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Dating a Sears furnace


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Originally posted by Erby

Gotta be careful with the freezers PHillip. They'll give you a bad case of blue b*&^s.

I don't have any personal experience but I hear they don't put out so well.

Erby,

I know freezers are that way, That why I have a whirlpool tub on the side.[:-dev3][:-ashamed

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  • 3 years later...
  • 2 weeks later...

can anyone confirm the age?

another thread where there was a decoder indicated there are three different ways to decode a sears furnace:

Sears 3 types

1) A letter followed by two #’s in S# are year ex: R883512345 = 1988

2) (1980-1989) The first digit (a letter) is decade followed by a number ex: H6113930 = 1986

3) If S# is all #’s, 3rd and 4th are year ex: 22880018 = 1988

makes more sense using the second method. i get 1985. this looks much closer to what i thought it was by looking at the furnace. (sorry for reviving this old thread)

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can anyone confirm the age?

another thread where there was a decoder indicated there are three different ways to decode a sears furnace:

Sears 3 types

1) A letter followed by two #’s in S# are year ex: R883512345 = 1988

2) (1980-1989) The first digit (a letter) is decade followed by a number ex: H6113930 = 1986

3) If S# is all #’s, 3rd and 4th are year ex: 22880018 = 1988

makes more sense using the second method. i get 1985. this looks much closer to what i thought it was by looking at the furnace. (sorry for reviving this old thread)

Post a picture of the furnace.

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I agree with Chad, it does look older than the eighties. Based on the corrosion, I'd say that humidifier has trashed that puppy. Better prepare the family for Grandpa's sudden demise, he isn't simply in the nursing home; he's on life support with 24-hour-a-day monitoring and a crash cart parked next to his bed and is liable to pass at any moment.

Make sure you tell them that or don't be surprised when some cold night you get a call from the client bemoaning the fact that an HVAC guy just left the house and told them they need a new furnace now and couldn't figure out how their inspector hadn't told them that.

ONE TEAM - ONE FIGHT!!!

Mike

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lol, it's my furnace. the rust on the bottom is from when the A-coil drip pan was clogged and leaked inside the bottom of the furnace. lived in this house for 3 years, only problem i've ever had was the blower motor went out a couple of weeks ago. i know it needs replaced, hoping to get another 2-3 years though.

where do you come up with 1968 from the serial #?

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lol, it's my furnace. the rust on the bottom is from when the A-coil drip pan was clogged and leaked inside the bottom of the furnace. lived in this house for 3 years, only problem i've ever had was the blower motor went out a couple of weeks ago. i know it needs replaced, hoping to get another 2-3 years though.

where do you come up with 1968 from the serial #?

It's from the '60s, probably 1965. It might not be possible to verify that for certain at this point.

It was a very basic machine with little to go wrong with it. The only reason to eventually discard it would be if the heat exchanger developed a crack or hole. Someone could determine that with a tracer gas test.

In the meantime, get yourself a couple of good carbon monoxide alarms.

Otherwise enjoy heating your house with a neat old furnace.

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thanks for the advice. 1965 would make sense, the guy who owned the home before me bought it in 1964 and did a lot of renovations right away. i've got a CO alarm at the top of the basement stairs, is that sufficient? or should i put another closer to the furnace?

the reason i want to replace it is for efficiency. it's an 80% with 150k btu input 120k output. a program i used (HVAC-Calc Residential) to calculate what size i needed shows ~ 80-90k btu. so with a 95% @ 90k btu output i'd be cutting out ~ 55k btu on the input side. that should save me 36% on gas. if i insulate my attic, basement, and ductwork the program says i could go with 70k btu. that would save ~ 50%.

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thanks for the advice. 1965 would make sense, the guy who owned the home before me bought it in 1964 and did a lot of renovations right away. i've got a CO alarm at the top of the basement stairs, is that sufficient? or should i put another closer to the furnace?

the reason i want to replace it is for efficiency. it's an 80% with 150k btu input 120k output. a program i used (HVAC-Calc Residential) to calculate what size i needed shows ~ 80-90k btu. so with a 95% @ 90k btu output i'd be cutting out ~ 55k btu on the input side. that should save me 36% on gas. if i insulate my attic, basement, and ductwork the program says i could go with 70k btu. that would save ~ 50%.

Your logic is faulty and your numbers are way, way off. First of all, if you're considering a new furnace, leave the insulation out of the equation. The benefit of the insulation is independent of the furnace decision.

Next, you won't see anywhere near a 36% savings on gas from just changing the furnace. BTUs is BTUs. You need to figure your heating needs in terms of how much heat the house loses, not how much heat the furnace produces. You have to make up that loss. That loss is your heating requirement - a smaller furnace will be more efficient at meeting the requirement, but not *that* much more efficient.

