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  1. #27
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,767
    If your getting 1000 btu's per cf of ng, and the manufacture states 3.5"wc, and you adjust the valve to 4", then the furnace is over fired.

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  2. #28
    Join Date
    Nov 2004
    Location
    CA
    Posts
    238
    phosgene


    <<<A unit is overfired if its actual burner firing rate, which is obtained by clocking the meter, is greater than its manufacturers rated input. So to say a unit is overfired because it is getting 4"WC as opposed to 3.5" WC I would say is wrong. All you could say is the pressure is to high and you either need to correct it or get a smaller orifice. High pressure may cause overfiring, but a unit is not considered overfired because of it.>>>

    ... this is exactly the line of mine thinking,






    and now Beenthere says

    <<<beenthere
    Professional Member

    Registered: Jan 2004
    Posts: 5933


    If your getting 1000 btu's per cf of ng, and the manufacture states 3.5"wc, and you adjust the valve to 4", then the furnace is over fired.>>>>




    Surely, it is confusing ... or may be the normal GV fluctuation of 0.5"w.c. is insignificant and does not affect the firing rate, thus the GV could be at 4"w.c. and yet the furnace is still within the manifact. firing rate.

    I guess an experiment on my own furnace is overdue.

  3. #29
    Join Date
    Feb 2004
    Posts
    2,458





    Surely, it is confusing ... or may be the normal GV fluctuation of 0.5"w.c. is insignificant and does not affect the firing rate, thus the GV could be at 4"w.c. and yet the furnace is still within the manifact. firing rate.

    I guess an experiment on my own furnace is overdue. [/B][/QUOTE]

    Enlighten me on the "normal flucuation of .5"wc". I don't remember seeing that. I wish I could remember the name of the furnace and the valve name,however it is used in mobile homes and a flucuation like that would mean a huge difference in input. To adjust reg you had to hold your breath it was so touchy

  4. #30
    Join Date
    Nov 2004
    Location
    CA
    Posts
    238
    mike3,

    I do not know why I beleive I've seen (or read) it somewhere that the gas valves work in a range of 0.5" w.c. ... or was it 0.05"w.c.

    Or simply put a range between 3 to 4"w.c. I may be really off on this, but if I can find where I've read it, will post it.


    Oh, wait ...... I just ran to my truck and I am now looking at "White Rogers" GV model 36C84 Series (natural gas), very common GV.

    On page 4, it says - "If a valve has been factory adjusted for the 2.5"w.c. to 5"w.c. range for natural gas, it can not be field adjused outside of that range"



    I also grabbed another GV manual. This is 2 stage "White Rogers" used in 2004-2005 Carrier.
    On page4, it says - Low Pressure will be Factory - adjusted in the 1 to 4" range and High joutlen pressure will also be factory-adjusted in the 2 to 5"w.c.


    If you have more info on this, plese keep me posted.

  5. #31
    Join Date
    Feb 2004
    Posts
    2,458
    Originally posted by bananaboy
    mike3,

    I do not know why I beleive I've seen (or read) it somewhere that the gas valves work in a range of 0.5" w.c. ... or was it 0.05"w.c.

    Or simply put a range between 3 to 4"w.c. I may be really off on this, but if I can find where I've read it, will post it.


    Oh, wait ...... I just ran to my truck and I am now looking at "White Rogers" GV model 36C84 Series (natural gas), very common GV.

    On page 4, it says - "If a valve has been factory adjusted for the 2.5"w.c. to 5"w.c. range for natural gas, it can not be field adjused outside of that range"





    I also grabbed another GV manual. This is 2 stage "White Rogers" used in 2004-2005 Carrier.
    On page4, it says - Low Pressure will be Factory - adjusted in the 1 to 4" range and High joutlen pressure will also be factory-adjusted in the 2 to 5"w.c.


    If you have more info on this, plese keep me posted.

    Thanx for the reply. However the above listed are factory ranges not "drift".


  6. #32
    Join Date
    Nov 2004
    Location
    CA
    Posts
    238
    mike3

    I agree with you, however I am still digging


    Tell me, in your opinion, do the GVs have any marginal range which they work within - or manifacturers strictly demand 3.5"wc. Period.

    I still think that there is a marginal WORKNIG range for the GV.

  7. #33
    Join Date
    Feb 2004
    Posts
    2,458
    [QUOTE]Originally posted by bananaboy

    I still think that there is a marginal WORKNIG range for the GV. [/B][/QUOTE

    You could be right. I just don't remember seeing that. Unless and I know I might be stretching, the vibration could cause reg adjust to move. I know when we set new regs at meter we leave them 1/2" higher and then they settle in at 7"

  8. #34
    Join Date
    Feb 2005
    Location
    small island in the Pacific Ocean
    Posts
    558
    I will ask my B Gas Fitter Course instructor his opinion tomorrow night. I believe in my earlier statement but am now curious about how much fluctuation a valve can handle without needing to be adjusted.

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