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  1. #1

    Help with New Central AC System

    We live in New England (RI) in a single level ranch house that is almost 50 years old. Outside dimensions are 50' x 26‘. We added attic insulation and replaced all windows last year. We have hot water baseboard heating and are looking to install a new central AC system: vents and air handler in the attic, ceiling diffusers, one zone thermostat, and single return in the main hallway.
    We received multiple estimates from three HVAC contactors. All contractors measured every room and mentioned that they would do a Manual J calculation. There are many options and we hope to get some of our questions (listed below these options) answered on this forum in order to help us select a system.

    Contractor 1: American Standard equipment
    Gold Series XM air handler 2.5 ton
    Gold Series SI Allegiance 13 SEER condenser 2.5 ton
    Or
    Upgrade air handler only to:
    Platinum Series XV variable speed air handler 2..5 ton
    or
    Upgrade both air handler and condenser to:
    Platinum Series XV variable speed air handler 2.5 ton
    Gold Series XI Allegiance 15 SEER condenser 2.5 ton

    Contractor 2: Lennox equipment
    Elite Series XC 13 SEER condenser 2.5 ton
    Elite Series CBX27UH air handler 2.5 ton

    Contractor 3: Carrier equipment

    This contractor gave 7 options (good “Comfort Series”, better “Performance Series”, best “Infinity Series”), but I’ve listed only the Infinity Series option.

    Infinity Series 16 SEER condenser single stage 2.5 ton
    Infinity Series variable speed air handler 2.5 ton
    Or
    Infinity Series 17 SEER condenser two-stage 2 ton
    Infinity Series variable speed air handler 2 ton
    Or
    Infinity Series 17 SEER condenser two-stage 3 ton
    Infinity Series variable speed air handler 3 ton
    (2.5 ton two-stage is not available)

    Do we need a high efficiency system with 2-stage condenser and variable speed handler?

    Some considerations:
    Summers in New England although relatively short, can have multiple hot and humid days.
    All three contractors agree that our house is at the upper limit of a 2.5 ton system.
    The house is covered by a lot of shade from trees, and we might cut many of these down in the future.

    One of these contractors recommends against a diffuser in the bathroom (11’ x 5’), but the other guys would put a small one there. The bathroom already has a new exhaust fan in the ceiling, with a timer. We’re leaning towards omitting it. What do you think? Thank you!

  2. #2
    Join Date
    Oct 2009
    Location
    God's country - Shenandoah Valley, VA
    Posts
    355
    Quote Originally Posted by Chase M View Post
    What do you think? Thank you!
    I think that I would be looking at a ductless mini split system instead. 30% more efficient and better comfort control.

  3. #3
    Join Date
    Jan 2008
    Posts
    2,023
    2.5 tons on 1300 sq ft in New England sounds a bit over sized.
    "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

  4. #4
    Join Date
    Oct 2009
    Location
    God's country - Shenandoah Valley, VA
    Posts
    355
    Quote Originally Posted by 2old2rock View Post
    2.5 tons on 1300 sq ft in New England sounds a bit over sized.
    Agreed.

  5. #5
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,156
    Yea, I wouldn't think your house being at the top of a 2.5 ton! We're a lot hotter with lots longer summer, 2 ton isn't unusual in a decently built house of that size.

    With shorter summer, going super SEER, say above 14, is likely to not provide any ROI. In other words, you are paying for savings you likely won't save. Something to think about.

    Yes, a mini is more efficient but hard to cool a whole house with one. Buying multiple would be rather salty! We did a 3 head Mistubishi this spring, ouch $$$. But we had no attic to run ducts in.

  6. #6
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,837
    The first issue you need to resolve is to let all 3 contractors know that you're considering their proposal but cannot agree to the installation unless they provide you with a printed result of the load analysis. You said they all measured but didn't say any of them actually did the load analysis or proved that they have done it.

    In Rhode Island, there is a program called CoolSmart. I'd visit their website and see if any of the 3 are contractors participating in that program. CoolSmart contractors receive annual training, part of which is properly sizing the equipment based on Manual 'S' calculations. Also, since you're starting from scratch, you'll want a CoolSmart trained contractor charging the system after the installation. Using CoolSmart, you'll also have a contractor who designs to lower static pressures and thus provides quieter and more efficient installations. Not saying they'll be the lowest installed cost mind you but quality costs. With CoolSmart contractors, you're removing a whole lot of guessing from the equation. Check it out.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  7. #7
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,985
    IMO,you're throwing money away if you go higher than a 14-SEER; forget the two stage stuff, & I'd under-size a little for longer runtimes & better humidity control.

    Your cooling seasons are too short to put extra needless money in cooling equipment.

    Also, get a low cost programmable room TH with a SWING setting so U can set it for longer runtimes & off times; that helps improve SEER performance without paying extra for it. Helps on heating too.

    Put the equipment savings into making your home more energy efficient, as that will save money during the short cooling period & the long months of the higher cost heating season in RI.

    Of course, if U have money & want the extras - by all means go all out for anything & everything U want; for some of us it's like the car you love & are proud of, - you want what U want!
    Last edited by udarrell; 07-14-2012 at 05:29 PM. Reason: Or, go for all of it...

  8. #8
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,692
    A lot of good advice from all. I would also recommend asking for a layout of the duct system with the register sizes and locations.

    Also, it should include the ductwork sizes and how they will be installed.

    If you have easy access to the AH I would recommend a large 4-5" hi-eff. filter installed.

    This helps with airflow, sound, they don't need replacing as often and they will capture more dust.

  9. #9
    Thanks for all the responses so far! We'll be sure to ask for the printed load analysis and we'll check out CoolSmart.

    udarrel: On the idea of longer run times for better humidity control -- the impression we got from more than one contractor is that we should use a multiple/variable speed air handler to get that effect (instead of going under-sized or using a single speed AH).

    BaldLoonie: We asked one of the contractors why he proposed higher SEER systems given that we won't be handling as many hot days as, say Florida... (and thus little or no ROI)...He showed us the math on the higher rebates that come with the more efficient systems. In our case higher SEER doesn't necessarily mean significantly higher cost.

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