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  1. #40
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    Nov 2001
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    east kansas
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    I'm doing this from memory. The pressure switch looks at the differential pressure of the orifice that is built into the cold end header box. The reasoning is if the heat exchanger is restricted the differential switch would not make, but a regular vacuum switch would. This is engineered to protect against heat exchanger problems,and the occupants of the building.

    Using the wrong, and I do mean wrong, vacuum switch put the building and occupants in danger. Just this fall at our Lennox Dealer Training the FTC stated this type of practice is not to be done. You are taking all responsibility for anything that goes wrong.

    Space heaters or motel is a better option than installing a wrong, and this case, a blatantly wrong part even just for temporary.
    Beware of advice given by some guy on the Internet.

  2. #41
    Join Date
    Feb 2010
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    In a boiler room
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    6,915
    .

  3. #42
    Join Date
    Nov 2001
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    east kansas
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    Quote Originally Posted by ch4man View Post


    how come i got beat up and he didnt?

    .
    Because I'm better looking.
    Beware of advice given by some guy on the Internet.

  4. #43
    Join Date
    Jan 2007
    Location
    Mn the state where absolutey nothing is allowed
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    1,312
    Quote Originally Posted by Milk man View Post
    I'm doing this from memory. The pressure switch looks at the differential pressure of the orifice that is built into the cold end header box. The reasoning is if the heat exchanger is restricted the differential switch would not make, but a regular vacuum switch would. This is engineered to protect against heat exchanger problems,and the occupants of the building.

    Using the wrong, and I do mean wrong, vacuum switch put the building and occupants in danger. Just this fall at our Lennox Dealer Training the FTC stated this type of practice is not to be done. You are taking all responsibility for anything that goes wrong.

    Space heaters or motel is a better option than installing a wrong, and this case, a blatantly wrong part even just for temporary.
    your close........

    a differential switch will not make if the intake or exhaust is plugged, but will make up sooner with a plugged heat-x. differential is pressure drop. a plugged heat-x is a greater pressure drop, as in greater differntial

    Quote Originally Posted by Milk man View Post
    Because I'm better looking.
    your not even close
    my boss thinks its possible to repeal the laws of physics

  5. #44
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    Jan 2007
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    Mn the state where absolutey nothing is allowed
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    oops my explaination was aimed at furnaces that measure the differential across the heat-x's. the lennox pressure switch wont make with a restricted secondary. a carrier will
    my boss thinks its possible to repeal the laws of physics

  6. #45
    Join Date
    Nov 2001
    Location
    east kansas
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    Quote Originally Posted by ch4man View Post
    your close........

    a differential switch will not make if the intake or exhaust is plugged, but will make up sooner with a plugged heat-x. differential is pressure drop. a plugged heat-x is a greater pressure drop, as in greater differential




    your not even close
    I disagree when it comes to Lennox. The differential is measured at the orifice in the CEHB. If you have a plugged HX there will not be a pressure difference measured at the orifice. The draft motor will cause a vacuum of near equal amount at the orifice.

    The HX restriction will act as a wall to anything upstream on the combustion air side. I will see the same vacuum on the heat exchanger side of the orifice as the draft motor side. This is why Lennox engineered the the CEHB this way.
    Beware of advice given by some guy on the Internet.

  7. #46
    Join Date
    Nov 2001
    Location
    east kansas
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    I type slow.
    Beware of advice given by some guy on the Internet.

  8. #47
    Join Date
    Jan 2007
    Location
    Mn the state where absolutey nothing is allowed
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    1,312
    hey i read slow, didnt see my mistake untill after the edit time elaplsed
    my boss thinks its possible to repeal the laws of physics

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