When you go from an 80% to a 95% all you get is 15 percentage points better than you had before. That represents about an 18% improvement. So to figure your payback period, figure your cost to operate just the furnace for one year and then figure that amount less 18%. Divide the cost of the new furnace by the difference between those two numbers to figure out how many years it'll take to pay for the new unit. My guess is that it'll be a long time.

Also, the efficiency of the heating system is not dicated by the furnace as much as it's dictated by the duct system. If your system is typical, even with an 80% furnace, you're lucky if you're actually seeing 50% efficiency. Oddly enough, replacing the furnace alone won't boost that number by 15 points. You might only see 60% when you're done. If you want the system to be efficient, you'll need a quality duct system -- and that could cost almost as much as the furnace.

Energy efficiency is great an all that, but doing it right usually costs too much money to make it worthwhile.

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didn't really mean to say it would save 36% on how much gas i would use. but the 36% smaller furnace would cycle less, matching the needs of my house better. i would think that would help as well as the 80% vs 95% thing.

don't you have to figure your home's heat loss by the size and type of insulation you have? as well as many other factors. have you ever used hvac-calc? is it accurate? http://www.hvaccomputer.com/

my ductwork seems tight with very few air leaks, but it looks kind of like an octopus. the program shows if i insulate my ductwork i would lose 5k btu less heat. i don't plan on re-doing my ducts, but possibly insulating them.

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didn't really mean to say it would save 36% on how much gas i would use. but the 36% smaller furnace would cycle less, matching the needs of my house better. i would think that would help as well as the 80% vs 95% thing.

Yes, it definitely helps. It's like the difference between driving your car in stop & go traffic and driving it on the highway. It'll also make the house more comfortable.

don't you have to figure your home's heat loss by the size and type of insulation you have? as well as many other factors.

Yes, certainly. But earlier, it seemed to me that you were implying that improving the insulation would improve value more with a new furnace than with an old one. This, of course, isn't the case. If you improve your insulation, you reduce the building's heat loss.

have you ever used hvac-calc? is it accurate? http://www.hvaccomputer.com/

I've never used it, but I'm familiar with it and I know a pro who uses it. It seems to be a kick ass program. I wish all pros would use it. Most heating systems that I see are absurdly over sized.

my ductwork seems tight with very few air leaks, but it looks kind of like an octopus. the program shows if i insulate my ductwork i would lose 5k btu less heat. i don't plan on re-doing my ducts, but possibly insulating them.

I doubt that they're really tight even if they look like they are. Unless there's mastic on the joints, they probably leak like a sieve. If the ducts pass through unconditioned spaces, and if your tight-looking duct work is typical, losses through the unsealed joints are probably at about 30%. That's huge. If you *seal* your ducts *and* insulate them, you'll probably see greater savings than you would if you simply switched from an 80% to a 95% furnace.

It's almost never cost-effective to junk a working 80% furnace in favor of a more efficient one. The savings in operation just aren't great enough to justify the cost.

This is true of a lot of supposed energy upgrades. I see people spending thousands on new windows and new attic insulation. These people will *never* see savings from these projects.

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It's almost never cost-effective to junk a working 80% furnace in favor of a more efficient one. The savings in operation just aren't great enough to justify the cost.

James, in case you haven't noticed we are in a recession. If this guy wants to replace his furnace he will provide work for a tech, help to keep his local HVAC company solvent, and he'll contribute to the preservation of manufacturing jobs. He'll also save energy, which is good for the economy and the environment. He won't be saving any of his own money, but he will be contributing to the greater good. Advising consumers to not spend money is unpatriotic. [;)]

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It's almost never cost-effective to junk a working 80% furnace in favor of a more efficient one. The savings in operation just aren't great enough to justify the cost.

James, in case you haven't noticed we are in a recession. If this guy wants to replace his furnace he will provide work for a tech, help to keep his local HVAC company solvent, and he'll contribute to the preservation of manufacturing jobs. He'll also save energy, which is good for the economy and the environment. He won't be saving any of his own money, but he will be contributing to the greater good. Advising consumers to not spend money is unpatriotic. [;)]

All true.

Jakeb, you should buy two new furnaces.

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It's almost never cost-effective to junk a working 80% furnace in favor of a more efficient one. The savings in operation just aren't great enough to justify the cost.

James, in case you haven't noticed we are in a recession. If this guy wants to replace his furnace he will provide work for a tech, help to keep his local HVAC company solvent, and he'll contribute to the preservation of manufacturing jobs. He'll also save energy, which is good for the economy and the environment. He won't be saving any of his own money, but he will be contributing to the greater good. Advising consumers to not spend money is unpatriotic. [;)]

All true.

Jakeb, you should buy two new furnaces.

Yeah, but they say good things come in threes.

ONE TEAM - ONE FIGHT!!!

Mike

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