Camera POE - no 120Vac - mounted on concrete pole

Natfuelbilll

Senior Member
Installing a "power over ethernet" POE camera on a concrete pole that are built with a #4 bare ground. Not sure what to do with ground. Anything? There is a steel frame building 100' away. Code or recommendation references gladly accepted.
 

Natfuelbilll

Senior Member
The camera is supplied with POE which is sourced at a nearby building. Just the camera is on the concrete pole. My question is what to do with the ground wire that comes with the pole.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
The camera is supplied with POE which is sourced at a nearby building. Just the camera is on the concrete pole. My question is what to do with the ground wire that comes with the pole.

Nothing. And what does the ground wire connect to with a concrete pole anyway? I assume the reinforcing to keep the wet concrete from being energized when used for a light pole?

-Hal
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Interesting.

250.32 Buildings or Structures Supplied by a Feeder(s) or
Branch Circuit(s).
(A) Grounding Electrode. Building(s) or structure(s)
supplied by feeder(s) or branch circuit(s) shall have a grounding
electrode or grounding electrode system installed in
accordance with Part III of Article 250. The grounding electrode
conductor(s) shall be connected in accordance with
250.32(B) or (C). Where there is no existing grounding electrode,
the grounding electrode(s) required in 250.50 shall be
installed.
Exception: A grounding electrode shall not be required where only a
single branch circuit, including a multiwire branch circuit, supplies the
building or structure and the branch circuit includes an equipment
grounding conductor for grounding the normally non–current-carrying
metal parts of equipment.

I don't believe POE is a branch circuit or a feeder.
 

rnatalie

Senior Member
Location
Catawba, NC
Occupation
Retired Electrical Engineer
By the way, there are several flavors of POE. If this is a pan/tilt camera, it may require the 4PPOE (they parallel the power over all four pairs) to get sufficient ampacity.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
The RGS will act as an equipment grounding conductor. This EGC is not required since you don't have a branch circuit or feeder, but it is there.

I would use a bonding bushing to connect the #4 to the RGS.

My reasoning is that pole and its mounting will act as an earth electrode, and the RGS will either act as an earth electrode or will be connected to the building grounding electrode system. If the pole is not bonded to the RGS then you would likely have all the issues of having _separate_ grounding electrode systems in close proximity, for example concentrating 'stray voltage' from outside sources, or carrying soil currents from nearby lightning ground strikes in through one electrode and out through the other.

You already have the #4 wire, you are already installing the RGS, and a bonding bushing is cheap. I don't believe it would be required by code, but would be a cheap design decision.

-Jon
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
I can offer that the POE cable is being installed in RGS conduit running from the POE injector to the pole.

You already have the #4 wire, you are already installing the RGS, and a bonding bushing is cheap. I don't believe it would be required by code, but would be a cheap design decision.

In that case I agree. Good idea.

-Hal
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
The RGS will act as an equipment grounding conductor. This EGC is not required since you don't have a branch circuit or feeder, but it is there.

I would use a bonding bushing to connect the #4 to the RGS.

My reasoning is that pole and its mounting will act as an earth electrode, and the RGS will either act as an earth electrode or will be connected to the building grounding electrode system. If the pole is not bonded to the RGS then you would likely have all the issues of having _separate_ grounding electrode systems in close proximity, for example concentrating 'stray voltage' from outside sources, or carrying soil currents from nearby lightning ground strikes in through one electrode and out through the other.

You already have the #4 wire, you are already installing the RGS, and a bonding bushing is cheap. I don't believe it would be required by code, but would be a cheap design decision.

-Jon
I doubt it will hurt to do so, and it might make some feel better not to have the #4 wire just hanging.

I do not buy into any of the presumed bad things that might happen. For instance, I see no way for lightning current to flow from the #4 wire to the RGS UNLESS they are connected together.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
I doubt it will hurt to do so, and it might make some feel better not to have the #4 wire just hanging.

I do not buy into any of the presumed bad things that might happen. For instance, I see no way for lightning current to flow from the #4 wire to the RGS UNLESS they are connected together.

I have personally encountered a phone line that appeared to have been destroyed by having two separate grounding electrodes.

The phone line entered the building via a telco block with a wire to a random ground rod.

The electrical system was properly grounded via ground rods on the other side of the building.

The phone was not working.

Upon investigation a random stretch of wire near the floor well inside the building was surrounded by a series of scorch marks along the wall, with the copper conductor broken up and coming out as spikes along the wire at each scorch mark.

There was no evidence of a lightning strike on the building.

The building was located 'near' a set of high voltage transmission lines.

My _guess_ is that a nearby strike caused a difference of potential between the two ground electrodes.

The whole point is that if current is trying to flow between two ground electrodes, you _want_ it to flow through a made conductor, rather than creating a significant potential difference.

-Jon
 
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