Is it worth it to go to a 95% furnace?


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I currently have TWO 80% 20 year old Tempstar 150K BTU furnaces, one for each floor in my 4600 sq ft home (2300 in each floor) (built in 1989).
Due to some situation, the builder will be replacing both furnaces with new Trane 92% furnaces. He says that per his calculations TWO 120K BTU furnaces will be enough for my home (I am adding R30 cellulose insulation to my attic)
I have to pay extra if I need TWO 95% furnaces instead and extra if I want TWO variable valve and variable speed ones (all from Trane)
I use $2288 worth of gas each year to heat my hone and operate the hot water heater and drier each year.
Questions:
1. Am I right that I will save 3% on my gas bill with the extra 3% efficiency? That means I will save $60 each year and for the lifetome of the 95% furnace which is 20 years, I will save $60X20=$1200 for both furnaces ($600 for each furnace). So anything more than $600 extra for each 95% furnace will not be cost effective
2. What is the gas savings with the variable valve and variable speed.
3. Do variable valve and speed furnaces make any sense financially and even comfortwise in a 2 furnace home?
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On Fri, 16 Oct 2009 20:19:19 +0000, kris60660_at_yahoo_dot snipped-for-privacy@foo.com (heartmd) wrote:

You didn't say where you live but unless you live in Nome AK you are probably oversized. What you need to do is run a manual J heat loss calc on your home. Size the furnace(s) accordingly and get the highest efficiency you can afford.
Emphasis on the following. You will be decreasing the input and using more of the output. Its a win win.
A properly sized two stage highest efficiency variable speed furnace is the way to go. A two stage variable speed furnace will modulate the output according to outside conditions thus minimizing input whenever possible. Do the math using your personal data and see what your costs compare to now. I think you'll find a much greater savings than you currently anticipate.
Tell the mormon to piss off.
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On Fri, 16 Oct 2009 19:01:37 -0400, The King

    Pretty close. Actually 2.xx something

    What would that money get you in a CD etc for 20 years ? Your loss of that benefit over time adds to your investment cost now, realized 20 years from now.
    IOW - do you want to wait around 20 years to get your 600 $ back, no interest ? If so, please send it to me today ;-)

    That's more a comfort issue ( evenness of temperature ) than fuel cost.

    Judgement call.

120,000 doesn't seem oversized for 2,300 sq ft ( per floor )

    Yes.
    Within, as he discusses, reasonable price / payback calculations. Within which he forgot to adjust for the time value of money. $ 600 today = $ 1,800 20 years from now, etc.
    IMO, the 92 might be the better deal. lots of variables, of course.

    The bitch never pays attention.
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On Fri, 16 Oct 2009 20:18:41 -0400, .p.jm.@see_my_sig_for_address.com wrote:

have to have 95% afue or better furnace. Like you say 3% isn't a huge deal but to me the best way to drive prices down is try and use as less as possible.
I try really hard at limiting my energy consumption. Insulation is cheap, ive saved a tank and a half of LP over a years time by adding insulation to the attic.. insulation. 300 lp savings 5-600. Its a no brainer.
It would make sense to first check and if necessary add insulation to decrease heat loss downsizing ever further. Insulation could save the equal amount, or nearly as much, as the 3% eff increase of a furnace.
The price difference is not that large between the two (92-95+) anyway. Just a few hundred. Might as well get the best bang cause the average guy is only doing this once or maybe, twice.
Lots of variables as you say.

He's punch drunk.
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Quite a bit oversized, it seems to me. The hvac installers estimated the heat input going into the original furnace (by timing the 1 cu ft dial on the gas meter) to be about 70,000 btu in my 4,000+ sq ft drafty 1920 Englich tudor, 1/2 mile from NYC.
The OP's 300,000 total btu is thus over 4 times mine! Mebbe he *is* in Alaska.
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EA



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> Emphasis on the following. You will be decreasing the input and
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On Sat, 17 Oct 2009 00:49:00 -0400, "Existential Angst"

    Yeh, but that was just the pilot light :-0

    Seeing as you have no clue, STFU.
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On Oct 16, 9:19pm, kris60660_at_yahoo_dot snipped-for-privacy@foo.com (heartmd) wrote:

Your calculations are not exactly right. For one thing you also have a hot water heater and drier which are part of your gas bill and that part will not reduce with a higher efficiency furnace. Next you are adding insulation, so your gas bill will be less regardless so you can not really use that $2280 figure. Third, in case you are counting, you need to take into account the income you could get by investing the money somewhere else other than in new furnaces. And of course subtract income taxes from that investment return. And then the price of gas could go up or even down. But more likely up with Obama trying to solve global warming.
But I will say that furnaces that vary the amount of gas burned depending on the outside temperature are great comfortwise. Nice gentle heat , less drafts due to excessive air being blown thru the ducts. And may make sense financially. I would think the variable furnaces would get even higher efficiencies when burning at the lower rates. However this may already be built into the advertised efficiency.
Dan
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heartmd wrote:

Go for it. Make sure to get a competent installer and get a 10 year P&L warranty to have a peace of mind.
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Stormin Moron has a point!! Altho it's not evident here, it's more evident in the 10/6 post Furnace or Thermostat issue? by JKirkby. Stucco somehow announces itself.
If you go to http://www.thestuccocompany.com/hvac/1.htm , you'll see that alt.hvac is hijacked there, leading one to believe it is Stucco's own forum! wow.... this is an artfully/diabolically "monetized" website, essentially pirating web resources for its own revenue.
So I don't think heartmd was posting *from* there, but most of ouir posts do appear there. Except my Mr. Slim post does not appear there -- yet.
--
EA


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Stormin Moron does have a point, and he has been asked in th epast to wear a hat to keep it covered.
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