The distance depends on whether you are using High Pressure Propane, Natural Gas, or Low Pressure Propane:
► The optimum distance is 10" using High Pressure Propane, (but a JetC10 is placed at 8").
► The optimum distance is 6" using Natural Gas, for all jet burners.
► The optimum distance is 8" using Low Pressure Propane, (but a JETC10 is placed at 6"). To get adequate volumes of gas in this case you must pipe the Low Pressure propane to the burner in the same size pipe ID as the entry pipe fitting ID on the jet ring burner. In addition, it is recommended to use a twin stage low pressure regulator with a larger gas outlet on the regulator. Since the pressure is preset, all you can do to insure adequate volumes of gas is to make sure you use large enough pipe or hose to carry the required volume of gas to the burner.
Jet Ring Burners are designed to give optimum performance when the spacing from the tip of the jets to the heated surface is correct. Call 713.222.6095 if further information is needed.