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  1. #1
    Join Date
    Jul 2013
    Posts
    6

    Adding AC to a 1970's bi-level home

    I'm in northern NJ, here are some basics on the home:

    Original forced air furnace with no AC.
    "energy efficient" windows installed ~5 years ago.
    2100 sq/ft home

    After being miserable in the heat wave we just had, I figured I would look into adding AC. This isn't as easy as it seems!

    My first quote was very vague. He would swap the furnace, add a coil on top and install a 4 ton condenser outside. He seemed to like using Goodman products; GMH8100, ZAPF4860C, and GSX1348 respectively.

    The second totally took me by surprise. He wanted nothing to do with adding a coil above the furnace and was adamant about installing everything in the attic and running duct to the upstairs rooms. The two bedrooms downstairs would need a duct run down an upstairs wall (which are brand new from the kitchen remodel I'm wrapping up) but could at least be done at a later date. No word on price or specific products, he was going to work up a list. We were also talking about a furnace swap and variable speed units and so on, just that I would need a 3.5 ton unit.

    I do have the usual drastic temp difference that comes with this style home. I think that the second option might be the way to go, but I'm not sure. I bet it will be way more expensive, but I would like a comfortable home.

    Would the attic install be the correct way to cool my home? I have talked to no one who has even hinted about doing a heat loss calc or anything similar to that. I am aware of the program you can buy, but I think the 2 month lifespan is a little silly.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,043
    Sounds like you need to keep looking for a good contractor. At a guess, 3.5 to 4 tons for 2100 sq ft in Joisey seems excessive. Could end up cool but damp.

    Is there not runs to all the rooms on the 2nd level now?

  3. #3
    Join Date
    Jul 2013
    Posts
    6
    I guess so. Why would it end up damp?

    There are vents in all rooms up and down for the forced air, but they are all down low... not beneficial for cooling.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,043
    Oversized A/Cs short cycle, running only a few minutes at a time, especially in milder weather. On many systems it can take over 10 minutes of running to reach dehumidifcation levels. If you have a big unit not running a lot, it will cool but not remove moisture leaving the space rather damp.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Oversized units cool the temp down too fast. So hey don't run long enough to remove enough moisture. So you end up with high humidity.
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  6. #6
    Join Date
    Jul 2013
    Posts
    6
    Ok thanks for the explanation.

    Which method is the norm for adding AC to a home like this? I dont want to be taken for a ride, nor do I want to drop 6-8k on a system that will not give me what I want.

    I think I should at least do or have a heat loss calc done to get the correct sized equipment and keep getting quotes.

  7. #7
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,626
    Omega..........when you say a 2,100 sq. ft. bi-level home, I picture a split foyer. Is part of the 2,100 sq. ft. partially underground?

  8. #8
    Join Date
    Jul 2013
    Posts
    6
    Walk in front door to landing. Up is kitchen/dining/living/3 bedrooms and a bath. Down is family/2 bedrooms and another bath. Was my terminology wrong?

  9. #9
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,043
    No, you have what I pictured. Tell your dealers you won't buy from them without seeing a heat gain calc justifying the big A/C.

  10. #10
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,626
    Quote Originally Posted by OmegaWS6 View Post
    Walk in front door to landing. Up is kitchen/dining/living/3 bedrooms and a bath. Down is family/2 bedrooms and another bath. Was my terminology wrong?
    We call it a split foyer in my neck of the woods. My point is to better understand the A/C requirements. If the home has 1,050 sq. ft. up and the same down, the A/C size should be closer to 2-2.5 tons.

    Does your home have a walk out lower level? Is the garage attached?

  11. #11
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,271
    800 Cooling Degree Days
    5200 Heating Degree Days
    So, the xx degree days tell you the Relative importance

    It's difficult-to-impossible to imagine what the original duct work for the furnace is and
    whether it's close to adequate for a 3 or 3.5 ton A/C unit.

    http://www.climate-zone.com/climate/...-city-airport/
    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

  12. #12
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,626
    Quote Originally Posted by dan sw fl View Post
    800 Cooling Degree Days
    5200 Heating Degree Days
    So, the xx degree days tell you the Relative importance

    It's difficult-to-impossible to imagine what the original duct work for the furnace is and
    whether it's close to adequate for a 3 or 3.5 ton A/C unit.

    http://www.climate-zone.com/climate/...-city-airport/
    I hope that you meant to say hours...........or you year has more days than mine.............lol.

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Quote Originally Posted by George2 View Post
    I hope that you meant to say hours...........or you year has more days than mine.............lol.
    He meant days. It doesn't refer to the actual amount of days in a year.

    1 heating degree day is 64 degrees for 24 hours. Each additional degree under 65 for 24 hours is an additional heating degree day.

    Check out Manual J.
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