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  1. #1
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,400
    what should propane flame look like in a propane fired furnace? should it be almost all blue, like natural gas? I have a goodman that i converted to propane for use in a garage at my vacation home. the flame is about 60-75% blue and the rest is yellow.

    i have asked my boss, coworker, and the supply house, but nobody around here knows anything about propane.

  2. #2
    Join Date
    Feb 2004
    Posts
    2,458
    Blue is nice- However propane tends to yellow tip in my limited experience with it. Are you sure you have adjusted to rated input when you converted?

  3. #3
    Join Date
    Aug 2002
    Location
    manitowoc wisconsin
    Posts
    4,943
    Trying to adjust a flame by color alone is a dangerous practice.At the very least set up with a c.o. meter.Buy a combustion analizer!
    Take your time & do it right!

  4. #4
    Join Date
    Nov 2004
    Location
    Jonesboro, Arkansas
    Posts
    122
    mike3 is right on this. With pressure and secondary air correct the flames will usually have some yellow tipping. In this part of the country there are a lot of LP furnaces.

  5. #5
    Join Date
    May 2004
    Posts
    1,308
    So far Craig, none of these people have steered you wrong.

    If your furnace is a natural draft furnace and the gas valve has been properly derated to the altitude you are. Follow the local codes. IE: 11" W.C. @ Sea level. Less if your location is a higher altitude. (Just call the local airport and ask the 'Tower' what the area's altitude is.

    And as Mark mentioned. You really should do a combustion analysis. If you aren't prepared to do this yourself. Find someone who can. (That's the safe route).

    As for flame characteristics, as menioned a nice cone of blue with very slight yellow tipping. If your Secondary air is correct and your L.P. Gas pressure is set in conformance to local codes and Altitude derate, Then Bob's your Uncle.

    Also, Craig... go over that furnace with a fine toothed comb. Visually inspect the entire heat exchanger if possible. And test all of the safety controls. Of course, if you aren't familiar with all of this... then consult the aid of a Pro. Don't attempt anything if you only know how to light the pilot.


    If you are a tech, and know most of this, I cannot appologize for stating the obvious. A pro accepts anyone offering safe advice.

    If your furnace is a power vented furnace. And all of the pressure and derates are met; you should expect to see a decidedly blue flame the entire length of it on the 'inshot burners'. Most L.P. gas valves are meant to have atleast 14" of W.C. to them. NO MORE, unless it's a special application valve. Not common in furnaces.

    And also, to state the obvious... make sure you have sized the orifices properly, including the pilot orifice if so equipped.

    THERE! I Said it... and I'm Glad.
    Teach the apprentices right... and learn from their questions and ideas.

  6. #6
    Join Date
    Nov 2001
    Location
    Moose Jaw, Saskatchewan, Canada Occupation:Interprovincial Plumber, Commercial Gasfitter Interests:
    Posts
    2,412
    Awww, c'mon, admit it. your'e glad because summer is finally here.
    I love my job, but paydays Thursday

  7. #7
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,400
    Originally posted by rich pickering
    Awww, c'mon, admit it. your'e glad because summer is finally here.
    well, i don't know about that I installed the furnace so i could work on my snowmobiles in comfort. Obviosly once winter is over there will be no need to work on them



    thanks for the info. the unit is a power vented furnace. i don't have the model number with me, but it is 75,000 btu, 80% efficient and has hot surface ignition (no pilot). it is 9 years old. it was pulled from an appartment unit, because the owner wanted all the furnaces replaced. all the other furnaces were from the '70's. this was the only new one. it is in mint condition, not a spec of rust on the heat exchanger.

    the supply house gave me a pack of various sized orifices. i put in the recommended one (according to the included chart) and got the previously mentioned yellow tipped flame. i tried a few larger and smaller orifices and got the same result. i switched back to the recommended one. all 3 flames are exactly the same

    i bought a "universal" propane regulator from the hardware store. i don't know what the output pressure is. it looks like the one on a BBQ Grill and screws onto a propane tank. it is non adjustable. Next time i go to the cabin, i will test the gas pressure to be sure it is correct.


  8. #8
    Join Date
    May 2004
    Posts
    1,308

    Originally posted by rich pickering
    Awww, c'mon, admit it. your'e glad because summer is finally here.
    True enough my brother... anxiously awaiting summer!


    Originally posted by craig1 well, i don't know about that I installed the furnace so i could work on my snowmobiles in comfort. Obviosly once winter is over there will be no need to work on them

    [I rely on my garage furnace to work on my old Harley all winter - And hopefully, come spring... I got all the right pieces on the bike in the right order. ]

    thanks for the info. the unit is a power vented furnace. i don't have the model number with me, but it is 75,000 btu, 80% efficient and has hot surface ignition (no pilot). it is 9 years old. it was pulled from an appartment unit, because the owner wanted all the furnaces replaced. all the other furnaces were from the '70's. this was the only new one. it is in mint condition, not a spec of rust on the heat exchanger.

    the supply house gave me a pack of various sized orifices. i put in the recommended one (according to the included chart) and got the previously mentioned yellow tipped flame. i tried a few larger and smaller orifices and got the same result. i switched back to the recommended one. all 3 flames are exactly the same

    i bought a "universal" propane regulator from the hardware store. i don't know what the output pressure is. it looks like the one on a BBQ Grill and screws onto a propane tank. it is non adjustable. Next time i go to the cabin, i will test the gas pressure to be sure it is correct.
    Yeah, you should be good to go as long as each burner orifice is sized to put out 25,000 btu's each according to the orifice charts...

    You are likely drawing from a Propane bottle? A First stage regulator (rated from 125 psi down to 2 psi) should suffice, but you will need a secondary regulator rated from 2 psi down to 14" of W.C. Even though you are installing it into your Cabin... would be the proper thing to install it all to local code.

    Good luck Craig
    Teach the apprentices right... and learn from their questions and ideas.

  9. #9
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    That is what I was thinking when I was reading down through. I bet he is running that furnace off a 20 #er.

    Around these parts you should have a minimum of 11" W.C. You will never maintain that with that little regulator. When it gets really cold your manifold pressure will drop off and you won't know what the heck you are runing. Next thing you know you'll have a furnace full of soot.

  10. #10
    Join Date
    May 2004
    Posts
    1,308
    Yeah, for certain Benny... Minimum 100# bottle (500 # Pig is common here... unlike Dices 42 # goat)... 14" in... 11 to 10.5 out... NO LESS. Typical winters here are -25 to - 40 on colder times. Propane sometimes does not perform well... but most people get through the winter without too many Carbon-fests.

    Natural gas is so abundant here, only the farming communities away from the larger centers use either Propane or Oil. And although I sit about 800' above one of the worlds largest nat. Gas resources on Earth... still there are many sites that don't have Nat. Gas piped into them. Hence... we do zillions of L.P. furnaces. Of all sizes shapes and descriptions.

    Go figure...
    Teach the apprentices right... and learn from their questions and ideas.

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