It seems like I have been thinking about National Electrical Code questions for most of my adult life. Whether by mail, phone or text, these questions have stuck with me for the past 40 or more years.

There have been times when I have been on trips overseas with a 12-hour time difference between me and the person calling with a Code question. My ringtone is the Marine Corps Hymn, which certainly gets my attention when it plays at 2 a.m. That has happened on more than one occasion!

My wife doesn’t usually say much when it occurs, but there has been a time or two when I had to play back in my mind the next morning what the question was and how I answered it. Once, I even called the person back to rehash his question and how I answered. Fortunately, and thankfully, my answer was correct, and I did not mislead him.

Quite a few times, I have gotten unique questions that prompt me to write articles for this magazine. I am very thankful for the opportunity to share the questions and answers with the electrical industry.

Grounding and bonding 

One such opportunity came my way a few days ago from a really good friend who teaches at an electrical apprenticeship school. His question was from a former student who called him about a project involving grounding and bonding—a subject near and dear to my heart. The question dealt with grounding electrode requirements for a large electrical service at a new industrial building being built in the Phoenix area.

Section 250.50 states that all grounding electrodes, as described in 250.52(A)(1) through (A)(7) and present at each building or structure supplied by an electrical service, must be bonded together to form the grounding electrode system. Section 250.52(A)(1) requires a metal underground water pipe that is in direct contact with the earth for 10 feet or more to be connected as one of the grounding electrodes.

The new building has a metal underground domestic water supply pipe and a metal underground sprinkler pipe supplying the fire sprinkler system. Sections 250.50 and 250.52 in the NEC do not differentiate as to what metal underground water pipe would be required to serve as one of the grounding electrodes. Certainly, domestic water would, but the NEC is silent about other water supplies.

Fortunately, Section 6.5.1 of NFPA 13, Standard for the Installation of Sprinkler Systems, very clearly states: “In no case shall the underground piping (for sprinkler water supply) be used as a grounding electrode for electrical systems.” 

The enhanced text in NFPA Link states: “The use of underground fire protection piping for electrical grounding increases the potential for stray ground currents and increased galvanic corrosion, which is why such use is prohibited by 6.5.1. Grounding to piping systems that could have nonconductive piping or joints (such as PVC piping) is especially dangerous, since it might not provide the expected ground. In no case should the underground piping be used as a grounding electrode for electrical systems. Electrical equipment should be grounded in accordance with NFPA 70, National Electrical Code.”

Section 6.5.1.1 

In addition, Section 6.5.1.1 states that “the requirement of 6.5.1 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.”

250.1014

The apprentice also was concerned about the requirements in 250.104 for bonding of metal sprinkler water piping throughout the building. The purpose of bonding any metal piping inside the building is to ensure there is a ground fault current path back to the source in case of a fault to ground for any reason.

Back to the question of bonding any metal piping for sprinklers. Sprinkler pipes are often connected together by Victaulic couplings, so sections of metal pipe are electrically isolated from each other. 

Victaulic couplings are components that join mechanical pipes to create a watertight joint. They have a unique construction that includes a gasket, housing and ductile iron. The gasket seals against the pipe, the housing provides space for the seal to flex and the ductile iron absorbs sound.

Since most sprinkler pipes are isolated from any electrical equipment, there is very little chance of the metal piping becoming energized and no reason to comply with 250.104 for bonding.

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