The site lighting at a majority of the Rest Areas and welcome centers in PA have been wired using a multi circuit branch circuit. They were installed using a three wire direct buried cable between the lights. (Two hots and one neutral). NO EQUIPMENT GROUND WAS INSTALLED. They had the neutrals bonded to each pole and each ground rod at each pole. The engineer is arguing with me that this is a legal installation according to 250.32(B)(2). Our company was called to inspect the wiring due to people complaining that they where getting shocked off the poles. "DUH" We eliminated the bond between the neutral conductor and the poles and ground rods and told them that was a temporary fix, and that they had to either install an equipment ground or change the circuit and ballasts to 480volt 1phase and then the neutral could be changed to an equipment ground. Could someone please clarify that what we did and are telling him is correct?
Grounding Site lights
- Thread starter mattyb
- Start date
- Status
bdarnell
Senior Member
- Location
- Indianapolis, IN
- Occupation
- Retired Engineer
Believe it or not, the engineer may have gotten either an opinion from someone in authority or from an actual AHJ who determined that a lighting standard is a "structure". I'd argue that a lighting pole is not a "structure" as defined by the NEC as it is not "built" or "constructed". It is "erected".
As to whether your solution is viable, I'd say that it would be if you can change the ballasts to 480 V and re-identify a conductor as an EGC (provided it is #4 or larger).
As to leaving it that way "temporarily", I wouldn't have if I was taking ownership of it. I would have locked the circuit out. Just MHO.
As to whether your solution is viable, I'd say that it would be if you can change the ballasts to 480 V and re-identify a conductor as an EGC (provided it is #4 or larger).
As to leaving it that way "temporarily", I wouldn't have if I was taking ownership of it. I would have locked the circuit out. Just MHO.
jtester
Senior Member
- Location
- Las Cruces N.M.
Actually it was probably much safer before you unbonded the neutral. Many systems operate just as you describe, and the neutral acts as a ground wire as well as a neutral. As Brad pointed out, if these were determined to be separate structures the installation was proper.
In your case, now there is no ground wire, just a driven ground at each pole. It is unlikely that a driven ground rod would operate even a 20 amp breaker in a timely fashion.
Jim T
- Location
- Massachusetts
bdarnell said:
Brad IMO the NEC clearly considers a lighting standard a structure.
The NEC felt a need to place an exception to 225.32 that exempts lighting standards from the disconect means required for separate structures.
Matt your company should immediately place the bond back on the pole. :!:
I agree with Jim T that it is now more dangerous than it was before you lifted the bond.
At this point if there is a line to pole fault the pole will be at line voltage relative to earth and the overcurrent protection will not open.
The ground rod is doing NOTHING the pole already had a concrete encased electrode.
IMO the original design is poor and a EGC should be installed but until that time your company has created an NEC violation and made a bad situation worse.
Bob
bdarnell
Senior Member
- Location
- Indianapolis, IN
- Occupation
- Retired Engineer
iwire said:
Point taken, Bob. I've seen it held both ways. If it's to be considered a structure, then you gentlemen are 100% correct and I emphatically agree. The bond must be replaced.
fc
Senior Member
- Location
- New Jersey
I agree it was a poor design. So if the way it was wired is not in violation you need to find out why people are getting shocked.
I know that the NEC calls a pole a structure only because of the exception 225.32. but I have a real hard time accepting that.
iwire you said "The ground rod is doing NOTHING the pole already had a concrete encased electrode"
How's that a concrete encased electrode?
I know that the NEC calls a pole a structure only because of the exception 225.32. but I have a real hard time accepting that.
iwire you said "The ground rod is doing NOTHING the pole already had a concrete encased electrode"
How's that a concrete encased electrode?
- Location
- Massachusetts
fc said:
The pole base is essentially a concrete encased electrode, the ground rod will not drop the resistance much at all below what the concrete base is already providing.
It does not meet the the NEC as an 'official' CEE.
Regardless there is no grounding electrode available that will make this pole safe with a line to pole fault.
I think MDP has found an NEC violation in 410.15.
