here's a thread from few days ago in response to High SEER payback.

    http://www.hvac-talk.com/vbb/showthr...55#post1883255

    You are at 1400 hours or less of cooling per year, two 21 SEER systems would take a decade or two to offer any savings over 14 SEER after the initial investment.

    Same type of math applies to going above 90% furnace, but the payoff is probably faster.

    As far as larger furnace location - ask the contractor for Manual J load calculations. They should be able to tell you the heat loss for each floor and room.

    I would also explore a window upgrade. It saves you money during the winter and summer.

    4.5 tons cooling for 2400 sq ft = 533 sq ft / ton. This sounds like it could be approaching oversizing for quality construction in Illinois.

    I'm 1995 construction in Dallas, R8 ducts with near zero leakage at 710 sq ft / ton and I haven't hit stage two cooling on my single 5 ton unit yet this summer (99F High). A year ago I spent my extra $$$ on installation, ducting and zoning.

  4. #4
    Join Date
    Jun 2008
    Posts
    58
    Thank you for your replies, keep them coming.

    I will get with the contractor and get the heat loss calculations. Is there a cooling calculation as well?

    I deffinitely do not wan't an oversized unit. That happened to me when stationed in Alabama, wow was that a CF to get straightened out.
    Last edited by acnoob1; 06-10-2008 at 12:04 PM.

  5. #5
    Join Date
    Mar 2008
    Location
    Grundy Co. IL
    Posts
    773
    Ask for a price on the G-71 series furnaces, very nice.IMO

  6. #6
    Join Date
    Jun 2008
    Posts
    58
    I have been surfing all over the web to find out what sort of gains you get by upgrading I even contacted Lennox with no help there. Am I to assume that a carrier seer 16 or trane 16 should be relatively the same. When it comes to efficiency numbers?

  7. #7
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Quote Originally Posted by acnoob1 View Post
    I have been surfing all over the web to find out what sort of gains you get by upgrading I even contacted Lennox with no help there.
    Better comfort with energy savings (from higher SEER equipment). Heat rises, so I'm surprised to see the larger furnace (especially one that has 35k more capacity) on the second story. The Lennox Signature Series system is very nice (which would be the XC15/XC21 with G71P, or you could go with a heat pump and a 80% AFUE furnace, the G60V, as backup).

  8. #8
    Join Date
    Jun 2008
    Posts
    58
    That was my concern as well. With Heat rising and all. I am going to meet with the guy here in the next day or so. I am going to get load calcs ect, Prices on the upgraded units. Then I probably will have 20 more ?'s

  9. #9
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    Ask away. And by the way, should that be 13ACD or AC13? My guess is that they are 13ACD's with just a transcription error. Two different products as far as quality and features go. This is your house--I think you might benefit from going to at least an Elite series outdoor unit with a variable-speed indoor unit.

  10. #10
    Join Date
    Jun 2008
    Posts
    58
    Yes you are correct it is the 13ACD. I am thinking that the most economical choice is going to go with the xc16 and a g61 or g71 furnace. I don't think I am missing anything else, am I?

  11. #11
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    You're on the right track toward a good system. The XC16 or XC21 (or heat pump equivalent for a dual fuel setup) along with a variable-speed furnace (G61V or G71MP) should be a great setup. That would provide you with a great system (that provides great comfort and energy savings at the same time) to enjoy in your new home. Don't forget a good thermostat, such as the Lennox Comfort Sense (L7742U) or VisionPRO IAQ, to control the system, as well as a good ductwork system (I prefer insulated metal trunklines with flex duct connectors).

  12. #12
    Join Date
    Jun 2008
    Posts
    58
    Ryan, Thank you for the info, I will be looking into the iaq thermastat as well. I just need to come up with some prices then I can make my cost analysis. It is like pulling teeth to get somebody to give me a price on equipment. Even after explaining my situation.

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