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  1. #1
    Join Date
    Dec 2012
    Location
    Sagamore Hills, OH 44067
    Posts
    8

    Gas furnace size recommendation- Model J attached.

    Hello again,

    Spent some time with HVAC-Calc, a tape measure and the house to do a Model J. Took some time, but not all that difficult. It's an educational experience for sure.

    Attached is the report which is pretty accurate...I hope. We plan on replacing windows within the next year, but didn't include them. They can only make the house 'tighter', I suppose. If anyone would care to help us out and give a size recommendation, we'd sure appreciate it. If there's anything that looks out of line, please let me know.

    Thank you in advance,
    Steve

    House Manual J Detail_12-20 Final.pdf

  2. #2
    Join Date
    Dec 2012
    Location
    Sagamore Hills, OH 44067
    Posts
    8
    Just an added note, we're going with a Rheem RGRM (90+%) furnace and one of their AC units.

  3. #3
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,772
    I cannot open your link for the pdf file.

    Re. the windows, I suggest you make a copy of the job and change the windows on the copy to see what effect they have on the load.

    You may want to add your location to the post or put it in your profile. That will have an impact on the sizing.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,079
    My vote is RGRM-06 with 2.5 ton A/C. Prefer the good ones to the value cubes if budget permits.

  5. #5
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,215
    My house is the same size and can keep 75f inside with it 100 outside on a 2 ton AC. Manual J calls for 2 ton, don't oversize for the 3 days per year that it's over 88F.. Put some shades on the windows and drop another 1/2 ton in cooling load. Close shades on days when it's near design temps outside.

    I'd think strongly about some type of zoning/manual dampers that you can adjust seasonally. Otherwise the top floor will always be hot and the bottom floor cold. With 3 floors correct ductwork is CRITICAL to having even comfort through the home. Much more so than getting high end equipment. Don't drop 5 figures on a HVAC system then not be comfortable. I'd rather have a base 80% furnace with a 13 SEER A/C and nice zone control system than a 95% furnace/18 SEER A/C with poor ductwork design.

    Not only will the comfort be better, but your utility bills will be lower since you won't be overheating/overcooling one floor to make the others comfortable. Without zoning or multiple systems that's what typically happens in multi floor homes. Overheating/cooling floors will cost you WAY more than the 15% you save in gas by going to a 95% furnace.

  6. #6
    Join Date
    Dec 2012
    Location
    Sagamore Hills, OH 44067
    Posts
    8
    Well, I can't access my profile or attachments due to account restrictions. Maybe the message will help?

    GobyOneGnoby, you do not have permission to access this page. This could be due to one of several reasons:

    1. Your user account may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
    2. If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.
    We're in NE Ohio or zip code 44067. As for the ducts, they are what they are as it's a 50 year old house with most of the duct work inaccessible. Sorry, forgot to mention these are replacement units.

    I'll try attaching the report again, but here's the report summary just in case.

    Design Conditions: Cleveland
    Summer temperature: 73 Indoors, 88 Outdoors
    Winter temperature: 68 Indoors, 5 Outdoors
    Relative humidity: 50
    Summer grains of moisture: 94
    Daily temperature range: Medium
    Sensible Heat Gain 23,430 BTU/H
    Latent Heat Gain: 2,111 BTU/H
    Total Heat Gain: 25,541
    Total Heat Loss: 50,880

    Windows would reduce heat loss another 2,000 BTU/H and reduce total heat gain by almost 1,000 BTU/H.

    House Manual J Detail_12-20 Final.pdf

  7. #7
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,215
    2 ton AC and 60K furnace by your calculations...
    60k just seems like a LOT of heat for 1,600sqft...

    What size do you have now and how well do they heat/cool?

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,273
    Calculation seems Reasonable with the care you took to match your house.
    One might say heat load could be Slightly high.

    Infiltration is always the questionable variable.
    0.84 ACH winter is a fit for 50 year old house.

    2.5 ton Heat Pump with modulating furnace with switchover about 35'F.
    I would compare / review BRYANT products.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  9. #9
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,215
    Why the 1/2 ton oversize by everybody?

  10. #10
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    His location along with his Man J calcs would get a 2.5 vote from me as well. Being in the area I feel that the design temp is low from past experience.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,079
    His heat gain is 25,500 as is. The 13AJN, for example, is 23,000 BTU. I never liked cutting thing close. Have company over or do some extra cooling on a 90 degree day and it gets a bit warm in there. If he does good windows and drops his gain a bit and doesn't mind cutting it close, great. I just didn't want to risk customer complaints.

  12. #12
    Join Date
    Dec 2012
    Location
    Sagamore Hills, OH 44067
    Posts
    8
    Quote Originally Posted by 54regcab View Post
    What size do you have now and how well do they heat/cool?
    The furnace is an 80% 100K and the AC is a 3 ton. Both are 16 year old Goodman units, but they keep the house comfortable even in the coldest/hottest days. We've done a lot to the house to improve things (doors, some window and insulation), but they seem to be overkill at least for how the house stands now.

  13. #13
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    I would be comfortable going with the 60,000 furnace for your area given the age of your home and size unless there are extreme exposure issues. The wind does blow hard in the lake area.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


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