CSST Bonding
CSST Bonding by Tony Leggett
Most of us in the hearth industry work with appliances that need gas lines of sort run. Whether it is iron piping, copper, or corrugated stainless steel tubing, our sales are affected by the cost and simplicity of these gas runs. Corrugated stainless steel tubing (CSST), also known by many as the yellow flexible pipe, has been around for a while and has become very popular among mechanical contractors. It's simplicity and code compliance, with no concealed unions like copper, has made it a popular alternative to copper.
Many are unaware of the fact that there are some discrepancies in National Codes for this type of a gas run. In fact, CSST manufacturers already require that their gas lines be electrically bonded via 6-AWG bonding wire to the building's electrical bond. National Fuel Gas Code and the International Fuel Gas Code also require bonding in the same manner. However, the National Electrical Code allows the use of the equipment bonding conductor on the gas appliance (the third ground wire from a gas-fired appliance) to serve as the bonding wire. At this point, compliance has been relegated to the inspector's opinion, thus leaving many mechanical contractors without a black and white answer on how to bond these runs.
The purpose of bonding these lines is not unfounded. According to UL, there is over $1 billion dollars in structural damage due to lightening strikes in the US annually. Lightning strikes the United States about 25 million times per year with each strike able to carry over 100 million volts. Although there really is no way to completely safeguard a structure from a direct hit, CSST is vulnerable to damage from even a nearby strike. Since most CSST's yellow PVC coating does not insulate well enough to prevent an electrical arc to a nearby combustible and a subsequent hole in the gas line from the arc, the bonding is an attempt to neutralize the problem.
Fortunately, to proactively eliminate the need for the 6-AWG bonding wire and labor cost, some CSST manufacturers have developed a conductive jacket that eliminates the manufacturer's requirement for a bonding wire and labor. Due to the above mentioned variances, it is imperative to ask your local building officials how they enforce the codes on CSST. Since it has become such a major part of our hearth sales, we must also be aware of any impending gas run price hikes, so we can respond proactively.