During the home inspection process, there are findings that consistently draw confusion from real estate agents and home buyers alike. However, no defect seems to be the cause of more recent perplexity than that of missing bonding at gas piping. In response to this, we have authored this blog post in an attempt to clarify not only the necessity of bonding gas pipe systems but also how exactly this bonding is accomplished if not already present within a home.
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Why Bonding Gas Piping is Necessary
Homes are complex environments where seemingly separate systems often interact and impact others. But it doesn’t take a building science geek to understand how homes, energized for lighting and appliances, could become potentially dangerous when the same structure includes a network of natural gas or propane filled metal piping. The interplay between a homes electrical and fuel gas systems, while unintended, are nonetheless not uncommon resulting in electrical faults. Electrically charged gas piping is a hazard not only to whomever may come into contact with it, but can result in explosions through ignition of gas leaks. However, not all dangers are man made; lightning strikes can also energize gas piping resulting in similar hazards. Bonding the piping to the home’s grounding system helps to prevent electrical potential differences between the gas pipes and other conductive surfaces, reducing risks of shock or ignition.
2. Solid Pipe vs CSST Systems
Modern residential gas piping systems can include two primary piping materials, solid pipe and corrugated stainless steel tubing (CSST). While both materials have the same potential for electrical faults or energizing via a nearby lightning strike, differences in how these materials behave under these conditions make them unique. CSST, with a much thinner wall in comparison to solid pipe, has been found to be far more susceptible to physical damage from faults or strikes, resulting in a higher risk of gas leaks and explosions. It is for this reason that unique requirements have been established by the National Electrical Code (NEC) as to how these different systems need to be bonded.
3. Bonding Methods
For systems that only include solid piping material, the methods for bonding are simple. The NEC considers solid gas piping to be bonded in instances where it supplies an appliance on a grounded circuit. However, this is less convenient in older homes that may be employing two-wire ungrounded systems. In these cases, bonding must be made via a grounding conductor, usually a 6 AWG copper wire, clamped to the gas pipe on one end and the homes grounding system on the other. For systems with CSST however, a grounding conductor must always be used. The NEC does not consider a gas piping system to be bonded if it contains CSST where it only supplies appliances on grounded circuits.
4. Fixing The Problem
So, the next time an inspector mentions missing bonding at gas piping you know to take it seriously. However, you also know now just how simply the issue can be remedied. A licensed electrician can make quick and relatively inexpensive work in fixing it. As mentioned before, homes are complex environments where seemingly separate systems can impact each other, and we hope that this article will help you make your home a safer environment to live in.