Grounding Site lights

[George Stolz]

Cwolf, welcome to the forum.

...anyone coming into contact with this pole would become the path of least resistance to ground.

That statement denotes a misunderstanding, so I would like to address it. Electricity is seeking any path back to it's source, not the path of least resistance to ground. If you drive ground rods, connect them to the pole, and leave the pole unbonded, then both the rods and people will be conducting current. Driving a rod does not cause the current to take solely that path. It will take every path.

However, by unbonding the neutral from the pole and driving individual ground rods at each one, you have lessened the possibility of someone coming into contact with an energized pole.

Not unless several rods are driven about 4' deep, and then used as a picket fence.

 

[bdarnell]

Not to pile on, but here is an excerpt from an article written by Mike Holt in August of 2000:

The National Electrical Code does NOT require a ground rod at metal poles.

A ground rod at a pole will NOT clear a line-to-ground fault for systems that operate at less than 600 volts.

A ground rod at a pole will NOT reduce the touch potential from the metal pole to the earth from a line-to-ground fault.

A ground rod is NOT required at a metal light fixture pole by the Lightning Protection Institute http://www.lightning.org.

A ground rod is NOT required at a metal light fixture pole by the Lightning Protection Standard (NFPA 780) http://www.nfpa.org.

A ground rod at the metal pole does NOT reduce damage to the fixtures, lamps, and the pole wiring, because the lightning traveled through the equipment on the way to the earth.

A ground rod at a metal pole does NOT protect the concrete foundation that supports a metal pole from lightning damage. If there were true, then electric utilities would never use concrete poles to support overhead wiring.

A ground rod at the metal pole does NOT protect the circuit wiring and equipment in the building from lightning damage (open back door). If you want to protect the circuit wiring in the building, then surge protection should be installed on the circuit conductors that go outside to the metal poles.

And I also say, welcome to the forum cwolf

 

[cwolf]

Let me clarify my last posting. I misstated my point. If the ballast in one of these poles shorts out with the neutral bonded to the pole, if the neutral back to the source is broken, then the pole has the potential to become energized. By unbonding the neutral at the pole, (the neutral still being a continuous grounded conductor back to the source) that potential is avoided. However, I agree that there is no protection from a ground-fault at the pole. This is not a fix, but the situation was definately not made worse by unbonding the neutral at the pole. Again, in my opinion, the way to fix this situation is to install a grounding conductor.
Thanks for the welcome, by the way.

 

[mattyb]

I believe the million dollar question with this issue is; do you consider a light pole a structure? A light pole is a fixture, or by code definition equipment, not a structure.
Article 100 - Structure. That which is built or constructed.
Article 100 - Equipment. A general term including material, fittings, devices, appliances, LUMINARIES (FIXTURES), apparatus, and the like used as a part of, or in connection with, and electrical installation.
NOTE: Fixtures are not listed under the definition of Structure, but under equipment.
So if a light pole (Fixture) is not a structure the original installation was not a legal installation under code section 250.32(B)(2)!!!!!!!!
I certainly would not bond the neutral to the frame of a box in an old home which did not have ground wires pulled to the receptacles so why would you do it at a light standard?
I can understand using the code section 250.32(B)(2) when running a new feeder to a separate building where you have another main disconnect and re-establish your neutral to ground bond at that main, but not with site light fixtures.
I know that by removing the neutral bond from the pole did not resolve the problem; and I made the customer aware of this as well, but I surely don't believe we made the problem worse by unbonding the neutral from the pole. By having the neutral bonded to the pole the pole itself now becomes part of the grounded circuit carrying the unbalanced load of the ballasts. Anyone coming in contact with the pole, and is in contact with the earth has a great potential of getting shocked from the pole.
The only way to properly fix the problem is to add an equipment grounding conductor.
My argument is with the engineer that designed this "unique" wiring system. I am saying that it was not done to code originally and must be changed!!!!

 

[don_resqcapt19]

cwolf,

This is not a fix, but the situation was definately not made worse by unbonding the neutral at the pole. Again, in my opinion, the way to fix this situation is to install a grounding conductor.

Yes, it was made worse. If the grounded conductor remains bonded to the pole you have to have two faults to energize the pole. An open grounded conductor and a fault at the pole. When you unbond the grounded conductor, a single fault at the pole will energize it.
Don

 

[don_resqcapt19]

Matt,
There is no question that under the rules of the NEC that a light pole or standard is a structure. At least the CMP thinks it is a structure, because if it wasn't a structure, there would be no reason to have Exception #3 to 225.32.

That being said, there is more here than we have been told about. The fact the the grounded conductor is bonded at the pole does not, in its self, create an energized pole under normal conditions. If people were getting shocked, there is another problem that the bonding did not create.
Don

 

[iwire]

I believe the million dollar question with this issue is; do you consider a light pole a structure? A light pole is a fixture, or by code definition equipment, not a structure.

Matt regardless of your feeling that a light pole is not a structure the NEC does consider it a structure.

Items can be more than one thing at a time.

As an example a receptacle outlet is by definition equipment and a device.

Section 225.31 requires a disconnecting means at every separate structure or building.

Section 225.32 tells us that disconnecting means will be at that separate structure or building.

