Should I replace a 9 year old furnace?

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I am getting a new central A/C unit that has seen better days. It's 15+ years old, and it finally died. I was told they have to replace something above the furnace (the condesor?). While they are here working on my furnace, should I just get a new furnace too??
I have a Lennox furnace that is still working, but it's 9+ years old. Manufactured in early1993.
Of course, they are offering me a package deal to also replace the furnace if I want. Initially I said no, but I have no idea the average life expectancy of an average furnace. If they only last 12 years (on average), I hate to have them back out in a year or so.
Looking for advice for anyone that was in my situation.......
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If it 80% or less efficent and you have a long heating season, run the numbers. to see what you will save with a 94%. Otherwise no I wouldnt
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I am no expert but in my experience, a furnace will last much more than 10 or 12 years, and that is in a cold climate where it gets lots of use. At the very least, I would get another heating contractor to come by and see what he recommends, why and at what price. Even if he charges you a service call for doing so. A second opinion is worth it for the peace of mind that you are not being cheated by the first contractor. If the first contractor objects strenuously to you getting a second opinion, I think that tells you something. You might want to post your message in alt.hvac
Good luck!
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our furnace is probably 50 years old. it's a big cast iron thing.
everyone we asked told us not to change it because new furnaces have crappier construction.
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You don't say if your furnance is liquid or gas fueled.
If the former, a furance of this vintage would be classified as a 'Pot-burner' and is considered to be very low efficiency.
In '69 I purchased a old house with a cast iron oil furnace. Used it for one winter and found it to complicated to light for my wife, when I was away from home for the beginning of the heating season.. She has to have the serviceman come and that cost about $20..
The second season I installed a modern fuel oil furnace with all automatic controls. Not only was it easier to operate (never had to light it), but it was WAY MORE cost efficient. Since I did the installation myself, I only had the cost of the furnace. I think I had the new furnace paid for in fuel savings with in 3 years (when I sold the house).
--
My opinion and experience. FWIW

Steve



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one
I assume you're talking to me.
it's oil-burning. we've had this house for 2 winters already, this is the third. it burns a lot of fuel, but the house has poor insulation (50 years ago they had no insulation in the walls) and our consumption is similar to other people's.
I don't understand what you mean by "hard to light" it lights itself. we have a thermostat that controls the burner. we don't light anything.
what do you consider as part of the furnace? the tank is cast iron and 50 years old, but the burner is not that old.
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jj Your unit is probably 50 % efficent . You could put in a 90+ . And your blower is taking alot more KWH than the new ones.. You should replace it.
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Then you are asking the wrong people. Granted, they dont make tanks anymore.

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CBHvac wrote:

Hi, Big cast iron thingy alright but at what efficiency? Maybe your dollar is going up the chimney more than heating your house. How about doing some cost anaysis? Tony

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50% or 60% maybe? Seen a few old oil units that MIGHT make it to the 50% range...and have seen more than one Chrysler Airtemp gas unit that was feeling frisky if it saw 65%....

Bingo...
With AFUE ratings, its simple.. Figure, just on fuel, that if you have a 60% unit, 60 cents of the heat generated, goes into the home, with 40 cents going off to heat the world... now, with a 95% unit, only 5 cents goes away...not including the savings on more energy friendly motors and controls.

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so, let's say current furnace is 50% efficient. let's say we get a 90% efficient one. how much less fuel is that per year?
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j j wrote:

If H is the amount of heat needed in a given situation, for example, to heat your house this Winter:
Let x = the amount of fuel it takes to produce H by a 50% efficient furnace y = the amount of fuel it takes to produce H by a 90% efficient furnace
Therefore:
.50x = .90y
So, y = (5/9)x = .56x
In other words, a 90% efficient furnace uses only 56% of the fuel used by a 50% efficient furnace to produce the same amount of heat. So, a 90% efficient furnace (THEORETICALLY) should save 44% in fuel. However, I suppose YMMV.
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Ermalina wrote:

BTW, we live in the Midwest (COLD winters) and have a 25 year-old Amana Air Command that is going strong and will not be replaced until it dies or develops serious probs. The folks (a family business which has been around for 3 generations) who maintain it, and who will be doing the installation of the new one which replaces it, agree.
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About 40%.
--
Christopher A. Young
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Give or take your situation, and usage, between 55%% to 62% less..Installed correctly, depending on your fuel costs not, it could, theoretically, have a tremendous payback. Altho, I dont sell on the payback theory, since you have to pay to get it installed, and it does cost every time you turn it on.

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what determines the efficiency of a furnace?
is it the fact that it's a tank (are modern furnaces different?) or the burner itself?
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90% vs 50 = 40% savings, . One gas one is 96.6% , many are 94 and 95%. And a variable speed blower may save 75% on your old units blower KWH cost. Not knowing how much it runs It cant be figured , but it could easily save 15$ a month in electric costs and boost SEER for central air by 1 seer. Plus not pullng inside air for combustion helps. Your unit wasnt designed for efficency. Nothing was then.
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The design, and the final AFUE rating.

Both. Todays furnace isnt the one that you had when you grew up...(well..for some it might still be..LOL) but seriously, huge design changes, computer controls, secondary heat exchangers, better blowers...it all adds up.

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In my opinion the only thing your going to gain from a new furnace it a bit more sophisticated combustion controls and a new warrantee.. You may also benefit from the fact that if something doesn't work properly on the totally new installation, your installer and the OEM are totally responsible, without dispute.
Selling you a new furnace just increases the AC installers profit margin and simplifies his installation a bit..
But to answer your question, I would say 20 years is the outside limit on a furnace.. There are a few elements in the combustion chamber that can burn out but these can be replaced. Combustion controls have go to electronic, but the old electrical stuff has worked fine for a long period and could be depended on into the future or that could be up dated in an older unit.
The only time I would recommend upgrading is when someone has a furnace that dates back to the 50s where fuel was very cheap and efficiency was not a factor in the design. Anything from the late '70s on will be built with a much higher efficiency and reliability.
--
My opinion and experience. FWIW

Steve



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