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  1. #1
    Join Date
    Nov 2005
    Location
    Livingston, NJ
    Posts
    16
    We are planning to replace the furnace and AC which are both over 30 years old. Our house is a two-story colonial with about 3,200 sq feet in size.

    The heating is mostly ok. But AC wasn't adequate in summer: it took forever the drop even one degree in temperature. What's worse is that the second floor was too hot most of the time.

    One contractor said that a single-zone AC will always be a problem in a house this size. (And it faces West.) Is this true?

    In the meantime, another contractor said today's variable speed furnace reaches further in the house and the second floor won't be a problem.

    We have decided to put in a variable-speed furnace but have a tough decision to make on the AC. Should we make a straight replacement or put in a smaller unit and add another unit in the attic (plus the duct work) just for the second floor to make it a two-zone?

    Ultimately two-zone AC will be more comfortable but the cost is much higher. We are not sure what to do. Any advice?
    Thanks!!

    Dennis




  2. #2
    Join Date
    Apr 2005
    Location
    NE PA
    Posts
    698
    I always recommend 2 zones in a 2 story where practical. Load balance and comfort are much better, especially if you live in a seasonally hot and cold area. You will also find that the operating costs are somewhat lower due to better load matching. Unfortunately the operating cost savings will never offset the installation costs.

    paul

  3. #3
    Join Date
    Nov 2005
    Location
    Livingston, NJ
    Posts
    16
    Agreed. The installation cost is the key here. So our wishful thinking is that we could still be comfortable with just one-zone.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    It comes down to how much is your comfort worth to you.

    A VS blower will help, but it won't make it the same as 2 systems.
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  5. #5
    Join Date
    Nov 2005
    Location
    Livingston, NJ
    Posts
    16
    Another concern is the noise made by the second unit. Would we hear it from the attic?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    That will depend on how good your contractor is.

    For the most part, no.
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  7. #7
    Join Date
    Nov 2005
    Location
    Livingston, NJ
    Posts
    16
    The bottom line is whether or not a single zone AC can be sufficient for the house. If yes, we'll probably save the money and not put in the second zone. Did anyone face the same issue before?

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    A single zone system will never keep both floors at the same temp.

    We've installe alot of 2 system jobs, and zoned jobs because of this.

    None have ever had buyers remorse.
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  9. #9
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,243

    Temperature ZONING

    Originally posted by dc00
    Another concern is the noise made by the second unit. Would we hear it from the attic?
    A Second ZONE does not necessarily require a Second A/C system. Temperature zoning uses dampers and controls.
    i.e.
    http://www.arzelzoning.com/whatiszoning.html

    Area zoning is done by adding another piece of equipment.

    However, 3,200 Sq. Ft is a 'lot to ask of' one 5-ton system.

    Location: ____ City State
    House
    Dimensions .......# Windows
    West ____ft[~48 ].. 7 ?
    South ___ft[~32 ].. 4
    East ____ft[~48 ].. 7
    North ___ft[~32 ].. 4

    < just for starters:

    [Edited by dan sw fl on 12-03-2005 at 07:30 AM]
    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

  10. #10
    Join Date
    Nov 2005
    Location
    Houston
    Posts
    51

    Arzel Zoning!

    I agree with Dan. Make sure the company you choose has the proper experience if you go with a damper zoning system. We see a lot of wana-bees in the residential zone business here in Houston. Stay away from the low bidder!
    Joe Watkins
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  11. #11
    Join Date
    Nov 2005
    Location
    Livingston, NJ
    Posts
    16
    We don't need two floors to have the same temperature. All we want is to cool down the 2nd floor sufficiently so we can sleep comfortablely in the evening on a hot summer night. We don't mind closing all the registers on the first floor. Can a 5-ton AC plus, say, a Carrier Infinity furnace handle this?

  12. #12
    you cannot keep the second story of a home comfortable with one system. hence your problem. variable speed furnaces are good but will not correct your problem.
    i would have a heat load calculated to see if a 5 ton system with a 2 zone zoning system will work. if not you will have to go two systems. with the size of your home probably 2 systems.

  13. #13
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    If you close all the down stairs regs, you'll do more harm to your a/c then good.

    End up costing you more in repairs, then what the second system will cost.
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