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  1. #1
    Join Date
    Jul 2011
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    71

    Question about Furnace Selection

    My sales guy was here tonight. Could use some advice from the experts. He quoted me three 80,000BTU systems.

    1.) Bryant 359AAV. 95% AFUE.: Baseline cost.

    2.) Bryant 355BAV. 95% AFUE + DC Motor + 2-Stage Heat : Costs 33% more than Option 1.

    3.) Bryant 355CAV. 95% AFUE Evolution. : Costs 44% more than Option 1.

    Evolution has too many bells and whistles and my AC unit cannot take advantage of some of the features it offers so OPTION 3 is OUT.

    Questions:
    1.) Is the DC motor and 2-stage operation (option 2) worth the 33% premium. Those are the two features that stand out to me and sound nice.

    2.) Should I be trying to find a lower efficiency unit that has the 2-stage operation and DC motor (i.e. are 80% units a lot less expensive)?

    Gas is cheap around here. Going from 80%-95% will only save me $118 per year.

    To complicate the matter, my gas company gives me a $460 rebate for getting a 95%+ efficiency furnace.

    Thanks,
    Clocker

  2. #2
    Join Date
    Aug 2011
    Posts
    568

    Arrow

    Quote Originally Posted by Clocker View Post
    My sales guy was here tonight. Could use some advice from the experts. He quoted me three 80,000BTU systems.

    1.) Bryant 359AAV. 95% AFUE.: Baseline cost.

    2.) Bryant 355BAV. 95% AFUE + DC Motor + 2-Stage Heat : Costs 33% more than Option 1.

    3.) Bryant 355CAV. 95% AFUE Evolution. : Costs 44% more than Option 1.

    Evolution has too many bells and whistles and my AC unit cannot take advantage of some of the features it offers so OPTION 3 is OUT.

    Questions:
    1.) Is the DC motor and 2-stage operation (option 2) worth the 33% premium. Those are the two features that stand out to me and sound nice.

    2.) Should I be trying to find a lower efficiency unit that has the 2-stage operation and DC motor (i.e. are 80% units a lot less expensive)?

    Gas is cheap around here. Going from 80%-95% will only save me $118 per year.

    To complicate the matter, my gas company gives me a $460 rebate for getting a 95%+ efficiency furnace.

    Thanks,
    Clocker
    go with # 2 the high efficency motor uses about 1/2 the electic as a standard motor!

  3. #3
    Join Date
    Jul 2011
    Posts
    71
    Definitely the way I am leaning. However, can I find the same system as #2 but with 80% AFUE for a much lower cost?

  4. #4
    Join Date
    Aug 2011
    Posts
    568

    Confused

    Quote Originally Posted by Clocker View Post
    Definitely the way I am leaning. However, can I find the same system as #2 but with 80% AFUE for a much lower cost?
    me personally, if you don't have a problem with clearences why would anyone go with a 80%. it's better for envirement,saving valuble resources,saves on energy,less polutants,etc. just my opinion, good luck.

  5. #5
    Join Date
    Sep 2002
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    2,903
    Gas is cheap now, but it won't be forever.

    80% AFUE units pull combustion air from inside the house, increasing the need for humidification.

    Even at $118 per year the roi is better than what you would get any stock or bond investment on earth. The payback over an 80% eff unit is around five years - less if it saves you from having to run a humidifier.

    I would go for option #2 - make sure that the contractor connects the combustion air intake and uses a 2-stage t-stat. Don't let them cripple a several thousand dollar furnace to save a couple hundred bucks on materials and labour.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,741
    Have a load calc done, and find out if you really need a 80,000 BTU furnace. may be that you only need a 60,000 BTU furnace.

    A 80,000 BTU 95% furnace needs to move more air then a 80,000 80% does. Your duct system may not be big enough for a 80,000 95%. And could cause you to use more gas.
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  7. #7
    Join Date
    Jul 2011
    Posts
    71
    Good point about the load calc. I forgot to ask about that although I told the sales guy I was happy with the heating performance on my current 80000/80% system. If I go with the 80000/95% system it'll have about 5000 BTU more max capacity. If I go down to a 60000/95% system, I will end up losing about 14,000 BTU max output though so I think that might be too much to lose. We'll see though.

    With respect to airflow, I looked up the specs. on my current (395CAV) furnace vs. the 355BAV.

    Old Bryant 395CAV 80%:
    Heating airflow 1,170CFM


    Bryant 355BAV 95%:
    Heating Airflow Low: 860CFM
    Heating Airflow High: 1245CFM

    The 75CFM difference on high (6.4% increase) with the new system seems negligible to me. I guess I could just open a couple vents I currently have closed in the house to balance that out?

