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Vintage Nat Gas Furnace advice needed

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My Daughter just purchased a home built in 1950. It looks to have the original furnace (or close to it) still in place. There is no badging left on it so my first question is does anyone know what make or model it is? I found the picture attached online, her unit is identical to it but I can't make out the label in the pic
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Second, the furnace appears to be functioning just fine. So what is the argument for replacing with a modern high efficiency unit? Obviously fuel savings (we live in Alberta, so Nat gas is relatively cheap, but that isn't to say it is cheap. We currently pay about $5.50/GJ ($5.85/MMBtu) But what would be the thermal efficiency of this unit versus a new high efficiency unit? The house is 1250 square feet, so while it does get pretty cold here it isn't that much volume to heat.

What are your thoughts?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,536
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    The efficiency of a new furnace will, of course, be better. In fact, I wouldn't be at all surprised if a furnace would use only about two thirds of the gas the old one did.

    But...

    At your price for gas, is it going to pay to replace the old one if it's working just fine? Most likely not, but do the math.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • pecmsg
    pecmsg Member Posts: 4,909
    edited November 2022
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    Congrats on your daughter's new home.

    That gas price is not bad but I can almost guarantee its going up!

    1st get a Defender Low Level CO Detector!!!

    Have that unit serviced buy a qualified contractor, if its sound use it this winter. Look into tightening the envelope, window, doors, insulation anything that will keep the heat in. Now you can lower the size of the furnace and save on gas. Begin searching Dual Fuel systems. Heat pump and gas fired furnace.
    GGross
  • mattmia2
    mattmia2 Member Posts: 9,838
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    You will have to find someone that understands these older systems to service it, someone that knows how to clean and adjust the burner, how the older gas controls work, and how to do a combustion analysis. Maybe there are now techs out there that would be confused by the fan/limit control not being part of a pc board.
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,898
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    Second, the furnace appears to be functioning just fine. So what is the argument for replacing with a modern high efficiency unit? Obviously fuel savings (we live in Alberta, so Nat gas is relatively cheap, but that isn't to say it is cheap. We currently pay about $5.50/GJ ($5.85/MMBtu) But what would be the thermal efficiency of this unit versus a new high efficiency unit? The house is 1250 square feet, so while it does get pretty cold here it isn't that much volume to heat.


    Is anyone making the argument? Keep it until it breaks then install a properly sized replacement.
  • pecmsg
    pecmsg Member Posts: 4,909
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    Second, the furnace appears to be functioning just fine. So what is the argument for replacing with a modern high efficiency unit? Obviously fuel savings (we live in Alberta, so Nat gas is relatively cheap, but that isn't to say it is cheap. We currently pay about $5.50/GJ ($5.85/MMBtu) But what would be the thermal efficiency of this unit versus a new high efficiency unit? The house is 1250 square feet, so while it does get pretty cold here it isn't that much volume to heat.
    Is anyone making the argument? Keep it until it breaks then install a properly sized replacement.
    I’m saying get it checked then wait until next year
    Hot_water_fan
  • bburd
    bburd Member Posts: 926
    edited November 2022
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    Some of those older furnaces were built like tanks and will last a long time. The most important points are the integrity of the heat exchanger, safe operation and correct combustion adjustment, which should be set with a combustion analyzer by someone who knows how to use it.

    The difference in efficiency is probably about as @Jamie Hall said above. Reliability may be  better than a new furnace because the controls are less complicated on the older ones.



    Bburd