National Electrical Installation Standards

Standards as High as Your Own

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Monday, May 17, 2021

Question:

Hello,

When replacing a residential service panel, local code requirements are to bond water lines & now gas lines. In older homes where HVAC units are installed with only two insulated conductors it poses a hazard to homes that have gas water heaters. I service residential properties mainly and have had 3 separate occasions where home owner stated their AC went out them their water heater blew up! That’s right, blew up! The problem was a short at the HVAC unit on the roof, where the short traveled the HVAC’s gas line to the water heater and then through the water heater gas over to the cold water pipe that was grounded and exploded the flex water pipe. Had the gas line been bonded a more serous explosion may have happened. Question is, any changes expected to bonding gas lines coming soon. Some local jurisdictions are no longer requiring it, or maybe only after a certain year. Thanks for your help.

Richard Donaldson

A

Answer:

Greetings Richard,

There's a lot going on in your question. The events described are beyond the minimum requirements for bonding other metal piping systems that are likely to become energized. We cannot address the reasons for these problems. To answer your question, the NEC continues to require bonding of other metal piping systems as stated in Section 250.104(B). It is our understanding that there are no public inputs to remove the gas piping system bonding rules from the NEC. NFPA 54 the National Fuel Gas Code also provides installation information, including bonding of metal gas piping systems in addition to the information provided in NFPA 780 the Standard for Installing Lightning Protection Systems.

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