Now when you look at the exceptions under 225.32 and you find that they allow the disconnecting means for light poles and sign poles to located elsewhere.

Now if the NEC did not consider a light pole a structure there would be no need for the exception at all.

 

[mpd]

I still say the bottom line is you cannot bond a light pole with the grounded conductor, call it whatever you want.

 

[iwire]

I still say the bottom line is you cannot bond a light pole with the grounded conductor, call it whatever you want.

mpd if you go back a bit I said that I thought you found a section that seems to make this a violation.

I am not sure the section you noted does that.

Also there is still the question of what code these poles are subject to.

They may not be subject to the NEC at all.

 

[mpd]

iwire

if these poles are utility owned poles I agree this is not a NEC issue, but if the original post was from an electrical contractor I would assume they are privately owned and it would be a NEC issue, what has you on the fence with the section I quoted?

 

[hardworkingstiff]

Yes, it was made worse. If the grounded conductor remains bonded to the pole you have to have two faults to energize the pole. An open grounded conductor and a fault at the pole. When you unbond the grounded conductor, a single fault at the pole will energize it.
Don

I would think if the grounded conductor is bonded to the pole, and the grounded conductor becomes open between the pole and the power source the pole would then become energized with no additional faults.

 

[mpd]

I feel the same way, if you lost the neutral between poles, the pole would become energized and nothing would trip

 

[cwolf]

Whether or not this is an NEC issue or not is not the question. It is obviously a safety issue. There's no argument that more needs to be done to remedy this situation. The original problem arose because people were getting "nailed" off of these poles at numerous locations across the state. These locations were all wired the same way. Two circuits are sharing a neutral. The unbalanced load between the two circuits was being carried back through the neutral. When someone walked up to the pole and touched it, they were becoming a paralled load to the pole. Thus getting shocked. That situation was alleviated by unbonding the neutral from the pole. In-line fuses were installed at every pole to isolate it in the event of a short in the ballast. However, the problem still at hand, is the potential for a ground-fault at the pole.

 

[mpd]

cwolf

if this is a NEC issue then you are also in violation for the work your company did, was this reported to the AHJ? is the plan to leave the poles ungrounded? are the poles still in service?

 

[jtester]

The original problem arose because people were getting "nailed" off of these poles at numerous locations across the state

Nailed in this instance, you defined as feeling a shock.

However, the problem still at hand, is the potential for a ground-fault at the pole.

This wasn't a problem before. It is one that was created by unbonding the neutral, and it could result in fatality, not shock.

 

[cwolf]

Yes, the AHJ was consulted before any modifications were made. Jtester, is it your recommendation that the neutral be reterminated to the poles and left alone?

 

[iwire]

Yes, the AHJ was consulted before any modifications were made. Jtester, is it your recommendation that the neutral be reterminated to the poles and left alone?

I think you have been missing what many of us have been saying.


1)Using the grounded conductor for grounding the pole is not a good design and it may possibly be a code violation.

2)Your removing the bond has made a poor situation worse.

(And a direct violation of the NEC, if someone gets hurt now you will be subject to civil and possible criminal action regardless of your good intentions and the AHJs blessings.)

3)The bond should be reconnected until such time a true EGC can be provided.

4)The reason for the grounded conductors elevated potential to ground should be located and corrected.


IMO It does sound like an open neutral somewhere in the circuits as the grounded conduct should not be at that much difference of potential from earth assuming a fairly balanced load.

 

[iwire]

iwire

if these poles are utility owned poles I agree this is not a NEC issue, but if the original post was from an electrical contractor I would assume they are privately owned and it would be a NEC issue,

As these are rest areas they may in the 'no mans land' that traffic control devices apparently operate in.

what has you on the fence with the section I quoted?

:lol:

Yeah I am balancing on the fence on this one. :lol:

410.15(B)(5) Metal raceways or other equipment grounding conductors shall be bonded to the pole with an equipment grounding conductor recognized by 250.118 and sized in accordance with 250.122.

The way I see it the bonding jumper from the grounded conductor to the pole is the only section of conductor that must be a conductor recognized by 250.118.

Lets say the circuit to the pole was just the two circuit conductors in a metal raceway, 410.15(B)(5) requires the bonding jumper from that raceway to the pole to be recognized by 250.118.

Now exchange that metal raceway for the grounded conductor allowed by 250.32(B)(2) and the result is the same.

JMO, and I may be reading it wrong myself.

Bob

 

[don_resqcapt19]

I would think if the grounded conductor is bonded to the pole, and the grounded conductor becomes open between the pole and the power source the pole would then become energized with no additional faults.

Sorry guys...I am wrong on this one....You are correct a sngle open neutral energizes the pole.
Don

 

[don_resqcapt19]

Two circuits are sharing a neutral. The unbalanced load between the two circuits was being carried back through the neutral. When someone walked up to the pole and touched it, they were becoming a paralled load to the pole. Thus getting shocked. That situation was alleviated by unbonding the neutral from the pole. In-line fuses were installed at every pole to isolate it in the event of a short in the ballast.

There is still some other reason for the shocks. The only voltage between earth and the pole with the neutral bonded to the pole would be eqaul to the voltage drop on the grounded conductor between the main bonding jumper and the pole. If everything else is ok on the circuit, this voltage will be too low to feel.
Don