Natural-Gas / Propane Conversion (Input and Orifice)
What changes when an appliance is converted between natural gas and propane: the required volumetric flow for each fuel at the same input (cfh = input / heating value) and the orifice-area ratio from first-principles orifice flow (Q proportional to area x sqrt(pressure / specific gravity)). Field orifice drilling is generally prohibited; install the listed manufacturer conversion kit.
Formula and source
cfh = appliance input / heating value for each fuel; orifice flow Q ~ area x sqrt(pressure / specific gravity), so holding input the area ratio = (cfh_to / cfh_from) x sqrt((p_from / sg_from) / (p_to / sg_to)).
First-principles orifice flow holding appliance input (public); the NG/LP heating values, specific gravities, and manifold pressures are editable defaults.
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