Ground rod in every light pole?

[hillbilly1]

Yeah, that’s the government for you! Wasting money on rigid conduit for a parking lot! In commercial, unless it was a really weird customer, you would always have the parking lot completely in pvc.

 

[tom baker]

If you are referring to my post, this is for roadway lighting on aertials with speeds >35 mph. FHWA specs require a breakaway design
For the street lighting jobs I designed it was PVC with the last ten feet RMC, stubbed up into a handhole. We had long runs between luminaire poles. Rigid from handhole to inside pole, 1”

 

[hillbilly1]

If you are referring to my post, this is for roadway lighting on aertials with speeds >35 mph. FHWA specs require a breakaway design
For the street lighting jobs I designed it was PVC with the last ten feet RMC, stubbed up into a handhole. We had long runs between luminaire poles. Rigid from handhole to inside pole, 1”

I was referring to @mtnelect attachment, it’s specs was calling for rigid.

 

[tortuga]

The thing the NEC does not cover well with outside branch circuits and feeders is this situation ( similar to one that has recently been litigated) :
A 7500' plus foot lighting branch circuit (1+ mile bike/jogging path), everything is entirely non-metallic, PVC conduit, fiberglass lamp posts etc.
The EGC is insulated. The voltage is single phase 600V L-L (300V to ground).
Now near the end of the path a splice vault fills with water and a tap block has cracked and failed with exposed conductor to water.
There now is a L to ground connection 6500' wire feet from the 60A breaker feeding the circuit.
There are no ground fault relays or protectors just a regular 600V breaker.
Per NEC code there is no connection between the equipment grounding conductor and the earth other than at the service (a 7.2kV primary service
An additional 2500' away).
Is the voltage gradient around the vault dangerous to the public?
If there was a ground rod at the vault tied to the EGC what would it have accomplished?

 

[raberding]

and then there's this one...

 

[raberding]

or maybe 20 feet of #6.

 

[don_resqcapt19]

The thing the NEC does not cover well with outside branch circuits and feeders is this situation ( similar to one that has recently been litigated) :
A 7500' plus foot lighting branch circuit (1+ mile bike/jogging path), everything is entirely non-metallic, PVC conduit, fiberglass lamp posts etc.
The EGC is insulated. The voltage is single phase 600V L-L (300V to ground).
Now near the end of the path a splice vault fills with water and a tap block has cracked and failed with exposed conductor to water.
There now is a L to ground connection 6500' wire feet from the 60A breaker feeding the circuit.
There are no ground fault relays or protectors just a regular 600V breaker.
Per NEC code there is no connection between the equipment grounding conductor and the earth other than at the service (a 7.2kV primary service
An additional 2500' away).
Is the voltage gradient around the vault dangerous to the public?
If there was a ground rod at the vault tied to the EGC what would it have accomplished

There is nothing that prohibits multiple connections between the EGC and the earth. Any time you have a metallic wiring method there will always be multiple connections between the EGC and the earth. In addition, the code, in 250.54, permits multiple additional grounding electrodes to be connected to the EGC.

A ground rod at the vault will not accomplish anything as far as protection from the voltage gradient, unless you are standing pretty much right on the ground rod.

 

[jaggedben]

What I took from tortuga's post is that the NEC falls short in such situations because it doesn't require ground fault protection such as GFCI or some other residual current device. It does speak to the OP, somewhat, in that more grounding does essentially nothing to protect against shock from man made power sources. The rest of this thread is made up of various guessing about what kind of grounding might mitigate lightning damage, which is a basically a totally different subject.

 

[hillbilly1]

I was troubleshooting a pylon sign on a new Home Depot many years back, 480 volts to ground on the hot, 277 volts neutral to ground! Found they had mislabeled the egc in the homerun, and terminated it on a breaker instead of the ground buss. 20 amp breaker never tripped! Ground rod at every pole, about 30 poles including the two steel pylon sign posts buried in probably 10’ of concrete!

 

[Joethemechanic]

I was troubleshooting a pylon sign on a new Home Depot many years back, 480 volts to ground on the hot, 277 volts neutral to ground! Found they had mislabeled the egc in the homerun, and terminated it on a breaker instead of the ground buss. 20 amp breaker never tripped! Ground rod at every pole, about 30 poles including the two steel pylon sign posts buried in probably 10’ of concrete!

Good thing it was paved or there would have been worms everywhere,

 

[hillbilly1]

Good thing it was paved or there would have been worms everywhere,

Every pole was live! Went back about 10 years later to troubleshoot some pole lights that were out, the poles were hot again! Someone disconnected the egc and repurposed it as a 120 volt hot for the tool rental lift chargers. A 480 bolt ballast went to ground, energizing the parking lot again! There was a steel messenger wire they used between the garden center and a pole out front for temporary power during Christmas, the manager came in and saw flames running up and down it! I would have never believed it if she hadn’t took a video of it!

 

[jaggedben]

I was troubleshooting a pylon sign on a new Home Depot many years back, 480 volts to ground on the hot, 277 volts neutral to ground! Found they had mislabeled the egc in the homerun, and terminated it on a breaker instead of the ground buss. 20 amp breaker never tripped! Ground rod at every pole, about 30 poles including the two steel pylon sign posts buried in probably 10’ of concrete!

How do you mislabel a green wire?

 

[ptonsparky]

How do you mislabel a green wire?

It was a #4 black when pulled.

 

[tortuga]

There is nothing that prohibits multiple connections between the EGC and the earth. Any time you have a metallic wiring method there will always be multiple connections between the EGC and the earth. In addition, the code, in 250.54, permits multiple additional grounding electrodes to be connected to the EGC.

Sure right on , I agree it is permitted. You can't rely on an optional connection to clear the fault.
My point is three are scenarios where NEC compliant installations like Hillbilly and I described could have a L-G fault that a breaker can not clear.
You get enough distance from the only required GES and you just have energized dirt with a ground faulted but otherwise fully compliant feeder.

 

[mtnelect]

Sure right on , I agree it is permitted. You can't rely on an optional connection to clear the fault.
My point is three are scenarios where NEC compliant installations like Hillbilly and I described could have a L-G fault that a breaker can not clear.
You get enough distance from the only required GES and you just have energized dirt with a ground faulted but otherwise fully compliant feeder.

You would have thought their monthly utility bill would have tip them off.

 

[jaggedben]

It was a #4 black when pulled.

On a 20A breaker? Okay, maybe.

 

[ptonsparky]

On a 20A breaker? Okay, maybe.

Sure. For VD, and because they were up on the NEC, they increased the EGC!

 

[mtnelect]

Just a side note, when doing maintenance on intersections. Sometimes, you would find the pull boxes filled with dirt to the top, gophers would tunnel into them and leave them full of dirt. Also, ants would love to eat the insulation off.

 

[jaggedben]

Sure. For VD, and because they were up on the NEC, they increased the EGC!

I mean maybe, but what are the chances. Personally I've never seen wire upsized four sizes for VD.

 

[hillbilly1]

I mean maybe, but what are the chances. Personally I've never seen wire upsized four sizes for VD.

Usually the engineers that draw up the prints do. Grocery stores end up having the largest upsize because the lights are 208 instead of 480 like most big box stores. When you have runs that can be 1000’ or more from the panel, voltage drop can be a big issue with 1000 watt Hid fixtures. With the advent of LED, voltage drop is not such a big issue anymore.