I have a problem with my Vermont Castings Radiance gas vent free fireplace sooting up the inside of the unit. I have tried adjusting the air intake but it either soots up or the flame will go out. Is there a default setting from the factory as to how much the air intake is supposed to be open as far as the collar on the intake tube ? Please reply so that I can get this alternate heating source going again safely. We've had the unit for approximately 5 years and have replaced 2 thermocouples, 1 control switch, and last season the burner assembly was showing cracks so I replaced it at the cost of over $300 at the end of the season as a safety precaution. It's allot financially but when you consider buying another unit at around $2000. It's worth making the necessary repairs or replacements to keep it going. Thank you to all of whom reply.