Since LP is regulated at a higher pressure than natural gas, you will need a smaller orifice to control the gas flow to the log set. Call the 800 number that came with the instructions to contact the mfg. The orifice change is easy to do. However, more important, you will surely need a safety pilot control valve if it did not come with the natural gas set. Since LP tends to be heavier than air, dangerous concentrations can build up if there is even the slighest leak. Check with your building inspector for proper installation requirements. DON'T TAKE SHORTCUTS! That "sale" set could kill you and your entire family if not installed correctly.