- Location
- Massachusetts
As a side note why is it many people resit calling a pole a structure?
The NEC had to call items like sign and light poles we supply power to something other than buildings.
IMO based on the NEC definition of structure anything man made is a structure.
The NEC had to call items like sign and light poles we supply power to something other than buildings.
IMO based on the NEC definition of structure anything man made is a structure.
fc
Senior Member
- Location
- New Jersey
If it is a violation of 410.15.
How could it be considered a structure?
How could it be considered a structure?
fc
Senior Member
- Location
- New Jersey
iwire said:
If that is the case than everything (that we use as in material) is a structure.
- Location
- Massachusetts
fc said:
I don't understand.
Here is how I see it
The pole is a structure and that would mean 250.32(B)(2) could be applied.
However another section 410.15 specifically tells us how we must ground a light pole.
It happens that 410.15 eliminates (or so it seems) the option of 250.32(B)(2)
There is another issue no one has mentioned.
These poles may not be subject to the NEC, if they are installed under the NESC for example they would be fully compliant.
- Location
- Massachusetts
fc said:
Yes everything man made.
Even I will not say a tree is 'built or constructed'. :lol:
But what is wrong with a structure being any man made object we supply power to?
Be it a 60,000 sq ft garage, a small garden shed or just a light pole electricity behaves the same way so why would the rules be different?
fc
Senior Member
- Location
- New Jersey
I think this whole thing with a pole and a GEC when you have more than a multi wire going to it makes no sense. Like you said what is the GEC going to do?
NOTHING.
NOTHING.
eric stromberg
Senior Member
- Location
- Texas
But even if the pole is a 'structure' how does that alleviate the requirements of 250.4(A)(3) and (4)?
Eric
Eric
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
First off, aren't we assuming this sucker is governed by the NEC, and not the NESC? Is there a service supplying this pole, or just a transformer?
I disagree:
It sure would make a purdy candidate for 250.52(A)(2)(4), though, wouldn't it?iwire said:
iwire said:
I disagree:
:lol:
Those sections declare we must bond, but does not tell us a method of bonding. All bonding of services is accomplished through the neutral conductor from the utility. All bonding of detached structures as covered in 250.32(B)(2) is accomplished through the feeder neutral.Eric said:
- Location
- Massachusetts
georgestolz said:
I think I already mentioned that :lol:
georgestolz said:It sure would make a purdy candidate for 250.52(A)(2)(4), though, wouldn't it?iwire said:
:? :?:
georgestolz said:
Not very familiar with that standard but I believe that code would say the tree was created.
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
I would be concerned as to what is causing the difference of potential.
If the grounded conductor has low impedance back to the panel and the panel has low impedance back to the transformer and the grounding at the transformer is in good shape, I would think no one would be getting shocked.
I would take a voltage reading between the pole and the surrounding ground with the circuit energized and again with it de-energized.
Are people getting shocked at every pole?
Please let us know what you find.
If the grounded conductor has low impedance back to the panel and the panel has low impedance back to the transformer and the grounding at the transformer is in good shape, I would think no one would be getting shocked.
I would take a voltage reading between the pole and the surrounding ground with the circuit energized and again with it de-energized.
Are people getting shocked at every pole?
Please let us know what you find.
cwolf
Member
- Location
- Pennsylvania
Let's say the fixture ballast would short to ground( in this case the pole since there is no grounding conductor present) and for some reason the neutral was broken between the source and this pole, anyone coming into contact with this pole would become the path of least resistance to ground. This sounds like an extremely dangerous installation. There is only one solution to this problem, and that is to install a proper equipment grounding conductor to each pole. 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.
jtester
Senior Member
- Location
- Las Cruces N.M.
Unbonding the neutral did the same thing as breaking the neutral in your first scenario. That has created a hazardous situation, the idea that it wasn't code compliant to begin with notwithstanding.
Relying on ground rods will not "lessen the possibility of someone coming in contact with an energized pole". Since no OCPD will trip and since in most cases the ground rod is ineffective in protecting against touch potentials, I believe that the hazard has been increased, not decreased.
Jim T
- Status