Burner Conversion

by Robert Brown (rbrown00@uoguelph.ca), HBD #1816, 8/28/95

Brian Pickerell asked about conversion from Nat. gas to propane. From what I understand (haven't done it yet) the difference between the 2 gases, other than their actual makeup, is the pressure at which they are supplied at. The natural gas is supplied (local utility) at a lower pressure than propane from your BBQ tank and regulator. The different gas pressures require different diameter orifices. That's the hole that the gas exits the gas line and mixes with the air, not the multitude of holes (burner ports) that you would find in a ring/star/tube burners business end. The diameter of the orifice effects the turbulence of the gas and how well it mixes with the air. If you contact your local natural/propane gas dealer/fitter they will have a handy chart that will have the correct diameter. They can probably sell you a new orifice (little screw thingy with hole in middle) or you could solder and redrill the old one to the specified size. I think you need a smaller hole for propane but having said that without checking first I am probably wrong.

Brian also asked about mixing the gas with air for combustion. My understanding of this (someone please tell me if I've gone past my limited knowledge) as would be seen in a Burner at home or for beer making is this. Some burners etc are enclosed and utilize a venturi(bernoulli if you prefer) effect to draw the air through an adjustable shutter and into a mixing chamber/tube. Many look like this:

 GV   s\                                   This tube burner (easier to draw)
 I    s  \____________________________     could have a ring, star, or "bowl"
_I____s                               I    burner port configuration
 I     O   mixing tube  o o o o o o o I    s=shutter valve
 -I----s   ____________________________I    GV= gas valve
      s  /                                 O=orifice
      s/                 burner ports
Other burners are simpler and the gas mixes freely in open air (turbulence) and the air gas mix is then contained/directed. My HW burner and simple jet type burners(I believe this is what everyone is referring to) are of this design:

  /     /
 /_____/\         Adj. Flame diffuser                    //----------\\
         \        (steel plate that swings)            //--------------\\
         I I   I                                     //   gas diffusion \\
         I I   I                                          "plate"
         I I   I
           I   I  gas/air directional
           I   I  chamber (tube)
           I   I
                  gas/air mixing
- -----------I-O-I                              ------------------I I-\
gas line       I  Orifice is a hole drilled    gas line              \-
- -----------I---I  in gas tubing cap           ----------------------/
  "jet burner" (without stand)                      Hot Water tank burner
  that I saw at a U.S. home depot
Above are my interpretations of "open air" gas mixing burners. Making a jet burner (or whatever it's called) with the proper orifice, tube, gas mixing space, and flame diffuser dimensions, should be easy enough. Anyone with this type of burner willing to supply the dimensions?

Any gas fitters/engineers with an actual working knowledge are urged to correct me or supply the correct terms. Also, who actually makes the cast iron ring burners used in the various brands of stands? An actual burner could be easily mounted in an inexpensive (home made) stand, Anyone?