electrical protection of csst gas piping systems files/edu_torbin_900.pdf · electrical protection...

Electrical Protection of CSST Gas Piping Systems

Bob Torbin, PE Omega Flex, Inc.


Standard Yellow Arc-Resistant Black


National Standard ANSI LC-1 Performance-based standard Listed system installed in

accordance with manufacturer’s instructions and local code

Updated (2014) include: - Revised installer training - Arc-resistant jackets - Address jacket color

CSST Product Standard


Manufacturer’s Design and Installation Guide

1. Used in conjunction with state and local regulations and codes

2. Defer to Design Guide if no coverage in state or local codes or regulations

3. If conflict exists, then more stringent practice should be applied

4. Frequently updated to reflect changes in codes and technology


Total lightning strokes in US per year: 43,500,000* No house, equipment or material safe from direct lightning strike Most damage from indirect strikes

[*USPLN: 2005-2009]


6

Grounding Electrode

Underground Pipe

Electric Power Line

Metallic Appliance Vents


Average annual number of U.S. home fires by cause*: - All 1 & 2 family house fires: 374,000 - All fires caused by electric distribution: 22,400 - All fires caused by lightning: 4,300 - All fires caused by fuel gas: 3,280 (1050 leaks & breaks) - Fires caused by lightning/wires: 280 - Fires caused by lightning/fuel gas: 188

Lightning damage to gas piping is an uncommon event compared to other causes of fires.

[* NFPA Statistical Data/NFIRS]

Residential Fire Statistics*


What are the root causes?

Changes in house construction/size/location Loss of metal piping

Loss of copper wire for communications

Loss of metal conduit for electric wiring


Metallic appliance flue (in stead of

brick/clay chimneys) which rise above the roofline. Metal vent acts like lightning rod not directly connected to the electrical grounding system.

Unintended Consequences


Lightning does not discriminate. It seeks all pathways to ground. It will damage all mechanical/electrical systems.


Arcing damage impacts all metallic systems including wiring and all gas piping materials.

Damage not due to lightning induced voltage levels, but due to large differential in voltage potential.


• Lightning energy enters house and all metallic systems

• Unequal bonding of metallic systems

• Close proximity of metallic systems • Sufficient energy to jump air gap,

overcome dielectric strength of CSST jacket and burn through CSST wall

• Gas flame near combustible material

Requirements for Arcing Fire


Model Code and Standards

• National Electrical Code (NFPA 70) • International Fuel Gas Code • Lightning Protection Std. (NFPA 780) • ANSI Standards

• 50 states and 50 codes

No requirements for lightning protection


Nationally recognized standards No requirements for lightning

resistance No prescribed national test method

for lightning resistance Same for mechanical and electrical

equipment

Product Standards


• Underground metallic piping not used as grounding electrode

• Require dielectric fitting before POD • No grounding/bonding required on underground piping or container

15

NFPA 58 (2011 and 2014)


NFPA 70-Equipment Grounding Conductor

EGC sized to protect against ground faults

Bonding wire sized based on size of branch circuit

12 AWG wire not designed to handle large DC voltage associated with lightning


NFPA 54 (2009 & 2012) – Electrical Bonding*

CSST. CSST gas piping systems shall be bonded to the electrical service grounding electrode system. The bonding jumper shall connect to a metallic pipe or fitting between the point of delivery and the first downstream CSST fitting. The bonding jumper shall not be smaller than 6 AWG copper wire or equivalent. Gas piping systems that contain one or more segments of CSST shall be bonded in accordance with this section. * More changes coming in 2015 edition


1) Equi-potential bonding of all metallic systems

2) Direct bonding of piping to grounding electrode system Downstream of point of delivery Single point of attachment required Bonding clamp on pipe or fitting and not on CSST tubing Conductor at least 6 AWG copper Conductor as short as practical Connect to grounding electrode system per NEC

CSST Manufacturer’s Bonding Requirements


Bond at the most convenient

location within the house with the shortest practical conductor length.


Bonding Gas Systems After “Point of Delivery”


Bonding Clamp* Attachment

* Bonding Clamps listed to UL 467


Bonding Requirements

Gas piping systems that contain one or more segments of CSST shall be bonded.


Bonding Connections

Gas piping shall not be used as a grounding electrode


Bond Connection to Grounding System


Bond to Intersystem Termination or Panel Box


Bonding Conductor Sizing

Conductor at least 6 AWG copper or 4 AWG aluminum Conductor single or multi-strand Conductor length and gauge are inter-related, but length is not specified in the NEC


• On new installations, bonding should be performed (and permitted)

by on-site electrical contractor.

• On retrofit job, plumbing contractor should pull both plumbing and electrical permit, but get electrical contractor for bonding

• Some jurisdictions do not restrict who does bonding

Who Does the Bonding?


Avoid Direct Contact with Metallic Systems


Ground Connection of Grounding Electrode(s)

Earth resistance reading at ground rod must be less than 25 Ohms or a second driven rod must be installed. Earth resistance can vary based on soil type, season and type of electrode.


Lightning entry point Equi-potential bonding Bonding location Length of conductor Proximity of other pathways Grounding electrode system Code requirements

Bonding Effectiveness Factors


Bonding Effectiveness Research

• Bond is effective (no arcing damage to CSST) • Indirect and partial direct lightning strikes • Lightning energy 8/20 and 10/350 up to 10kA • No damage for long conductors (up to 150-ft) • No arcing for shorter conductors (< 75-ft) • Lightning entry point varied • Clamp location not significant factor • Multiple bonding not justified for SF house


Revised bonding for CSST - limit conductor length: 75-ft vs 150-ft vs unlimited - no need multiple clamp locations - clamp location anywhere along piping system - bonding additional grounding electrodes - bonding to lightning protection system

32

NFPA 54 (2015 in process)


Arc-Resistant Jackets

• Conductive jacket • Arc energy absorbed • Listed to ICC bench standard • Protection up to 5 Coulombs

33

WARDFLEX II


Arc-Resistant Protective Jacket is Fully Tested*

[* No product is immune from lightning damage.]

0.1

1

10

100

1000

0.00001 0.001 0.1Arc

Char

ge in

Cou

lom

bs

Duration of Arc in Seconds

Arc-Resistant

Yellow CSST


CSST Safety Campaign

• PERC gas customer mail insert • SFM public service announcements

• Partnership with NAIC • AHRI Model legislation - Home Inspectors

• PERC DIY Campaign


www.CSSTSafety.com

http://www.csst.com/


CSST systems used safely for 24 years according to manufacturer

instructions and code requirements Training and inspection are essential elements of safe installations Lightning affects all metallic systems in the house Direct bonding is effective and will reduce impact of lightning strikes

on gas piping system. Arc-resistant CSST products exist equivalent to bonding Gas industry seeking updates to building codes and standards CSST industry working on public awareness

Summary

Questions

Bob Torbin Omega Flex, Inc. [email protected]

electrical protection of csst gas piping systems files/edu_torbin_900.pdf · electrical protection...

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