The correct way to bond a parking lot light pole?

[dnbob]

I read the post on the additional ground wire for the pole bases. What is the opinion here as far as how to connect the grounds... If there is a ground rod driven for each pole, should that be the only connection to the pole itself, or should the egc from the panelboard also be connected to the pole.

 

[iwire]

Re: The correct way to bond a parking lot light pole?

Originally posted by dnbob:
If there is a ground rod driven for each pole, should that be the only connection to the pole itself, or should the egc from the panelboard also be connected to the pole.

You must always connect the panel EGC to the pole.

250.4(A)(5)

(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be used as the sole equipment grounding conductor or effective ground-fault current path.

 

[dnbob]

Re: The correct way to bond a parking lot light pole?

Thanks IWIRE, I had recommended that to my boss and he strongly disagreed with me.

 

[iwire]

Re: The correct way to bond a parking lot light pole?

No problem , I have been on jobs that the prints asked for only ground rods at the poles, no EGCs to the panel.

The reason when asked was to keep lightning strikes outside if lightning was to hit the pole.

Even if this was effective lightning protection it is a code violation.

If you only connect the pole to a ground rod and you have a ground fault in the pole the breaker will not open. Also the pole will be 'live' to anyone touching it.

Bob

[ July 25, 2004, 11:30 AM: Message edited by: iwire ]

 

[hurk27]

Re: The correct way to bond a parking lot light pole?

This goes to show that there are many still out there that still do not under stand grounding for fault current. or that lightning traveling miles through open air will not stop because the insulated wires in the pole dont have a ground with them. It will still jump on them and do as much or even more damage.

 

[dcv]

Re: The correct way to bond a parking lot light pole?

dnbob
Why does your boss disagree when the code is so clear?

 

[bphgravity]

Re: The correct way to bond a parking lot light pole?

I also believe the wording, "the sole equipment grounding conductor" in Section 250.4(5) will be removed from the NEC 2005 for the purpose of clarifying that Earth is not an effective ground-fault path and should not even be identifed as an equipment ground (bond).

This may help remove the misconception that a ground rod will serve any purpose in this capacity.

 

[tom baker]

Re: The correct way to bond a parking lot light pole?

"The reason when asked was to keep lightning strikes outside if lightning was to hit the pole." This is only hearsay and there is no documentation or proof it keeps the lightning outside. The only way to protect against lightning on the wiring is with TVSS. If your boss has documentation otherwise Mike Holt and myself would like to see it.
A ground rod may help in lowering the overall resistance. Far better is to tie into the reinforcing steel in the pole base.
No equipment ground is an invitation to an electrocution or shock.

 

[charlie]

Re: The correct way to bond a parking lot light pole?

I believe it will now read, "250.4(A)(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path."

 

[hurk27]

Re: The correct way to bond a parking lot light pole?

Tom

The only way to protect against lightning on the wiring is with TVSS.

TVSS units only protect against the surge caused by a lightning strike on the other side of the transformer. A direct strike to a lighting standard would most likely destroy a TVSS unit on that circuit and still do damage inside the building. A good grounding electrode system with the proper design could limit The amount of current that comes into the building to the point that maybe a TVSS unit would clamp the rest, But in no way could there ever be a guarantee that it would protect everything. The problem is with cost. Most would not want to spend the amount of money this kind of engineering would cost for every pole.
Just a thought.

 

[iwire]

Re: The correct way to bond a parking lot light pole?

Originally posted by tom baker:
"The reason when asked was to keep lightning strikes outside if lightning was to hit the pole." This is only hearsay and there is no documentation or proof it keeps the lightning outside. The only way to protect against lightning on the wiring is with TVSS. If your boss has documentation otherwise Mike Holt and myself would like to see it.

Tom sometimes you need to read the posts with a little more care.

When I said

The reason when asked was to keep lightning strikes outside if lightning was to hit the pole.

I was in no way saying that would work and as a matter of fact I went on to say.

Even if this was effective lightning protection it is a code violation

The fact is the jobs engineer was the one claiming this was effective lightning protection.

[ July 27, 2004, 05:37 AM: Message edited by: iwire ]

 

[pierre]

Re: The correct way to bond a parking lot light pole?

Street lighting poles under the jurisdiction of utility companies usually do not have an equipment ground conductor installed to them.
If this system is not under the POCO jurisdiction, then the NEC is to be followed.

Recently in NY, after 2 people were electrocuted by touching poles, they found more than 700 poles and traffic signals to have been live kind of sad it took 2 innocent people's lives and their families heartache to fix this situation.

Pierre

 

[vicar]

Re: The correct way to bond a parking lot light pole?

If you tie the EG to the Groung Rod at the pole you are creating a grounding potential problem. If the pole becomes energized and the ground rod offers a path of less resistance to ground the CB will never see the ground fault and thereby will not trip. (I have seen this more than once).
An HID ballast by design is to create a ground fault when it goes bad. but if there is no ground path back to the panel the pole will become hot. FYI: If the ballast goes bad and there is no ground path to the supply panel and the lamp is good it will continue to burn until the lamp goes bad. The pole will also be hot as well as the ground around the pole.

 

[don_resqcapt19]

Re: The correct way to bond a parking lot light pole?

vicar,

If you tie the EG to the Groung Rod at the pole you are creating a grounding potential problem. If the pole becomes energized and the ground rod offers a path of less resistance to ground the CB will never see the ground fault and thereby will not trip.

NO! The current is supplied by the breaker so all of the fault current goes though the breaker. The varied and multiple paths back to service grounded conductor does not change this.
Don

 

[tom baker]

Re: The correct way to bond a parking lot light pole?

Vicar I have a question on the following statment
"If you tie the EG to the Groung Rod at the pole you are creating a grounding potential problem. If the pole becomes energized and the ground rod offers a path of less resistance to ground the CB will never see the ground fault and thereby will not trip. (I have seen this more than once)." Was this on a HV system, say 12,500 volts? If not the ground rod resistance would have to be essentially zero to have a lesser resistance than the EG conductor. Also as Don pointed out the fault current wants to go back to the source not to earth.