  8. #8
    Join Date
    Jul 2011
    Posts
    71
    Quote Originally Posted by amd View Post
    make sure that the contractor connects the combustion air intake and uses a 2-stage t-stat. Don't let them cripple a several thousand dollar furnace to save a couple hundred bucks on materials and labour.
    I talked to the sales guy about T-stats. I currently have a LuxPro 2-stage T-stat (even though my current furnace is single stage). I replaced the old one I had with the LuxPro because I wanted something that had more swing adjustment.

    Nonetheless, the sales guy told me that the stages in the furnace are controlled by a sensor in the furnace that monitors the temp. of the incoming air and that they would not need to be controlled at the T-stat. Is it better to use the stage control via the T-stat?

  9. #9
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    Sep 2002
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    He lied to you in that case.

    Bryant/carrier furnaces time out after a maximum of 16 minutes when used with a single stage t-stat - often less if the previous cycle was long. They also do not switch to low after running on high.

    You need to find a new contractor.

    If pulling a new wire isn't practical, request "add-a-wire" - an inexpensive product which allows you to use a 2-stage t-stat on a 4 conductor cable.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  10. #10
    Join Date
    Sep 2002
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    I don't know
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    2,903
    What kind of house do you have?

    A new 80k 95% unit puts out nearly as much heat as a 100k mid efficiency furnace; a 60k 95% unit puts out as much heat as a 75k mid eff unit. (commonly seen in well insulated houses up to 2500 sq ft or so - but don't take my word for it)

    Don't oversize if unsure - get a load calc done or do it yourself.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  11. #11
    Join Date
    Jul 2011
    Posts
    71
    I would not say he lied. He told me they could install it any way I like, either using my T-stat or the internal furnace control. I think most HO's don't want to mess with different settings on the T-stat to much so they default to the internal control.

    Working on the load calc. right now with guidance from my contractor.

    Since it's 2-stage, wouldn't it be somewhat better to be on the big side rather than small so the furnace can stay in the quieter 1st stage more? I can see being on the smaller side with my AC since it doesn't have multiple stages per se but I'm not sure about the furnace. If I drop down to the 60K BTU, even at 95% I am 14K BTU less than my current furnace.

    My house is a 2100 sq. ft. ranch with vaulted ceilings and lots of big crappy leaky windows that I should replace. Built in '94. Sits on a basement that I have partially finished. Located in SE Michigan. This calculator does indeed indicate I am slightly undersized with my Air and Furnace (but I DID read the fine print).

    http://www.hvacopcost.com/equipsize.html

    Certainly no expert here...just thinking out loud & trying to learn.

  12. #12
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    Sep 2002
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    Since it's 2-stage, wouldn't it be somewhat better to be on the big side rather than small so the furnace can stay in the quieter 1st stage more? I can see being on the smaller side with my AC since it doesn't have multiple stages per se but I'm not sure about the furnace. If I drop down to the 60K BTU, even at 95% I am 14K BTU less than my current furnace.
    No - smaller is better provided that it can keep up.

    A good t-stage stat (not sure about the lux) will run on high only when required; if the heat loss is marginally above the output on low, it will run in high just enough to maintain the setpoint.

    The 80k unit on low provides almost as much heat as the 60k unit on high, so it won't be quieter anyway.

    When it comes to load calcs, garbage in = garbage out.

    Window frames can leak more than the windows themselfs; if it's very drafty, caulk around the trim. (removing the trim and spray foaming is an option, but it's probably labour intensive + expensive) Removable caulk is available for operable windows.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  13. #13
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,843
    Quote Originally Posted by Clocker View Post
    Old Bryant 395CAV 80%:
    Heating airflow 1,170CFM


    Bryant 355BAV 95%:
    Heating Airflow Low: 860CFM
    Heating Airflow High: 1245CFM

    The 75CFM difference on high (6.4% increase) with the new system seems negligible to me. I guess I could just open a couple vents I currently have closed in the house to balance that out?
    There is a world of difference between those furnaces, the newer one has an ecm motor and it will put out the air it says or die trying. Are you sure of the model #? It your current choice the 353BAV? There are many posters here that have had ecm motor replacements that now HAVE loud airflow
    Give a man a fish, he will eat for a day. Teach a man to fish, he will eat for a lifetime.

    Give a man a capacitor, doesn't know what to do. Teach a man to install it, now he knows everything.

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