Although primarily a design professional, i also do a significant number of fire investigations each year. Several years ago we began seeing residential fires caused by small leaks in the flexible gas lines where they entered the furnace. After the third incident in one year I decided to check my own furnance - and there it was, a hole in the tubing at the point closest to the sheet metal. So this, regardless of the cause, this is no myth!
It is our belief that there are two possible causes for these holes. First, they may be a result of friction, second, they may be caused by arcing between gas piping and the furnace sheet metal during a lightning storm. If the two are are not well bonded sufficient potential difference can develop between the two and cause an arc. In any case, most, if not all the cases which we investigated, were associated with lightning storms.
The moral is, don't use flex except where absolutely necessary. It MUST NOT be used to pass through an opening in the sheet metal of a furnace or other equipment - use a piping nipple where the line passes in. And whereever flex is used, ensure it is properly bonded to any grounded metal close by. W. Thomas Smith January 26 2012, 11:17 pm EST
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