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    Bonnet capacity (5 Posts)

  • charliechicago charliechicago @ 10:35 AM
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    Bonnet capacity

    Hello to all
    What does bonnet capacity mean.
    I have a friend that wants to replace his forced hot air system that says input 100000 btu bonnet capacity 80000 btu
    I know it differs from afue but is this an 80% furnace?
    Thanks Michael
  • Robert O'Brien Robert O'Brien @ 12:38 PM
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    Bonnet is output
  • charliechicago charliechicago @ 1:10 PM
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    Chimney liner

    So if I replace it with an 80% I don't need a liner?
  • Ironman Ironman @ 2:31 PM
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    Not 80%

    That's not an 80% furnace, it's probably 65% at best. Any thing that would have "bonnet capacity" stamped on it is probably at leas 35 years old, maybe much more.

    A new 80% furnace must have a liner installed with it to prevent flue gas condensation. By the time you pay for that, you could have gotten a 95% one and been better off in most cases.

    Also, a heat loss calculation needs to be done as the old furnace is probably way over-sized for the house and a higher efficiency furnace would have more output.
    Bob Boan

    You can choose to do what you want, but you cannot choose the consequences.
  • charliechicago charliechicago @ 10:13 PM
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    Iron man

    Thank u for the response. You are right that it's an old furnace as you can see from the picture. I had been told exactly what u said but I wanted confirmation. Also that's a great idea about a condensing unit. But I'm still wondering what exactly does bonnet capacity actually mean. Thanks mike
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