NEC 250.50 vs NFPA-3 514.4.3.5

[LarryFine]

In the old-but-gutted building I've asked a few questions about recently, that was commercial, but will now be mixed commercial/residential, the domestic water system will be non-metallic from the street in.

However, they are also installing a metallic fire-sprinkler system throughout the building, which 250.50 apparently requires bonding to at the minimum, and possibly even use as a grounding electrode.

However, when I asked the guy from the sprinkler installation company about continuity, he told me that his NFPA-3 book specifically prohibits using this system as an electrode. Quoting from the scan faxed to me:

5-14.4.3.5 In no case shall the pipe be used for grounding of electrical services.

This is followed by what appears to be the equivalent of an FPN:

The use of sprinkler or underground piping for electrical grounding increases the potential for stray currents and increased galvanic corrosion. In addition, the use of non-conductive joints may not provide the expected ground. Electrical equipment should be grounded in accordance with NFPA 70: National Electrical Code.

So, where does this leave us? Either the sprinkler system must be used as an electrode, or it must not be used as an electrode. Plus, if it must not be, is it still required to be bonded, or would that be prohibited, too?

Oh, by the way, there is one more possibly-related quote:

Rubber gasket joints (unrestrained push-on or mechanical joints) are not considered connected electrically.

This tells me to not rely on the system to be electrically continuous. That either means bonding is a non-issue, or that every gasketed joint requires bonding jumpers!

Opinions, please!

 

[tom baker]

The sprnkler piping to the outside is most likely ductile iron with bell/spigot ends, rubber gaskets in the bells. This pipe joint is not electrically conductive and is not a grounding electrode per 250.52(A)(1).

So you don't ground to it, but what about a bonding connection per 250.104?