Hot Lighting Poles

[tom baker]

I recieved the following from a technican at a city transportation department. I am hoping the forum users can help with an answer:
"We have ?hot poles? with a reported amperage of 32 amps going to the base. The supply voltage is 120 volts. The steel poles are not bonded and are fed with a 60 amp fuse.

We are looking for a method of quickly testing them without using a meter and grounding rod. Any suggestions?"

 

[websparky]

Re: Hot Lighting Poles

Hi Tom,

If the person means "how to easily test to see if there is a problem", then I would suggest a "glow stick" type tester. Usually the ones that are less expensive will pick up lower readings. They can be attached to a wooden pole to extend the reach from a vehicle as they drive by.

Hope that's what he meant!

 

[hurk27]

Re: Hot Lighting Poles

By Tom: We are looking for a method of quickly testing them without using a meter and grounding rod. Any suggestions?"

Yep: Just take off your shoes and socks and grab the pole?

Of course you know there should be an EGC ran to each pole.
Anytime a system is found installed that does not conform to safety, it should be corrected, and it sounds like they just want a quick fix, (or should I say "Patch") That's going to get people hurt or worse like Mike has sent out in the news letters Killed!

[ August 31, 2004, 11:41 PM: Message edited by: hurk27 ]

 

[ryan_618]

Re: Hot Lighting Poles

I wonder if they used a ground rod instead of an equipment ground for the fault clearing path.

 

[hurk27]

Re: Hot Lighting Poles

Tom have you found anything else out?

 

[pierre]

Re: Hot Lighting Poles

Tom
I spoke to a utility rep from Con Edison today. Con Edison is the POCO that was responsible for the two deaths related to manhole covers and lighting poles.

They tested tens of thousands of poles and manhole covers with 'volt tic' handheld noncontact testers, just as Dave explained.

To resolve the manhole cover grounding, they drive gound rods in the bottom of the manhole and drill a lug in the cowling.

To resolve the lighting poles, they drive ground rods at every pole as per NESC.

Pierre

 

[don_resqcapt19]

Re: Hot Lighting Poles

Pierre,

To resolve the manhole cover grounding, they drive gound rods in the bottom of the manhole and drill a lug in the cowling.
To resolve the lighting poles, they drive ground rods at every pole as per NESC.

Neither one of those "solutions" will help prevent shock unless you are dealing with high voltage distribution where the grourd rod can cause the OCPD to open the circuit. The hazard will exist as long as the fault exists. Anyone touching the pole or cover while the fault exists will still be subjected to shocks unless he or she is standing on the grounding electrode. An EGC back to the source grounded conductor is required on lower voltage systems to prevent the hazard.
The original question specifies a voltage of 120 volts....an EGC is the only way to solve the problem....a grounding electrode will not help.
Don

[ September 02, 2004, 10:27 PM: Message edited by: don_resqcapt19 ]

 

[charlie b]

Re: Hot Lighting Poles

I have to admit that it was a Mike Holt seminar on grounding and bonding that finally woke me up to what I now see as a simple fact: that current has no interest in planet Earth. It has no objection to taking unfair advantage of the planet?s existence, to fulfill its evil schemes (i.e., to find its way back to the source). But as Don says, the planet is of little use to current, when the current is being driven by a 120 volt source. It will still take advantage of all available paths, and would not hesitate to go through any human who happens to be in the way. The problem is that the amount of current that follows dirt on its way back to the source is too small to trip the breaker. Sadly, however, it is enough to give the human a bad day.

Like Don said, a ground rod is no answer. You need a low resistance path for the fault to follow; you need an EGC.

 

[charlie]

Re: Hot Lighting Poles

The problem is probably poor maintenance on the part of ConEd and now the regulatory commission is involved. The regulatory commission doesn't normally have knowledgeable members so they put in requirements that do not make sense but make the public feel better.

The NESC requires the metallic parts of street light columns to be bonded to the MGN and no EGC is required to be installed. If properly installed and maintained, this is a good system. If it is not properly installed and maintained, it becomes a killer and fodder for Joe's pictures (rightly so, I might add).

 

[hurk27]

Re: Hot Lighting Poles

By Charlie: The NESC requires the metallic parts of street light columns to be bonded to the MGN and no EGC is required to be installed.

This is one thing that I have yet to get answer that make any sense?

Why can the NESC allow the MGN (main grounded neutral) be used for bonding of metallic poles. when yet the NEC says using a neutral as a bond is a hazard after the main service disconnect? ( one of the main reason's wiring of dryers and ranges was changed to 4-wire)

It will be safe as long as voltage drop is kept to a bare minimum and yes it will fault the OCPD if one is installed, But if the supply end of this conductor looses connection this pole will be hot. This seems like a big chance that the power company's are taking to keep a installation's cost down.

And I agree that if this supply could be installed where there would be no chance of the neutral ever failing (like irreversible welded connections) then I'd be all for it. But I have seen too many MGN connections that have failed and all it takes is one when a child is touching one of these poles.

I know this has been the practice for along time. But is it safe? and if it is then why does the NEC not allow it?

Just trying to learn

 

[don_resqcapt19]

Re: Hot Lighting Poles

Wayne,
If the feeder to the pole is not in metallic conduit and not EGC was pulled, then 250.32(B)(1) would permit the use of the grounded conductor for grounding of the pole as long as a grounding electrode system was installed at the pole.
Don

 

[hurk27]

Re: Hot Lighting Poles

Don shouldn't that be 250.32(B)(2)?
And is a pole mounted light a structure?
410.15(B)(5) seems to still require a seperate grounding conductor?

