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  1. #1

    Selecting a New Furnace

    Hello,

    I am a first-time home owner who is trying to figure out what to do about replacing a 40-year-old furnace. I have the following 3 bids:

    Lennox G43UF-36C-090
    88,000 BTU
    92.1% AFUE
    Option to step up to either:
    G61MP-48C-090
    88,000 BTU
    92.7% AFUE

    G61MPV-36C-090
    79,000 BTU
    94.3% AFUE

    Lennox G51MP-36B-070
    62,000 BTU
    92.1% AFUE
    Option to step up to:
    G61MP-36B-070
    62,000 BTU
    94.1% AFUE

    Heil (Model not listed in bid)
    100,000 BTU
    92.2% AFUE


    I found a site that has a sizing estimator My house is about 1800 sq. ft., with about half of that being a full basement. The sizing estimator instructs users to not include basements, so I entered my square feet as 950 (the ground floor is slightly larger than the basement). The estimator also requires a zip code (I live in Helena, Montana). Based on my input, the sizing estimator calculated that I will need only 37,000 BTUs.

    Here are my questions:

    1) I'm not sure if that sizing estimator is reliable. Without getting into all the work of doing a Manual J load calculation, what is the best way to estimate the BTUs that will be sufficient to heat my house?

    2) I know that the higher the AFUE, the more efficient the furnace and the more money that will be saved on my heating bill. But I'm really debating between a model in the 92% range and one in the 95% range. I haven't been able to find any information to tell me if the additional 3% will result in enough cost savings on my heating bill to offset the greater cost of the 95% AFUE furnace. What kind of additional annual savings could I expect with the 95% furnace over and above the 92% furnace?

    3) Can anyone tell me which of the furnace models list above has the best reliability track record?

    4) Can anyone recommend other furnace makes and models that are highly reliable? How about 95% furnaces (Since none list above are 95%)?

    Thanks for any help that you can offer!

    --Tom
    Last edited by Senior Tech; 09-03-2008 at 07:35 AM.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,717
    Edit out that web site. Its a DIY site. Not allowed to be posted here. Thank you.

    Going from a 92 to a 95%, saves you 3 bucks on the hundred.

    The basement is included if its heated, and is seldom more then half the load of the first floor.

    Without doing an accurate Manual J, no way to know what size you need.
    A load calc also takes into consideration where the ducts are loacted.

    The MVP is a nice unit.

    Call caontractors that carry other brands, and see what they recomend.
    Most brands have 95% models.
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  3. #3
    Thanks for the information!

    Your reply has made me think of two more questions. Hope you don't mind.

    1) I had three contractors come in and do bids for no charge. All of them did a fairly quick walk-through, asked about square footage and insulation, and looked at the existing ducts. Each contractor was there for 30-45 minutes. My impression after reading about Manual J calculations is that there is a lot of detail that goes into them, and that they would require a fair amount of time. Am I wrong about that? Is an accurate Manual J something that a competent contractor could do in a 45-minute walk through? I seem to remember reading that not all contractors do Manual J. Is that something I would have to ask for specifically, and is there generally a charge for having a Manual J done?

    2) Without respect to brand, are there any furnace design features that I should try to avoid? Are there any features, aside from things like efficiency, that are particularly good to have?

    Thanks again for your help!

    --Tom

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,717
    VS blower if your in a humid area.

    Yes, you will have to ask them if they even do Load calcs. Many don't.
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  5. #5
    Join Date
    Aug 2008
    Posts
    27

    No different

    Quote Originally Posted by Thomasm516 View Post
    Thanks for the information!

    Your reply has made me think of two more questions. Hope you don't mind.

    1) I had three contractors come in and do bids for no charge. All of them did a fairly quick walk-through, asked about square footage and insulation, and looked at the existing ducts. Each contractor was there for 30-45 minutes. My impression after reading about Manual J calculations is that there is a lot of detail that goes into them, and that they would require a fair amount of time. Am I wrong about that? Is an accurate Manual J something that a competent contractor could do in a 45-minute walk through? I seem to remember reading that not all contractors do Manual J. Is that something I would have to ask for specifically, and is there generally a charge for having a Manual J done?

    2) Without respect to brand, are there any furnace design features that I should try to avoid? Are there any features, aside from things like efficiency, that are particularly good to have?

    Thanks again for your help!

    --Tom

    That is no different at all to my est guys,some stay 15 min and 2 stay 2 hrs do all the windows size and sit down for calc, at the end they all come up the same BTU and model number furnaces and brand, but different prices, I pick the lagers local gas company and ask them to match and bid the price.
    Since we all know most of the dealer is trained by the manufacture, they should know the products and installation. why so much different in prices, I got as high as 80% more for the same thing, so I believe if the lower price contractor still make money for all the work, the HVAC business have a lot of room to move on pricing. I am happy on my new Lennox G71P and XC14 AC, it also saved me a lot of money.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,717
    You might be supprised how many don't send their techs to factory training.
    And really are not up on what all the unit they are selling can and can not do.
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    How many times must one fix something before it is fixed?

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