So a customer asked why his cement fireplace logs were turning black and soot was building up at the top of the decorative stone fireplace face. After all this was a natural gas, direct vent fireplace that had been converted to propane. “Note” – Always use a conversion kit that has been approved by the manufacturer.
Although this type of fireplace can generate some heat, it is intended more for the ambience than for heating purposes. It should be clean burning unlike a standard wood-burning fireplace which creates a lot of smoke and soot. Well the problem was that the entire kit of vermiculite, rock wool and lava rock was mixed together and placed into the burner pan which instantly contaminated the clean burning fuel. This fireplace never had a chance. A classic case of not following the manufacturer’s instructions. Remember these fireplaces have been tested many times before final approval and the manufacturer knows what is best. The lava rock should have been placed around the burner pan and not in it.
The solution in this case is to clean out the burner pan and discard the vermiculite, rock wool and lava rock. These items can then be purchased as a kit or separately from many manufacturers. Place the vermiculite in the burner pan slightly covering the burner tubes. Tear the rock wool into pieces about the size of a quarter and place them on top of the vermiculite. Because the rock wool/vermiculite is intended to simulate burning embers, the pattern is personal preference. Next place the lava rock around the bottom of the fireplace being careful not to spill too much into the burner pan. The fireplace log-sets can be expensive, so to avoid the replacement costs the soot should be cleaned off with an approved product. In fact, depending on how much use your fireplace gets, a yearly maintenance schedule should be adopted to include the cleaning of the log set and the replacement of vermiculite, rock wool and lava rock as needed. This will help to keep the fireplace box and surrounding areas clean of soot. Other contributing factors to the soot problem could be low gas pressure caused by the propane tank needing a refill or improper placement of the fireplace logs. Again, always read the literature that is included with your new appliance and then follow the instructions. It will save you a lot of frustration and ultimately a lot of money.