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  1. #1

    2 HVAC system v 1 HVAC System

    I have a new two story home of approx. 2800 sq.ft in South Jersey under construction. We have a choice of two hvac systems one for each floor with separate supply and return trunks in the basement. One is 60,000 BTU and the other is 80,000. The other choice is a single 100,000 BTU with split supply zones and one return truck to which all return ducts are attached with a bypass damper. One zone is the 2nd floor and other is the first floor with electronically controlled dampers operated by the thermostat on each floor. Which system is a better quality for control, comfort, efficiency and maintenance? Thank you

  2. #2
    Join Date
    Jan 2008
    Posts
    2,117
    2 systems would be the best way to go. And they need to be sized properly. Zoning can be a good alternative, but if it's not done right , it will be a nightmare.
    Looks like you contractor is oversizing. Not good.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,587
    2 systems! And ditto on the size. If 100K single unit would do it, 2 units totaling 100K would do it. I sure don't know what they are thinking!

  4. #4
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Well insulated new construction in Jersey, that sounds like a LOT of heating for that size place. 140k BTU if sized correctly = $500 heating bill in winter.

    You should be able to heat the whle place with 80k BTU if it's constructed well. I'd go 2 systems, but if 100k will heat the whole place then you should only need a 45k upstairs and 60k downstairs. Two 2 ton AC systems should be plenty as well. 4 tons of cooling would = a electric bill of around $250-300 in summer depending on your base use and electric rates.

    Get load calculatoins done. New Jersey doesn;t have Houston summers or Minnesota winter.... heck, 140k BTU would be a lot even if this place was in Alaska with a -20F design temp.


    Properly sized = comfortable, even temerpature, much lower cooling bills, quiet, less draft, lower installation costs.

  5. #5
    Thank you

  6. #6
    Join Date
    Oct 2004
    Location
    So Cal
    Posts
    3,603
    2 systems is the best way to handle 2 story.

  7. #7
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,500
    Quote Originally Posted by motoguy128 View Post
    Well insulated new construction in Jersey, that sounds like a LOT of heating for that size place. 140k BTU if sized correctly = $500 heating bill in winter.

    You should be able to heat the whle place with 80k BTU if it's constructed well. I'd go 2 systems, but if 100k will heat the whole place then you should only need a 45k upstairs and 60k downstairs. Two 2 ton AC systems should be plenty as well. 4 tons of cooling would = a electric bill of around $250-300 in summer depending on your base use and electric rates.

    Get load calculatoins done. New Jersey doesn;t have Houston summers or Minnesota winter.... heck, 140k BTU would be a lot even if this place was in Alaska with a -20F design temp.


    Properly sized = comfortable, even temerpature, much lower cooling bills, quiet, less draft, lower installation costs.
    I'd split the A/C 2.5 tons upstairs, 1.5 downstairs instead of 2 tons each floor. Even in Oklahoma 1 ton per 1,000 sq ft is typically enough for downstairs units.

  8. #8
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Depends on the load calculation and home construction. Downstairs might have more windows in a modern neo-ecclectic (cluttered hodgebodge of shapes) home. Upstairs could have more shading or deep soffits and downstairs has more load from appliances, Occupancy.

    But all things being equal, your right, upstairs is better off a little larger than downstairs. This home might only need 2 tons up 1.5 tons down.

  9. #9
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,500
    You would almost have to go out of your way to make the downstairs have a higher cooling load per sq ft than upstairs. In the real world you're looking at close to a 2:1 ratio per sq ft, if not more. Same for heating, you would have to go out of your way (or bury part of the downstairs underground) to make the upstairs have a higher heat load than downstairs. If the house is well insulated you may not ANY heat upstairs in moderate climates. Most heat needed for upstairs will simply float up from downstairs...

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