In the past many furnace gas valves were connected directly to the flexible gas line connector. Recently installers have been extending black pipe from the gas valve to the exterior of the furnace cabinet.
The manufacturer of flex line simply says “protect from damage”.
I cannot find specific requirement for black pipe extensions in IRC or UMC.
The City of San Antonio has amended the code with an ordinance that states:
Section 304 INSTALLATION of the International Mechanical Code is amended by adding Section 304.12 as follows:
304.12 Installation at gas valve. Black Iron Pipe shall be installed at the gas valve and extended a minimum of two inches outside the gas furnace and gas rooftop unit’s casing and shall be connected to an approved listed flexible gas connector.
It seems the practice of extending black pipe is AHJ specific and that a flex line routed through a furnace casing to the gas valve may actually be acceptable unless otherwise amended.
See photos. Comments please. I am looking for something in code that is as specific as San Antonio ordinance.
I am researching this because an inspector was disciplined for not requiring the black pipe. The expert against the inspector justified his opinion by simply saying it was improper.