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  1. #1

    17" Furnace with 21" A/C Coil?

    Hello,

    I have had multiple contractor estimates and multiple opinions on what I need and what will work correctly in my home. I am now confused.

    Question 1:
    I am thinking of going with a new Rheem 80% 2 stage Variable speed furnace 3 or 4 ton 75000 BTU but I have a 2 Ton A/C condenser with a 2 1/2 ton. The Rheen furnace is apparently 17" wide and the A/C coil is 21". One contractor said they would have to replace the A/C coil with a 17" coil - another contractors said they would be able to make the 21" coil work and there would be no air flow loss or problems.

    Which is correct and what ton size do I really need for my A/C to work without restriction?

    Question 2:
    I live in the Denver area so do I need to be sure the contractor uses a High Altitude conversion kit and adjust or replace the burner orifices?

    Thank you for any help you can provide!

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,907
    Your existing coil is 21" wide and a dealer wants to sell you a new one because his furnace is narrower? COMMISSION, not common sense. Odds are your new 34" furnace will be shorter than the old one and a good tin man would have no problem transitioning to it.

    Looks like from the install instructions orifice size change is needed. Your dealer should know this.

  3. #3
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,157
    I'd question the need for the 75,000 BTU furnace unless a load calculation was done.

  4. #4
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,529
    Are you only replacing the furnace ? If so why not get a 21 wide Rheem furnace to match up with existing coil? I just don't no if they make a 21 wide in 75,000 btu.

    While I don't understand why he would need to change the coil out with the 17 wide furnace, he could make a transtion to make it work properly.

    Where is the equipment located Closet, Mech. Room or Attic? Also why are thinking of changing the furnace?
    Last edited by duckman06; 10-07-2012 at 11:56 AM.

  5. #5
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,907
    The 21" wide Rheem has a bigger blower, lower temp rise. It won't go down to 800 CFM for his 2 ton air.

  6. #6
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,529
    Sorry I looked right past the part of the (2) ton being the size of his outdoor condenser.

  7. #7
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,603
    Quote Originally Posted by BaldLoonie View Post
    Your existing coil is 21" wide and a dealer wants to sell you a new one because his furnace is narrower? COMMISSION, not common sense. Odds are your new 34" furnace will be shorter than the old one and a good tin man would have no problem transitioning to it.

    Looks like from the install instructions orifice size change is needed. Your dealer should know this.
    B.L. is right (again). There will be no problem. Go with the 3 ton blower if they don't make a 2 ton blower. A X13 motor would be nice.

  8. #8
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,603
    P.S. The plenun (sheetmetal) is 21" wide, not the coil inside.

  9. #9
    Join Date
    Feb 2010
    Location
    Calgary, Alberta
    Posts
    1,091
    The answer to question 2 is yes.
    Most furnaces are rated 0-3500 or 4000ft
    If Denver is really a mile high then you'll have to derate

  10. #10

    High Altitude?

    I want to Thank you ALL for your information

    I am going with the 75000 3 ton 17" X 34" Rheem. I have asked about the High Altitude and the Contractor I was thinking about going with said they purchase the units already setup for this.... Is that true? I see Rheem has a separate High Altitude kit listed for each of the models - I don't see where they come already set?

    I guess you can't really suggest a Contractor in the Denver area? I have talked with at least 7 and seem to not be able to find that one who is giving me the right information and taking care of my concerns. I always checked the BBB, Yelp and googled each contractor before I called them. I'm still not feeling very comfortable.

  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,907

  12. #12
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,058
    Quote Originally Posted by sagcf View Post
    I want to Thank you ALL for your information

    I am going with the 75000 3 ton 17" X 34" Rheem. I have asked about the High Altitude and the Contractor I was thinking about going with said they purchase the units already setup for this.... Is that true? I see Rheem has a separate High Altitude kit listed for each of the models - I don't see where they come already set?

    I guess you can't really suggest a Contractor in the Denver area? I have talked with at least 7 and seem to not be able to find that one who is giving me the right information and taking care of my concerns. I always checked the BBB, Yelp and googled each contractor before I called them. I'm still not feeling very comfortable.
    Type in darctangant in the directory on this site. He is in Denver/Boulder. Quite knowledgeable

  13. #13
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    The supply houses in that area most likely do get the equipment from the manufacturers already set up for the altitude. Same price just have to order it that way.

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