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  1. #1
    Join Date
    Aug 2012
    Posts
    6

    Is it big enough?

    We're looking at a house we'd like to buy, but I'm concerned the HVAC may not be adequate. I realize there are a ton (no pun intended) of variables in sizing a system, but I'd like to give a description of the house and system and see what folks think the likelihood is of this being a problem situation.

    The house is about 90 percent renovated, with a brand new never used Amana (Goodman) 13 SEER 5-ton compressor, and a matching gas furnace (same brand/capacity). This being a renovation, the system has never actually been used.

    The house is HUGE. It is well over 3000 sq ft upstairs, and there is about 2500 sq ft downstairs that is finished. The upstairs is mainly 8 foot ceilings, but the is a 9 or 10 foot ceiling in the kitchen/LR, and another tall ceiling in the master BR and bath. There are no 2-story rooms in the house. The downstairs is all 8-foot ceilings.

    The single 5-ton unit has been installed to service both upstairs and downstairs.

    Knowing what little I do about HVAC (I'm in the middle of my first HVAC class), it seems like this system *might* be sufficient for the upstairs, but I can't see how it could service both upstairs and downstairs. Even if it has the capacity, it seems that balancing would be a problem as the seasons change. I don't know how to compare a 13 SEER system to to the 10 SEER (and lower) systems I'm more familiar with, so I don't know if the 13 has some magic that would make it work in this situation.

    I realize it's impossible to give an accurate answer without seeing the house and taking measurements, but can I get some feedback on whether this house is something I should consider, or whether I should walk away from it as a disaster waiting to happen?

    Thanks

  2. #2
    Join Date
    Oct 2012
    Location
    Toronto, Ontario
    Posts
    67
    is the basement underground? how tight is it may not have to take into consideration 5 ton should be good from anywere from 4700- 5300 sq ft

  3. #3
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,667
    Quote Originally Posted by Steveo86 View Post
    is the basement underground? how tight is it may not have to take into consideration 5 ton should be good from anywere from 4700- 5300 sq ft
    1000+ sq ft/ton is usually adequate for a tight, well insulated house. Does it have an automatic zone system or manual dampers, if zoning is done properly you will have a 1-3F temp difference between down and up. If done wrong it could be 5-15+ temp difference.

  4. #4
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,022
    The climate area you are located in can make a big difference...where?

    The new higher SEER condensers use smaller Btuh capacity compressors compared to the tonnage Ratings,therefore, under some tough conditions they may not move as much Btuh heat to the outdoors as the old lower SEER colder evaporator coil units...

    If there has not been a Home Energy Efficiency Audit or Rating performed I'd have one done.

    Of course, there should be a room by room heat-gain heat loss load calc performed; then a manual D to see how the duct system & airflow stacks up with actual requirements.

    I'd get as much guesswork out of the heating & cooling equations as possible; - know what you're buying.

  5. #5
    Join Date
    Aug 2012
    Posts
    6
    Thanks for the info so far, it has been helpful. This is a house in GA, north of Atlanta. Summers always get into the 90's with high humidity, usually hitting 100 for a few days each year. Winters are not so bad, but usually get into the 20's for several days.

  6. #6
    Join Date
    May 2008
    Location
    Central Fla.
    Posts
    311
    You could have a remote sensor in the "other zone" from where the thermostat is located(up or down don't know where your tstat is located) and have an averaging thermostat put in . Almost like having 2 controllers.It will get you as close to having 2 controller as you can without zoning.

  7. #7
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    It just depends on the construction. I can cool my 3200sqft house with 3.5-4 tons, and it has minimal insulation and lots of windows, but moderately tight and good shading. A well insulated new construction, that's zoned could be doen with 5 tons.

    Atlanta, beleive it or not, is actually 1F cooler is dry bulb and wet bulb temepratures than where I an in SE Iowa. Design I think is 9F, 76F wet bulb.

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