And if this covers pole mounted fixtures then this would cover a common pole light that we install in a front yard of a house, as there is nothing in the NEC that says there is any different grounding requirments for a shorter pole on this subject.

I might be wrong but I just don't see it. But I do see the danger of wiring a pole light like this.

 

[charlie]

Re: Hot Lighting Poles

Wayne to start with, I shouldn't use acronyms without indicating what they mean, sorry. MGN means Multi-Grounded Neutral and electric utilities have used them for years.

The problem is not the MGN type system, it is maintenance and installation methods. I don't recall hearing about any hot columns on our system but, I assure you, that doesn't mean that we have never had that problem.

For the most part, we now use non-metallic columns that don't require grounding. In the past, we used steel and later aluminum columns. Our standards called for the neutral conductor from the feed to extend through the neutral connector block and land on a lug that is factory welded on the interior of the column. Our field procedures called for that connection to be checked every time the hand hole cover was removed. No ground rods are installed; however, to concrete bases we used to use were made to our specifications. A coil of #6 solid bare copper wire was placed in the bottom of the form with heavy felt paper over it and the tail wrapped around one of the anchor bolts three or four times on its way to the center of the bolt circle. After the base was set and the column installed, the tail was connected in the same block.

The bottom line answer to your question is that the MGN system works with proper maintenance.

 

[don_resqcapt19]

Re: Hot Lighting Poles

Wayne,
Yes, it should have said 250.32(B)(2), not (B)(1).
As far as the pole being a structure, CMP4 put Exception #4 to 225.32 into the code because a light pole is a structure and without the exception each light pole would be required to have a disconnect. I don't see a requirement in 410.15(B)(5) to provide an EGC to the pole, only a requirement to bond such a conductor to the pole if one is installed.
Don

 

[pierre]

Re: Hot Lighting Poles

Don
Ah ... I did not see the voltage rating! That should slow me down some as I read future posts

Pierre

 

[hurk27]

Re: Hot Lighting Poles

Thank's Charlie as I agree if the connection is checked often enough that the connection would not fail but many hand holes don't get opened enough if any after the pole is installed as most maintenance is only done up at the fixture. A dielectric grease would insure that the connection would last longer but I have seen these connections be subject to moisture and after a few years break down. This would leave a metal pole hot to the touch. While there's no argument that wood or fiberglass poles doesn't need a EGC, But I think a metal pole should have one. If only for the safety of it. we only hear of the ones that have injured or killed someone but I'll bet there is many that have not been reported.
As I said in another post It is sad that it will require a few lives to be taken before a practice like this changes.

Again Don I think you meant the #3 exception? Not #4

Don the way I read Exception #3 to 225.32 is this only allows the disconnecting means for poles used as lighting standards shall be permitted to be located elsewhere on the premises. It still needs a disconnect?

V. Grounding
410.17 General.
Luminaires (fixtures) and lighting equipment shall be grounded as required in Article 250 and Part V of this article .

But I don't see any exceptions in 410.17 that would allow a pole mounted fixture that is fed from the load side of a service to be grounded from the neutral? With what your saying is that we only have to run a two conductor out to a post light and bond the neutral to the pole? I can't see that being allowed? There must be a EGC ran.

 

[charlie]

Re: Hot Lighting Poles

Wayne, it depends on how the maintenance manuals are written and how the trouble men were trained. When working on a column, the fuse is supposed to be checked first along with all the connections in the hand hole if it is out of service. If it is in service, the trouble man will go straight to the fixture and trouble shoot there. That will include checking all the connections at the fixture (BTW, the neutral grounds the fixture again at that location on our system).

 

[iwire]

Re: Hot Lighting Poles

Originally posted by hurk27:

V. Grounding
410.17 General.
Luminaires (fixtures) and lighting equipment shall be grounded as required in Article 250 and Part V of this article .

But I don't see any exceptions in 410.17 that would allow a pole mounted fixture that is fed from the load side of a service to be grounded from the neutral? With what your saying is that we only have to run a two conductor out to a post light and bond the neutral to the pole? I can't see that being allowed? There must be a EGC ran.

Wayne I would say 250.32(B)(2) is the exception that would allow a two wire feed to a post light in your front yard.

I see nothing in 250.32(B) that limits this to only feeders, it uses the term supply conductor and in 250.32(A) they use the words "feeder(s) or branch circuit(s)"

Of course now you need a ground rod at the post light not that I see what that will do for safety.

 

[pierre]

Re: Hot Lighting Poles

For premises wiring:
410.18(A), .20, .21 should supercede 410.17.

Also referring to 250.4(A)(5) the last sentence would preclude the use of 250.32(B) as using a ground rod at premises lighting pole installations, without installing an EGC.

250.3 mentions other Articles that modify or are in addition to the requirements of 250, of which is listed Art 410.

 

[iwire]

Re: Hot Lighting Poles

Originally posted by pierre:
For premises wiring:
410.18(A), .20, .21 should supercede 410.17.

All of those requirements will be meet.

Originally posted by pierre:
Also referring to 250.4(A)(5) the last sentence would preclude the use of 250.32(B) as using a ground rod at premises lighting pole installations, without installing an EGC.

Not exactly, we are not talking about using the ground rod or the earth as the ground fault path.

What we are talking about is using the grounded conductor as the grounding means which is allowed for a separate structure (if we like it or not) by 250.32(B)(2)