American Fire Sprinkler Association
12750 Merit Dr., Suite 350 * Dallas TX 75251
Ph: (214) 349-5965 Fax: (214) 276-0908
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TECHNICAL UPDATE
OCTOBER 4, 2007
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"Can the electrics service be grounded to the sprinkler piping?"
We have reviewed the 2007 Edition of NFPA 13 as the applicable
Standard. Our informal interpretation is that sprinkler system
piping is not permitted to be used for the grounding of electrical
services, but the system may need to be grounded.
There are two reasons for connecting a conductor to sprinkler system
piping. One is where the sprinkler system is intended to be used as
the "grounding electrode" for the electrical service. This is
prohibited by NFPA 13 section 10.6.8. The other is where the
sprinkler system has the likelihood of becoming energized and
"bonding" is necessary to prevent the occurrence of an electrical
potential difference between the sprinkler system piping and other
conductive material in the building. This bonding requirement is
given in NFPA 70, article 250-104(c). It is important to note here
that if the sprinkler system is not connected to other electrical
equipment, conductors, etc., it is unlikely that the piping will
become energized; thus bonding is not required. Typically the
sprinkler system piping provides the ground for itself. It does not
account for a potential difference between the sprinkler system and
the building systems. FPN (fine print note) to paragraph b indicates
that bonding all piping and metal air ducts within the premises will
provide additional safety. However, NFPA 13 prohibits using the
sprinkler system piping as a grounding electrode. This is to prevent
degradation of the piping resulting from electrolysis. Bonding the
sprinkler system may result in electrolysis and subsequently
degradation of the piping only in the presence of stray or leakage
currents. Examples of these events include high voltage crossover
between high- and low-voltage systems, lightning strikes, voltage
induction, and electrical equipment insulation failures. The degree
to which the piping will degrade is difficult to predict. The exact
effect depends on numerous variables like soil conditions, electrical
system integrity, event voltage and duration, etc. Also, there are
methods to protect the sprinkler piping from stray currents. For
example, installing a dielectric (nonmetallic) fitting between the
overhead sprinkler piping and the underground supply piping will
prevent stray ground currents from entering the overhead piping.
Also, if the dielectric fitting is used, the sprinkler system piping
loses its grounding electrode capabilities. The 2007 edition of NFPA
13 clarified this by adding annex material to section 10.6.8 that
states, "Where lightning protection is provided for a structure, NFPA
780, Section 4.14 requires that all grounding media including
underground metallic piping systems be interconnected to provide a
common ground potential. These underground piping systems are not
permitted to be substituted for grounding electrodes but must be
bonded to the lightning protection grounding system. Where galvanic
corrosion is of concern, this bond may be made via a spark gap." The
intent of this proposal is to identify that a bond is required and
must not be removed and to explain that the purpose of the bond is
not to use the metallic underground piping as an additional grounding
electrode but instead to provide potential equalization. In summary,
using the sprinkler system piping as a grounding electrode is
prohibited. Bonding the sprinkler system piping is only required when
it may become energized. If the electrician is bonding the sprinkler
system to the electrical service ground to provide a safe path of
travel for the electricity should the piping become energized, this
complies with NEC 70 Article 250.104 and does not violate NFPA 13
section 10.6.8. However, if the electrician is using the sprinkler
system piping as an additional grounding electrode, this is a
violation of NFPA 13 section 10.6.8.
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Technical Update is prepared by the Technical Services Dept. of the
AFSA: Vice President of Engineering and Technical Services Roland
Huggins, a PE registered in fire protection engineering; Phill Brown,
a NICET IV certified automatic sprinkler technician and NFPA
Certified Fire Protection Specialist (CFPS) and Tom Wellen, a degreed
fire protection engineering technologist. This is provided with the
understanding that the AFSA assumes no liability for this opinion or
actions taken on it and they are not to be considered the official
position of the NFPA or its technical committees.
Copyright (c) 2007, American Fire Sprinkler Association. All
Rights Reserved
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