Sprinkler Main Bonding

D

Dan Mulligan

Member
We have an apartment building with a 1600-amp service. The sprinkler main comes through the slab in steel pipe for 18" and changes to PVC for the rest of the sprinkler piping. The Building Official feels the 18" of pipe needs to be bonded with 3/0. The code he is using is 250.104(B). Does 18" of pipe qualify as a piping system and if it does and needs to be bonded, would it need to be sized based on the service size? The Building Official's argument is there is 10' of pipe underground and if someone were to come in contact with a live wire like an extension cord and the sprinkler main, the bond wire has to be big because the sprinkler main is big.:) We don't think it needs to be bonded at all because it is not likely to become energized. And even if we had a full steel sprinkler piping system the bond would be the equipment grounding conductor for the circuit that is likely to energize the piping system, in this case the 120-volt sprinkler bell.
 
I've seen it enforced both ways. Some inspectors here will require the main line bonded as a grounding electrode others reference a sprinkler code stating the system can " not be used as a ground". Most often the end result here is to bond if it qualifies as an electrode but not as interior pipe bonding due to the type couplings being used between sections
 
Dan Mulligan said:
Does 18" of pipe qualify as a piping system and if it does and needs to be bonded, would it need to be sized based on the service size?
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No, 18" of metal pipe is not a metal piping system so bonding is not required. The question is, is it a grounding electrode? If so then it needs to be connected to a GEC. I've heard sprinkler inspectors say that they do not want the sprinkler pipe used as a GEC and often battle with the electrical inspectors about it. Fact is often both the metal water pipe and the metal sprinkler pipe are connected together in the street outside of the building so it doesn't really matter.
 
NFPA 13 prohibits the use of the underground pipe that supplies a fire sprinkler system as a grounding electrode.
16.16 Electrical Bonding and Grounding.
16.16.1
In no case shall sprinkler system piping be used for the grounding of electrical systems.
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Therein lies the problem. It's a "spitting"contest between inspectors with you in the center.
 
don_resqcapt19 said:
NFPA 13 prohibits the use of the underground pipe that supplies a fire sprinkler system as a grounding electrode.
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But does that mean the piping should not be bonded as oppose to being part of the GEC? How about the bonding of pipes that are run between out buildings?
 
jim dungar said:
But does that mean the piping should not be bonded as oppose to being part of the GEC? How about the bonding of pipes that are run between out buildings?
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The annex in NFPA 13 says you still have to bond the interior sprinkler piping as required in NFPA 70, however in the absence of some type of insulating fitting between the interior and the underground supply piping, the underground piping becomes a grounding electrode.
This issue is rapidly going away as in my area all new underground water piping is non-metallic.
 
don_resqcapt19 said:
The annex in NFPA 13 says you still have to bond the interior sprinkler piping as required in NFPA 70, however in the absence of some type of insulating fitting between the interior and the underground supply piping, the underground piping becomes a grounding electrode.
This issue is rapidly going away as in my area all new underground water piping is non-metallic.
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With metal piping the point is moot and it's funny to see two different inspectors arguing over who's code takes precedence. Often the sprinkler and water main coming in from the street are in the same room connected to the same pipe outside.
 
infinity said:
With metal piping the point is moot and it's funny to see two different inspectors arguing over who's code takes precedence. Often the sprinkler and water main coming in from the street are in the same room connected to the same pipe outside.
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Yes, if there was a real issue, NFPA 13 would require an insulating fitting or pipe section between the metal underground water pipe and the interior sprinkler system piping.
That is the same issue with some water utilities and the American Water Works Association saying not to use their underground water piping as a grounding electrode. They can amend the plumbing codes to prevent the underground water pipe from qualifying as grounding electrode.
 
LarryFine said:
I'm surprised that nobody mentioned gas piping in comparison.
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At least around here, the gas utility was using a dielectric fitting between the underground gas line and the outside gas meter for decades before they started replacing all of the underground gas line with non-metallic piping.
 
infinity said:
No, 18" of metal pipe is not a metal piping system so bonding is not required. The question is, is it a grounding electrode? If so then it needs to be connected to a GEC. I've heard sprinkler inspectors say that they do not want the sprinkler pipe used as a GEC and often battle with the electrical inspectors about it. Fact is often both the metal water pipe and the metal sprinkler pipe are connected together in the street outside of the building so it doesn't really matter.
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So the Inspector is saying it must be bonded not grounding electrode. And he is telling us we need to size it using table 250.122 based on 1600 Amp service size. So even if I agreed that it needed to be bonded I believe the bond wire would be sized based on the circuit that is likely to energize the piping system.
 
don_resqcapt19 said:
NFPA 13 prohibits the use of the underground pipe that supplies a fire sprinkler system as a grounding electrode.
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How on earth did the Corelating Committee let that one get by. That is direct conflict between National Fire Protection Association Standards 13 and 70. I could understand it occurring between 2 or more standard writing organizations but to have it happen within the organization that writes both standards is mind boggling.

At the dawn of the electrical age there was a fear among water utility operators that the use of any underground water piping as an electrical ground would cause galvanic corrosion between the dissimilar metals then commonly used in water distribution piping. A joint meeting of senior members of both the NFPA and the American Water Works Association (AWWA) ended with agreement that there was insufficient evidence that such corrosion was, in fact, happening to warrant concern about the possibility. The 2 organizations made an arrangement to periodically check for the occurrences of such corrosion. I do not know how long that mutual monitoring continued but I have never seen any allegation that such corrosion is happening. For all I know that monitoring arrangement continues in some form today. Now because 2 different NFPA Correlating Committees didn't work together we have a direct conflict between 2 NFPA standards. This raises some interesting questions.

If there is only one water lateral from the utility's water main and the sprinkler piping diverges from that common supply in the served premise is the common water service lateral an "Underground Metal Water Pipe" or is it "Sprinkler Piping?"

I haven't seen the Victaulic pipe couplings used underground on metal pipe but not being a pipe fitter I could easily have missed a common practice. Are there other types of pipe coupling that accidently introduce insulating joints into the water supply lateral underground? If the lateral is free of insulating joints does that make it an "Underground Metal Water Pipe?"

Tom Horne
 
The concept of trying to isolate the sprinkler piping is nonsense. Metal sprinkler piping and electrical metal raceways and EGC's are connected all over the place in a commercial building. So if NFPA 13 says you cannot use the metal sprinkler pipe entering the building as a GEC who cares? Like it or not the underground sprinkler piping is connected to the building GES so the entire concept is just noise.
 
infinity said:
The concept of trying to isolate the sprinkler piping is nonsense. Metal sprinkler piping and electrical metal raceways and EGC's are connected all over the place in a commercial building. So if NFPA 13 says you cannot use the metal sprinkler pipe entering the building as a GEC who cares? Like it or not the underground sprinkler piping is connected to the building GES so the entire concept is just noise.
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The saame with the pool bonding and the language in 250.52(B)(3).
(B) Not Permitted for Use as Grounding Electrodes.
The following systems and materials shall not be used as grounding electrodes:
(1) Metal underground gas piping systems
(2) Aluminum
(3) The structures and structural rebar described in 680.26(B)(1) and (B)(2)
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Dan Mulligan said:
Does everyone agree with the inspector. If you bond the sprinkler main it needs to be a 4/0 based on the 1600 amp service?
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I doubt many would agree.If you are addressing it as a grounding electrode then 3/0 is the largest required (250.66) and if you are bonding it then under '23, 3/0 again is the largest required.
 
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