Sub Panel Ground

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growler

growler

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Atlanta,GA
Looking at a small job for an emissions testing station. Located at what once was a hand car wash at a service station. So it's separate building with a sub panel and no equipment ground ran at the time of install.

Probably be very hard to install a ground conductor at this point and the building is old enough for it to be legal at the time of original install.

After looking a 2017 NEC article 250.32 (B) (1) Exception # 1 the code indicates that it's legal to leave as is. I didn't notice any metal connections between the buildings such as a water pipe.

Any thoughts.
 
Yes the exception would apply to installations installed prior to the adoption of the 2008 NEC. Assuming that the neutral is properly bonded, unless someone is willing to pay to upgrade to the current version of the NEC I would leave it.
 
infinity said:
Yes the exception would apply to installations installed prior to the adoption of the 2008 NEC. Assuming that the neutral is properly bonded, unless someone is willing to pay to upgrade to the current version of the NEC I would leave it.
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Thanks.
 
ActionDave said:
I never saw any reason for the code change in the first place.

As it stands now a service disconnect on a utility pole needs an EGC ran from it for no reason. Waste of resources I tell ya.
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Actually what don't make sense is why was it ok before but now it isn't?

Grounded conductor intentionally carrying current and also bonded to exposed conductive objects will subject those objects to any voltage drop that occurs over the supply conductor. Part of reason we couldn't bond beyond the main disconnect in the first place (feeder or service), but we don't have to worry about it for a separate building supply or a range or dryer..... then it was no longer safe to do with the range or dryer, unless it was existing and compliant at time of install and eventually same thing happened with the main supply to a building that is not service conductors. And the service neutral still can and does raise voltage on non current carrying components to earth because of voltage drop.

What dangers are there sure seems to me they won't care about any date on a code book.

Now you want to upgrade equipment and you sometimes have to figure out how to deal with some of those existing circuits that you might run into even if you are not intending to change anything involving a particular circuit beyond the branch panel it connects to. I think many will agree that house with old fuse panel, 30 amp fuses installed because that is largest that fits the fuseholder, is probably still a big improvement to replace with circuit breaker panel and properly selected breakers (even non AFCI or GFCI) than leaving the old panel as it is, but because the main is too far inside it is no longer the service panel and now you need to replace the range circuit as well. Haven't really run into this sort of issue with additional buildings other than if there is a second path for neutral to follow between buildings.
 
K, I think the difference between grounded single-conductor vs separate neutral/EGC matters more within a premises, where there can be easy exposure to both electrically-grounded and earth-grounded surfaces, which isn't a concern between structures.
 
LarryFine said:
K, I think the difference between grounded single-conductor vs separate neutral/EGC matters more within a premises, where there can be easy exposure to both electrically-grounded and earth-grounded surfaces, which isn't a concern between structures.
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Makes no sense to me, if you are exposed to "true earth ground" and anything connected to the grounded service conductor after it has had some length to develop some potential voltage drop, you are subject to exposure to whatever that voltage drop is regardless if it is at your service entrance or two buildings beyond the service entrance. In fact voltage drop on POCO's MGN can be imposed on your service grounded conductor just as easily, and is one of the reasons shocks and electrocutions sometimes happen to otherwise properly installed equipment at marinas, boat docks, and similar where people in the water are very well connected to true earth potential and then touch something that has just a few volts on it but is connected to the grounded conductor with said volt rise on it via main bonding jumper back at the service. Swimming pools don't have as much issue because we bond everything in and around the pool and we usually only have issues if there is a "hole" in the equipotential bonding system.
 
I was just trying to point out that current requires voltage. Either the system neutral conductor is energized or the earth is.

I know that's obvious. It's gotta be coming from somewhere.

If the OP kills power and the current is still there, ignore it; there's nothing he can do about it.
 
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