Is UG fire sprinkler pipe a grounding electrode?

tx2step

Senior Member
250.52(A)(1) says metal underground water pipe is a grounding electrode. Would that also include the UG supply for fire sprinkler piping? I don't see anything that would exclude it.

It looks to me like 250.50 would require it to be used?

Around here (DFW, TX area), I rarely see fire sprinkler piping being grounded or being used as a grounding electrode -- it just seems to be ignored -- is there a reason for that?
 

luckylerado

Senior Member
It must be bonded but it may not be used as a GE. Beware of catholic protection if installed.

NFPA 13

10.6.8* In no case shall the underground piping be used as a
grounding electrode for electrical systems. [24:10.6.8]
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
It must be bonded but it may not be used as a GE. Beware of catholic protection if installed.

NFPA 13

10.6.8* In no case shall the underground piping be used as a
grounding electrode for electrical systems. [24:10.6.8]
so when one code requires something and another code prohibits it, what code wins?

In any case, is there any real difference between bonding it and using it as one of the grounding electrodes? electrically it would appear to be about the same thing.
 

luckylerado

Senior Member
so when one code requires something and another code prohibits it, what code wins?

In any case, is there any real difference between bonding it and using it as one of the grounding electrodes? electrically it would appear to be about the same thing.
NEC does not "Require" it to be used as a GE but does permit it IMO when it meets the criteria of 250.52. Yes, I agree that the electrons do not care if we bond it or call it an electrode.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector
In a much earlier thread on this subject 2013 NFPA 13 A10.6.8.1 was referenced. I'm sure there is a more recent reference but I don't have NFPA13. I have always found the explanation a bit confusing. If NFPA13 forbids the underground sprinkler pipe to be used as an electrode and yet we "bond" the piping in effect it becomes an electrode.
An earlier posts advised the wording was "not to be used as a ground" which could be interpreted to mean as an equipment ground.
Perhaps someone with an updated NFPA13 can provide the exact wording,
 

luckylerado

Senior Member
... the exact wording,
10.6.8* In no case shall the underground piping be used as a
grounding electrode for electrical systems. [24:10.6.8]
10.6.8.1* The requirement of 10.6.8 shall not preclude the
bonding of the underground piping to the lightning protection grounding system as required by NFPA 780 in those cases where lightning protection is provided for the structure.[24:10.6.8.1]
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
NEC does not "Require" it to be used as a GE but does permit it IMO when it meets the criteria of 250.52. Yes, I agree that the electrons do not care if we bond it or call it an electrode.
you know, I never realized that only 7 of the 8 electrodes mentioned are required to be used.

however, I would argue it is a metal undergound water pipe and thus has to be part of the GES.

250.50 Grounding Electrode System. All grounding electrodes
as described in 250.52(A)(1) through (A)(7) that are
present at each building or structure served shall be bonded
together to form the grounding electrode system.
250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
you know, I never realized that only 7 of the 8 electrodes mentioned are required to be used.

however, I would argue it is a metal undergound water pipe and thus has to be part of the GES.
The answer is still "no", see luckylerado's post above.

Below is the text of the Appendix A notes for the 2013 (latest) edition:

A.10.6.8 Where lightning protection is provided for a structure,
NFPA 780, 4.14 requires that all grounding media, including un-
derground metallic piping systems, be interconnected to provide
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 can be made
via a spark gap or gas discharge tube. [24: A.10.6.8]

A.10.6.8.1 While the use of the underground fire protection
piping as the grounding electrode for the building is prohib-
ited, NFPA 70 requires that all metallic piping systems be
bonded and grounded to disperse stray electrical currents.
Therefore, the fire protection piping will be bonded to other
metallic systems and grounded, but the electrical system will
need an additional ground for its operation.


I think if you view the last sentence in A.10.6.8.1 carefully, there is an acknowledgement that the effect may be to cause the system to be part of the GES but if otherwise it were the only means available you would have to add at least one other means. It is, of course, much messier than it seems. For example, municipalities do not maintain separate water systems for potable water and sprinkler water. In fact, depending on the jurisdiction, you may not be allowed to make a separate tap for the fire main. You use back-flow preventers at the service entrance and the domestic water pipe goes that-away while the fire main goes this-away. In practice I believe the idea is don't ground the 100 HP motor to the sprinkler pipe, run the EGC back to the panel or whatever.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
I don't see how the requirement in the NEC to use the underground water pipe as a GE is voided by another code.
Since when is the NEC the "Master Code"? In any event, I'd just bump it up to the Construction Official; that's why he gets paid the big bucks.
 

luckylerado

Senior Member
I don't see how the requirement in the NEC to use the underground water pipe as a GE is voided by another code.
It gets real exciting when the water main and fire main are the same and the electrical inspector and fire inspector are not on the same page.

It has been my limited experience that on new construction the fire main is like a C-900 plastic pipe up to the transition to the ductile iron risor and would not qualify as a GE anyway.

You would think that the NFPA folks would reinforce this in the NEC
 
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