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Old 07-20-2010, 03:23 PM   #1
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When to replace a furnace?

I know it's summer time, however I have a question that was raised during the winter by my Gas Company.

I have a floor furnace in my house that is probably 80 years old. Here where I live, I can phone the gas man to come out for a free inspection.

About 5 years ago, the gas man came out and and commented about how he loves the Coleman floor furnace and wished he had one in his house. He stated everything is running fine. He also stated that if I ever had to replace the furnace, I will never find one that works so well.

6 months ago I had another free safety inspection. This gas man was the total opposite. He stated the life of a furnace is 20 years and I should replace it now. Although he didn't say there was anything wrong with it that he can see, he just didn't like the age of the furnace. BTW - to properly inspect the furnace, the gas man was suppose to crawl underneath the house in the crawl space to inspect the underside of the furnace. He did not crawl underneath the house. I'm thinking that maybe he just told me to replace the furnace because it was easier for him to say that then to do a complete inspection.

What do you think I think?


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Old 07-20-2010, 04:19 PM   #2
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if there is nothing wrong with the furnace, don't replace it. ask the guy if he doesn't like the age of his wife if he will replace her, even if she works just fine.


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stanlam (07-22-2010)
Old 07-20-2010, 04:39 PM   #3
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For the HVAC survey I did but no longer have 80 YO was the longest lived piece of HVAC equipment out of about 100 samples so if my samples were truly representative of the whole population of the millions of furnaces out there, your unit has outlived 99% of them.

If these things tend not to fail catastrophically then wait. Have 3 CO detectors in your house.

If you can estimate the efficiency of this old furnace then it becomes sort of an 'annuity calculation' as to replacement. Pay too much for fuel each month or pay a lump sum now for a new furnace that is more efficient.
Search phrases are "present value of an annuity" and "future value of an annuity" for the formulas.

I get 24 years +/- 3 years for the replacement age of HVAC equipment. Equipment failure is longer than this.

Last edited by Yoyizit; 07-20-2010 at 05:48 PM.
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stanlam (07-22-2010)
Old 07-20-2010, 07:21 PM   #4
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Those old floor furnaces last and last and last. As long as no forgets and covers them up with a throw rug while they're using them. Or the crawlspace floods.

If it has no holes in it, and the safeties work. And it doesn't get cover while its on, or flooded with water. You might get another 20 plus years from it.
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