What do people think about the practice of installing a ground rod at a concrete parking lot light pole base? My take is that the metal pole should be bonded to the building power system, and an additional ground rod in this position is not adding anything. In addition, a concrete pole base, with encased rebar, is inherently grounded and is a lower impedance ground than any ground rod. The pole, being bolted to this base, has a pretty good place for a lightning strike to go (a parking lot pole being a good lightning rod) and the extra ground rod is superfluous. What do people think?
Ground rod at light pole base
- Thread starter lile001
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bkludecke
Senior Member
- Location
- Big Bear Lake, CA
- Occupation
- Retired Electrical Contractor
I think you've got it right.
bphgravity
Senior Member
- Location
- Florida
I doubt it will be possible to NOT make a connection between a supplementary electrode conductor and the EGC to a metallic light pole consdiering both have to terminate on the same object...
That being said, it doesn't really matter as indicated in the OP. TVSS on the remote lighting circuit is your best bet for protection of the premise wiring to lightning surge damage. There is not much hope for a light pole directly struck by lightning - no matter how well it is grounded or how many ways you ground it.
That being said, it doesn't really matter as indicated in the OP. TVSS on the remote lighting circuit is your best bet for protection of the premise wiring to lightning surge damage. There is not much hope for a light pole directly struck by lightning - no matter how well it is grounded or how many ways you ground it.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
A ground rod at a metal pole with a concrete base will not offer any additonal protection from lighting. The concrete and its reinforcing steel are more than adequate. I have a IEEE report from the 1970s that documents that concrete is not damaged by lighting, as the concrete is conductive and the large surface area prevents damage. There is a report by ERICO that states damage form high voltage high current to concrete, but a lighting strike does not behave the same as AC current
Use of a ground rod to protect metal pole bases is myth. If your engineer has documentation, I and Mike Holt would like to see it.
If you would like a copy of the report, PM me with your email.
Tom
International Municipal Signal Association representative to the Illumination Engineering Society, member Illumination Engineering Society Roadway Lighting Committee (we write the standard for street lighting RP-8)
Use of a ground rod to protect metal pole bases is myth. If your engineer has documentation, I and Mike Holt would like to see it.
If you would like a copy of the report, PM me with your email.
Tom
International Municipal Signal Association representative to the Illumination Engineering Society, member Illumination Engineering Society Roadway Lighting Committee (we write the standard for street lighting RP-8)
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
However, the ground rod is important if its a time and materials job. Otherwise there is no reason to have one.
lowryder88h
Senior Member
- Location
- Massachusetts
grd rod
grd rod
They are useless as those things on a bull. In this area after mant tests the best we recorded was 750 ohms. Again they are useless.
grd rod
They are useless as those things on a bull. In this area after mant tests the best we recorded was 750 ohms. Again they are useless.
- Location
- Massachusetts
lowryder88h said:
Very nicely put.
dcspector
Senior Member
- Location
- Burke, Virginia
Tori said:
Tori,
I work in the District. I have read the DCMR (District of Columbia Municipal Regulations) