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  1. #1

    Question Help! Am I being sold a system that is too big?

    Hello - I've spent a good chunk of time reading and perusing threads on here, and in just a few hours, feel so much more comfortable trying to understand the quotes I have for a new HVAC system. That said, I'm hoping a few of you can provide some insight into what I'm looking at.

    House: Denver (so 0 deg for winter, 92 for summer are the numbers I'm supposed to be shooting for, regardless of the fact it has been in the upper 90's for 2 weeks now ), 1-story, solid brick (built in 1911), ~1,000 sq feet main floor, basement that is 80% finished. New double-paned vinyl windows through entire 1st floor, a few older windows remain in the basement. 4" of insulation currently in the attic, which will be upped to 12" soon. Garage is detached, so no worries there.

    Replacing: There is currently no A/C, just central heat from a 35 year old furnace. I'll be adding in A/C and replacing the furnace.

    Quote 1 - Installer recommended 80,000 BTU Trane XV95. Load calculation done at 50,000BTU (assuming 12" insulation in the attic). According to him, I need an 80,000 BTU furnace because 80,000 * 95% (furnace) * 83% (altitude adjustment) is 63K BTU. My other option (which he says is priced almost exactly the same) is a 60,000 BTU Train XV95. The same calculation above brings that to only 47K BTU, which falls under the load calc of 50K. In addition, he recommended a high-efficiency Trane A/C unit, but I'm unsure of the model number.

    Quote 2 - Installer recommended 80,000 BTU 95% Armstrong furnace. I didn't get the detailed load calcs from him, so I can't compare directly. Also recommended a high-efficiency A/C unit.

    Both installers have all their qualifications. And I like both of them. The main difference seems to be Trane vs Armstrong, and the fact the Armstrong quote is about 30% less than the Trane. Granted, it seems Trane has a better track record, but I'm able to buy a 10 year P&L warranty on Armstrong for about the same price as I am with the Trane, so I'm wondering if there is any real downside to saving the 30%?

    Also, my concern is I've read SO many comments regarding how installers often want to sell you something bigger than you need, simply because they don't want you calling them because your unit can't handle the load in a cold snap. What kind of efficiency do I stand to lose by purchasing a slightly over-sized furnace? (I mean, it would be nice if the furnace could keep up during -10 degree cold snaps, but I'm trying to understand the loss in efficiency I'm paying for....) In your opinions, is an 80K furnace for what I'm describing (given the 50K load calc) way over-sized?

    Any other comments or advice would be welcomed as well. Thank you so much for your help.

    - Ulim

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,727
    The derate makes the 80,000 a good selection for your home.
    A 75,000 95% would only drop you to 58,000 BTU output.
    Not enough difference to worry about.

    What size A/C?
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  3. #3
    Quote Originally Posted by beenthere View Post
    The derate makes the 80,000 a good selection for your home.
    A 75,000 95% would only drop you to 58,000 BTU output.
    Not enough difference to worry about.

    What size A/C?
    Thank you.

    I'm being told I need 1.7 tons, so it would be a 2 ton system. If I remember right, there was a cheap option (XP13?), and then another 2-stage option, that cost about 50% more than the cheaper option. So I suppose a follow up question is whether it is worth it on the A/C to upgrade?

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,727
    I don't think so in high altitude areas.
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  5. #5
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,898
    How often does it hit zero? Personally I'd probably go the smaller and and potentially be a bit chilly a few mornings a year.

    The 80K furnace wants to move a lot of air. I'm wondering if 1000 sq ft home has a duct system that can move that much air. If not, it will be very noisy in there!!!

  6. #6
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,517
    I would go Trane. My opinion is you get what you pay for. Other than that, you deal with. The one question is your wife gonna like chilly mornings or does she like it warm like mine does. That will decide your sizing. Mine wants to be cold when she wants it cold and wants it warm when she wants it warm. When mama is happy. All are happy.

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