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  1. #1
    Join Date
    Feb 2008
    Location
    Colorado
    Posts
    38

    Cool Please help me decide which Modulating furnace to get

    I am thinking of upgrading my oversized 90,000 btu 5 ton Goodman 96% with the ECM motor furnace, to a smaller modulating one. I currently have the 5 ton choked down to the lowest first stage W1 with -10% on.

    Being a Contractor I can get a good price on Amana, Rheem, and Trane. I understand the Rheem has 13 speeds, the Trane 3 speeds, and not to sure about Amana. I will be doing a manual j now that I have new windows and R50 in the attic.

    My 2,600 sq foot house in Colorado, will need about 75,000 Btus input, with a 4 ton blower for the 3 ton AC. I am leaning twords the Rheem or Trane, since noise level is a big concern.

    Please help me decide!!!! What are the pros and cons of modulating furnaces?

    Thanks,

    Bob

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,165
    We've sold dozens of Rheem mods, I love them. Easy to work on, they stage up & down with the matching thermostat. We just did a RGFG with the high def communicating control, slick setup. Trane's mod is true modulating too. The 3 stage is gone. Seems a lot more complicated. I've been through the training but here anyway, lots pricier so we've never sold one. I sold a lot of 2 stage furnace back in the day but didn't hear customers rave about comfort til the Rheem came out.

  3. #3
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,275
    If your exisiting 90k furnace runs you out of there I'd question the 75k load calculation also, 15k shouldn't make that much difference. The Rheem 60k mod may be plently, especially since you have tightened up your house. Be sure to give credit for all your house tightening when doing your manual J, and don't fudge input numbers. You may be surprised how low the calculation comes in, it may be 1/2 or less than what you are used to installing. Why do you want a 4ton blower for a 3ton AC?

    Rheem modulates with the matching thermostat (ideal), but will work as a 3 stage if used with a standard 2 stage thermostat. 1st stage is lowest BTU, 2nd is middle then times to high after 10 minutes.

  4. #4
    Join Date
    Feb 2008
    Location
    Colorado
    Posts
    38
    I just got back from the Tyler Texas Trane tour, and am really impressed with the XL950 comfortlink thermostat (gota love a 7in HD color screen), and the Nexia software! I am new to trane and will have to check into their Modulating furnace a little more.

    54regcab, I think you will be right about the 60,000btu being enough for my house. I have my ECM motor currently set for 1375cfm
    for my 3 ton AC, and that seems to be right for my air flow needs, that is why I am interested in the 4 ton blower. I notice the Trane
    only has a 3 ton blower.

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,275
    IMHO Rheem is one of the only manufacturers that "gets it" when it comes to providing higher power blowers with lower BTU furnaces. Other brands insist you buy oversized furnaces to get the blower capacity you need. Rheem is the only manufacturer to offer a 50k furance with 4 ton blower. Don't recall what the blower rating is for the Rheem 60k mod.

  6. #6
    Join Date
    Feb 2008
    Location
    Colorado
    Posts
    38
    I am leaning twords the Rheem unit. It looks like the 60,000btu modulating only comes in the 3 ton blower for Rheem, Trane, and
    Amana. You would think they would offer it in both 3 and 4 ton.

  7. #7
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,165
    You can tweak it up 10% over 1200 CFM if you want.

  8. #8
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,275
    1320 CFM will get you real close to the 1375 you have now. Is it worth oversizing the furnace to get an extra 55CFM in cooling mode?

  9. #9
    Join Date
    Feb 2008
    Location
    Colorado
    Posts
    38
    It sounds like the 3 ton +10% will work! I do have 17, 5" supply runs in the house so that is close.

    Thanks for all the help!

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