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  1. #1
    Join Date
    Jun 2001
    Posts
    22
    I just resently built and moved into a new house. I had a dual HVAC system installed (split upstairs and downstairs).

    The house is 3670sqft, and I have 2.5 and 3.5 ton AC units. The 3.5 is connected to the lower level system and the 2.5 is connected to the upper level system. Both furnace/HVAC units are in the basement.

    I know more then the average Joe, but a ton less the the less then average Joe HVAC guy. So I have some questions so I can sound knowledgable when I question this installation.

    The house is 2 stories, and has 2 "mid-level" dens off to the side of the main structure. Half way down to the basement you land in the lower den, and half way up to the second floor your land in the upper den. Both of these dens are on the upper level (smaller ton) HVAC System.

    All totaled up:
    Upstairs 2.5 ton unit has 2195sqft
    Downstairs 3.5 ton unit has 1475sqft

    Just going by SQFT and the fact that the upstairs is going to be harder to cool because the living space is in direct contact with the attic space above, also the air has to be pushed upstairs from the basement, loosing some of its cooling power on the way I would assum...should this not be reversed?

    Both furnace units are the same, the A-Coils are properly matched to the outside unit that is connected to them.

    Did they install the AC units backwards during the installation? Am I crazy?

    I have an outstanding "free call" for them to come and properly charge the units once the temp gets above 70 outside (so they can be charged correctly, they were installed in January). They are also going to balance all of the dampers (all of the output and input ducts have manual dampers). I just wanted to make sure that the smaller unit upstairs makes sense, or am totaly off base and it could possibly be correct.

    Let me know if you need more details...just trying to keep it simple if possible.

    [Edited by aejanis on 04-04-2005 at 01:41 PM]

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Sounds like the larger one ,needs to be "upstairs",based on sq. ft.,but windows and the direction they face also play a major factor in cooling size,how do they compare?Plus the attic has a lot to do with cooling load ,and a first floor could have none or very little.


    Lower den sounds like it would be on the 1st floor system,are you sure it's not?

    They could have easily switched the coils,certainly worth asking.

  3. #3
    Join Date
    Jun 2001
    Posts
    22
    House faces due East. House is pretty even with windows upstairs and down stairs. There is one window less downstairs...but a sliding glass door is in its place when compared to upstairs. Otherwise the window count the directions that they are facing is matched. There are no windows facing south anywhere on the house (by my request/design )

    Only other thing that could come into play is that there are 9ft ceilings downstairs vs 8 foot ceilings upstairs.


    The lower den is no doubt on the upper level HVAC system. They share duct returns and sends mains that break off to each room before the go into the walls (sends are in the ceiling on the lower den, and in the floor in the upper, returns are home run).

    [Edited by aejanis on 04-04-2005 at 02:36 PM]

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Any difference in wall construction/insulation,between 1st and 2nd floor??


    Your city and state??

  5. #5
    Join Date
    Jun 2001
    Posts
    22
    Oswego, IL (chicago area)

    No...all outside walls have the same insulation.

    Exterior insulation R-13,
    flat floors betwen lower ceiling and upper floor R-11 (noise control added at my request)

    R-38 combination batt and blown in the attic, attic space covers the entire second floor and upper den

    FWIW...here is a link to the floor layout. My house is a mirror image. I moved the lower level den window to the West facing wall. We don't have a 4 season room or any bay windows. We have the optional 5th bedroom upstairs. Also the SQFT advertised does not include the lower den because it is below grade, but we had it finished and would be counted in the heat/cooling.

    http://www.wisemanhughes.com/communi...fp_laurel.html

    [Edited by aejanis on 04-04-2005 at 02:48 PM]

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Unless I'm misssing something,I'd think the upstairs,due to the attic space above,would require the most cooling.

    The downstairs has the kitchen load and it's common to count 2 people per bedroom,and put those btus/people in the living area which is down stairs,but I'd think the attic would still make the 2nd the same or greater btus for cooling.

    I'd also think the first floor might need a larger furnace than the second,but I could easily be mistaken,as I'm in Florida.

    Wait for some other opinions,to be sure.

  7. #7
    Join Date
    Jun 2001
    Posts
    22
    FWIW...I really need to verify the furnace sizing...the downstairs one might be larger then the upstairs...I seem to recall the docs having to different model #'s, but I didn't look for BTU ratings on them....stay tuned for that.

  8. #8
    Join Date
    Apr 2004
    Posts
    7,680
    Hmm that slider and the appliances might be some of difference but with the dens connected to the upstaires unit you may be right. Why not contact the installing firm and see if it might have been a mistake.

  9. #9
    Join Date
    Jul 2004
    Posts
    322
    It's possible they just made a mistake, since the upstairs is smaller in nearly all houses. But I also know from experience that the actual duct layout is sometimes not what you assume.

  10. #10
    Join Date
    Jun 2001
    Posts
    22
    Originally posted by fat bob
    But I also know from experience that the actual duct layout is sometimes not what you assume.
    Very hard to make that mistake in this situation...

    The installer did a very good job of marking every single duct with the room that is it coming from and going to. During the pre-drywall I did a good job of annoying my wife by walking the entire duct work path to and from every room to verify that they were labeled correctly.

    Every duct coming and going is labeled and dampered with a manual damper. I was quite impressed with the work that was done. That is why I am posting here....I don't want to question their work because they did such a good job with the installation.

    [Edited by aejanis on 04-04-2005 at 06:37 PM]

  11. #11
    Join Date
    Jun 2001
    Posts
    22

    Corrections and additions..

    I have a 3.0 ton and a 2.5 ton, mistake was that I thought I had a 3.5 and a 2.5.

    Here is a breakdown:

    First Floor:
    Lennox AC Unit: 10ACC-036-230-02 (3.0 Ton 10 Seer)
    Lennox Furnace: G40UH-36B-090-09 (1/3 HP Blower)

    Second Floor:
    Lennox AC Unit: 10ACC-030-230-03 (2.5 Ton 10 Seer)
    Lennox Furnace: G40UH-48B-090-07 (1/2 HP Blower)

    So the furnace units seem to be correct for the job...the larger HP blower unit is working for the second floor. That makes sence because it needs to force the air up to the second floor from the basement.

    So the question that I am still looking for the opinions on..should the 3.0 Ton Unit be upstairs or downstairs based on:

    2.5 ton of AC cooling ~2195sqft of upstairs with attic above with "mid-level" dens (one with attic above and the second halfway underground).

    3.0 ton of AC cooling ~1475sqft of downstairs with a kitchen and 9ft ceilings throughout.

    All walls, windows and insulation being basically equal.

    I have a call into the builder to have them check out the way it should be. Since I was off by .5 tons the gap on the differance has closed some...so it might come down to sizing based on other things that are known to them and not to me.

    [Edited by aejanis on 04-04-2005 at 06:39 PM]

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