Grounding and bonding 2 for the price of one

[codeworks]

i'm used to seeing sprinkler mains used as the water service for the grounding electrode system, hence tieing the gec to it. now, i'm in a new area, working as an inspector, local FM says that this practice is in direct conflict w/ NFPA 13 and wont allow it , i don't have NFPA docs at my finger tips. even if it was in conflict, wouldn't the more stringent code rule apply here? water service is all pex in this area.

numero dos, on a service, conduit runs from main dp to a sub panel, bonding bushings are re3q'd at BOTH ENDS OF THE CONDUIT right? thanks in advance

 

[peach]

If I recall correctly from my Mike Holt Bonding & grounding class, you bond those things that could become energized; I don't know how a fire line would be electrically energized... not having NFPA 13 handy, can't comment if it's in direct conflict with 13. If the FM doesn't allow it, it can't be done.

Numero dos: here, yes .. while I have NFPA 70 here, I'm too lazy this morning to wade thru the articles (just to be referred to another article).

 

[Bryan Holland]

While the NFPA 13 prohibits the underground portion of the metal piping system for fire sprinklers from being used to ground the electric system, the same section clearly states that bonding requirements of the piping system must still be in compliance. See section 10.6.8 of the NFPA 13 and 250.104 of the NEC. (Section 4.14 of the NFPA 780 for an LPS.)

 

[Francis Vineyard]

NFPA 13 permits the sprinkler system to be bonded but not grounded. NPFA 70 requires all metal water piping including metal sprinkler to be bonded per article 250.104(a); even though this can create galvanic corrosion and leaks.

This issue has been brought before the panel several times in the past 2 decades; here’s a link about the panel’s decision I posted on another forum;

Recommendation: ...to add the following new fine print note to the existing

wording of 250.104(B) Other Metal Piping of the 2005 edition of the NEC:

FPN: See Installation of Sprinkler Systems (NFPA 13 Article 10.6.8 and

A.10.6.8) for more information about the fire protection piping systems, which

extend underground.

Panel Statement: A metallic fire sprinkler piping system is metal water piping

system that is covered by Section 250.104(A). Section 250.104(A) does not

differentiate or exclude between the various types of metal water piping

systems that might be present in a building or structure. Section 250.104(B)

covers metal piping systems other than those metal water piping systems

covered by 250.104(A).

Number Eligible to Vote: 15

Ballot Results: Affirmative: 15

http://www.boards2go.com/boards/board.cgi?action=read&id=1292636018&user=vbcoa

 

[fireguy]

What is the purpose of bonding the metal pipe? if bonding can lead to galvanic corrosion, why bond?

What is the purpose of grounding the metal pipe?

What is the difference between bonding and grounding?

I cannot remember when I have seen metal sprinkler pipe bonded or grounded.

 

[Francis Vineyard]

NFPA 70 (of course) determined there is more of an immediate threat to lives from electrical injuries and fatalities than preserving the reliability of the sprinkler system.

NFPA 13 permits bonding “to ensure electrical continuity and the capacity to conduct safely any current likely to be imposed.”

Grounding Electrode System attempts to provide a low-impedance path to the earth from lightning and unintentional contact from higher voltage lines; fire lines are not likely to serve this purpose with the non-conductive coating and isolated joints.

To the untrained eye they appear identical.

 

[GCtony]

So.... assume a typ. metal bar joist building, why bond the piping system when the metal building that is used to support the sprinkler system is already bonded using metalic hangers every 5 or 6 feet. Even if you don't bond the sprinkler system it will still be part of the bond loop and wouldn't corrosion happen anyway. No?

 

[Bryan Holland]

The purpose of GROUNDING is found in Section 250.4(A)(1) of the NEC.

The purpose of BONDING is found in Section 250.4(A)(5) of the NEC.

The AHJ determines when normal installation practices of metallic components creates an "effective" bond, thus eliminating the need for an actual connection via a bonding conductor. Most inspectors are not comfortable & assured the bond is effective if they don't see a physical bonding connection with a conductor and clamp...