Code Stories · PressureTest
Not in facts.json. Verbatim, 248 CMR 5.07(5): "Delete sub-section 7.13.2 and replace with the following: 7.13.2 CSST. CSST systems shall be bonded in accordance with subsection 7.13.1 unless such bonding would be in conflict with manufacturer installation instructions. However, to the extent the manufacturer's installation instructions require additional bonding which falls within the scope of electrical licensure, this code shall not govern such requirements. In such instances, the installation may not be approved by a plumbing or gas inspector unless there is proof that an electrical permit has been obtained to perform such bonding."
Lightning that strikes a building, or strikes near it, can raise nearby metal systems such as wiring, ducts, water pipe and the gas line to very different voltages. CSST has a thin wall.
When the voltage between it and a nearby metal object gets high enough, an arc jumps the gap and can burn a pinhole through the tubing, and the leaking gas can ignite. Bonding ties the CSST to the building's grounding system so its voltage rises and falls with the other metal, which reduces the chance of an arc.
Bonding lowers the risk but does not eliminate it. Research in 2011 concluded that a more complete equipotential approach is needed.
Manufacturers responded with arc-resistant jackets.
Fire Engineering describes the field reports that drove the code change.
Source: https://www.fireengineering.com/fire-safety/new-requirements-for-csst-installation/
The 2009 edition of NFPA 54 adds CSST bonding requirements.
Source: https://inspectapedia.com/Design/National-Fuel-Gas-Code-NFPA_54-2012.pdf
Fire Protection Research Foundation report 'Validation of Installation Methods for CSST Gas Piping to Mitigate Lightning Related Damage' (April 2011).
Source: https://www.subrogationrecoverylawblog.com/2011/04/21/new-report-on-csst/
NFPA 54 2012 moves the bonding connection point.
Source: https://inspectapedia.com/Design/National-Fuel-Gas-Code-NFPA_54-2012.pdf
International Association of Fire Chiefs position on the mechanism.
Source: https://www.iafc.org/about-iafc/positions/position/protection-of-corrugated-stainless-steel-tubing-(csst)-from-lightning-strikes
Mnemonic: 'Bond it so it rises together.' Lightning damage is not about the voltage itself but about the difference between two pieces of metal. Tie them together and the arc has less reason to jump. Picture the result without it: a spark-welded pinhole in a gas line.
The appliance's electrical ground already bonds the gas line.
Do not assume it. MA's rule (248 CMR 5.07(5)) defers to the CSST manufacturer's instructions, and for standard yellow CSST those call for a direct bond to the grounding electrode system. That bonding is electrical work, so the gas inspector may not approve the job without proof of an electrical permit.
Bonded CSST is lightning-proof.
The 2011 FPRF study found end-point bonding alone insufficient for a complete solution. Bonding reduces risk.
Clamp the bond anywhere on the yellow tubing.
No. Manufacturers forbid clamping the corrugated tubing; the clamp goes on rigid pipe or a CSST brass fitting as their instructions specify. The 2012 NFPA 54 wording (metallic pipe or fitting between the point of delivery and the first CSST fitting) is the national rule. MA replaced it with 'follow the manufacturer' (248 CMR 5.07(5)).
CSST (corrugated stainless steel tubing) gas piping systems must be:
A nearby lightning strike can put high voltage on a building's metal systems. Thin-walled CSST can be perforated by arcing between it and other grounded metal, starting a gas fire. Bonding keeps the tubing at the same electrical potential as other metal in the building, which reduces that arcing.
CSST must be bonded because:
CSST's corrugated stainless wall is very thin, and when a nearby lightning strike energizes the building, a voltage difference between the CSST and other grounded metal can arc across it and burn a hole, starting a gas fire. Bonding it directly to the grounding electrode system keeps it at the same potential as other metal so no arc forms.
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