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  1. #14
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    Jul 2006
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    Southern Ca, Elkton Md
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    Quote Originally Posted by RoBoTeq View Post
    I understand what you are saying, but for a badly operatiing condensing furnace to operate at a lower efficiency then the best running 80% furnace, that condensing furnace would be shutting down on one safety or another.

    Besides, when we get into these scenarios we must assume that the equipment is operating as it was intended to do so.
    I see it more often then you would think!

    I have calculated 90% running at 67%, with no problems other then gas consumption. Thats what a combustion analyzer is for. And the customer loves you next month when they get thier bill!

    But yeah, for this scenarios we are assuming that everything is operating properly.
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  2. #15
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    Jul 2004
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    midwest
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    Quote Originally Posted by weber View Post
    I see it more often then you would think!

    I have calculated 90% running at 67%, with no problems other then gas consumption. Thats what a combustion analyzer is for. And the customer loves you next month when they get thier bill!

    But yeah, for this scenarios we are assuming that everything is operating properly.
    What did that furnace have for an exhaust temperature?

  3. #16
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    Just wondering why no reply?

  4. #17
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    Quote Originally Posted by trane View Post
    Just wondering why no reply?
    Wow, I didn't know there was a specific time I had to answer your questions in. You do know its a monday morning, right? Lots to do!
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  5. #18
    Join Date
    Jul 2006
    Location
    Southern Ca, Elkton Md
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    Quote Originally Posted by trane View Post
    What did that furnace have for an exhaust temperature?
    I dont have an exact # to give you, because everytime I see this problem it could be high or it could be low. It depends on what is causing the issue and what repair needs to be done to correct it.
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  6. #19
    Join Date
    Feb 2008
    Location
    Everett, Wa.
    Posts
    88
    Quote Originally Posted by weber View Post
    I see it more often then you would think!

    I have calculated 90% running at 67%, with no problems other then gas consumption. Thats what a combustion analyzer is for. And the customer loves you next month when they get thier bill!

    But yeah, for this scenarios we are assuming that everything is operating properly.

    Wouldn't that have a melted flue?

  7. #20
    Join Date
    Jul 2006
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    Southern Ca, Elkton Md
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    Quote Originally Posted by buttwheat View Post
    Wouldn't that have a melted flue?
    Why would a lower or slightly higher then normal temp melt a pvc flue?
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  8. #21
    Join Date
    Feb 2008
    Location
    Everett, Wa.
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    88
    Quote Originally Posted by weber View Post
    Why would a lower or slightly higher then normal temp melt a pvc flue?
    If a 90% is running at 67% the exhaust temps. are going to be a little more then slightly elevated. it would turn the pvc in to a limp noodle.

  9. #22
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    Southern Ca, Elkton Md
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    Quote Originally Posted by buttwheat View Post
    If a 90% is running at 67% the exhaust temps. are going to be a little more then slightly elevated. it would turn the pvc in to a limp noodle.
    Thats not true, and I can not give you any technical information to clearify, due to your membership and location of this thread.

    There are many things that go into effecting eff, not always over heating the flue.
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  10. #23
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    midwest
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    Quote Originally Posted by weber View Post
    Thats not true, and I can not give you any technical information to clearify, due to your membership and location of this thread.

    There are many things that go into effecting eff, not always over heating the flue.
    90% less 67% = 23% If its not going out the flue where is it going?

  11. #24
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    Quote Originally Posted by trane View Post
    90% less 67% = 23% If its not going out the flue where is it going?
    Its not always a burning issue but sometimes a mechanical issue were the 23% is not there. Basicly it has been derated. So your 100k furnace is only running a 70k. Your eff as far as what you are burning can still be higher, maybe even 90%, but your input has dropped so your output has dropped, So your are burning ok what you are burnning but you are not getting the proper output due to lack of input.

    So no, the 23% is not going out the flue, because it not there. And thats why you could have a lower flue temp.
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

  12. #25
    Join Date
    Jul 2004
    Location
    midwest
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    Quote Originally Posted by weber View Post
    Its not always a burning issue but sometimes a mechanical issue were the 23% is not there. Basicly it has been derated. So your 100k furnace is only running a 70k. Your eff as far as what you are burning can still be higher, maybe even 90%, but your input has dropped so your output has dropped, So your are burning ok what you are burnning but you are not getting the proper output due to lack of input.

    So no, the 23% is not going out the flue, because it not there. And thats why you could have a lower flue temp.

    Then that 67% number was a mistake?

  13. #26
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    Jul 2006
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    Southern Ca, Elkton Md
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    Quote Originally Posted by trane View Post
    Then that 67% number was a mistake?
    Customer wants 100K furnace, what is being supplied to conditioned space.

    If the customer is not getting 90K btu what are the getting? As far as fuel consumption, thats a different story, and it is on a case by case. Sometimes there will be a 70% out put from a 100k input on a 90%, with a higher flue temp. Im just stating different cases that could cause a lower flue temp.

    I dont keep a record of every sevice call I have every done, sitting next to me. So I cannot supply you with exact #'s.
    "Correct Installation is the Key"

    .1 has killed more HX then Rush Limbaugh

    What is your TESP?

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