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Thread: Gas Pressure

  1. #1
    Join Date
    Jan 2001
    Posts
    41

    Two weeks ago a technician came to our house (in Broken Arrow, Oklahoma) for our semi-annual "Energy Savings Agreement" service call. I have been very satisfied using this same company for over 20 years. This call was to service the furnaces. Our gas furnaces are Goodman, GMP100-4-RevB and GMP050-3-RevB. Included in the work performed was the following for both units:

    1) Cleaned burners and exchanger
    2) Cleaned flame sensor
    3) Adjusted gas pressure to 3.5

    I hadn't thought anything of the work performed until yesterday when I read some disturbing information on this forum regarding adjusting gas pressure. Is a gas pressure adjustment to 3.5 safe or should I be concerned?

  2. #2
    Join Date
    Oct 2004
    Posts
    3,400
    3.5" W.C. is the most common setting for a regulator on an appliance using natural gas.

    That being said, there are quite a few appliances that use pressure settings other than that setting (usually higher).

    If you want to verify the proper setting for your furnace, find the model & serial number "plate". It is usually inside the door where the burners are found.

    Look for the "manifold pressure" number.

    If it is anything other than 3.5, call them & ask for an explanation.

    Most likely, it was done right.


  3. #3
    Join Date
    Apr 2004
    Posts
    7,680
    I agree, 3.5" is industry standard for most gas fired furnaces. Feel confident that the compnay who has serviced you has continued to do what is right.

  4. #4
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,052

    Hmm dittos

    Yes, read the rating plate as 3.5 inches of water column (abbreviated w.c. or wci) is the most common. This tech gets a cookie. So it also begs the question: what the heck has everyone else been doing for the last 20 yrs? Apparently, this unit has been overfiring since it was installed. The unit could be damaged. Did he test for heat exchanger cracks, CO leakage, and do a combustion analysis? Don't celebrate too soon. This unit should have been set properly at installation. Now, you have a big question about its longevity.

    FYI, this is just the manifold or burner pressure. You also have to be concerned with the inlet pressure under load.


  5. #5
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,052

    Hmm dittos

    Yes, read the rating plate as 3.5 inches of water column (abbreviated w.c. or wci) is the most common. This tech gets a cookie. So it also begs the question: what the heck has everyone else been doing for the last 20 yrs? Apparently, this unit could have been overfiring or underfiring since it was installed. The unit could be damaged. Did he test for heat exchanger cracks, CO leakage, and do a combustion analysis? Don't celebrate too soon. This unit should have been set properly at installation. Now, you have a big question about its longevity.

    FYI, this is just the manifold or burner pressure. You also have to be concerned with the inlet pressure under load.


  6. #6
    Join Date
    Jan 2005
    Location
    Gilroy, Calif
    Posts
    188
    Did he adjust it up or down? Why was it out of adjustment it the first place? Yeah, great job in checking the pressure but if there is an obstruction in the orfices than when it becomes dislodge, could have more problems. Should have check orfices before adjusting inlet pressure. Just my opinion.

  7. #7
    Join Date
    Jan 2001
    Posts
    41

    I'm sorry if I mislead anyone. I've been using the same HVAC company for 20 years. However, that service history covers three different houses. My current furnaces are only four years old and were installed during construction of my current house (June 2001), and were not installed by my longstanding service company.

    I'm not sure whether the technician adjusted the gas pressure up or down, or by how much. He made a comment about the high cost of gas, so I assumed he adjusted the pressure slightly downward. Since the units performed well over the previous four winters, I'm sure it was only a minor adjustment. I inspected the rating plate on each unit last night and they both show a manifold pressure rating of 3.5.

    I want to thank everyone who responded for his or her information, advice and concern. I feel confident that my furnaces are operating properly and have not sustained any potentially long term damage.

    Thanks again.

  8. #8
    Join Date
    Oct 2004
    Posts
    3,400
    Originally posted by RED

    ... He made a comment about the high cost of gas, so I assumed he adjusted the pressure slightly downward. ...
    Thanks again.

    Please don't assume.

    Lowering the pressure regulator setting will NOT necessarily save gas.

    It is not that simple.



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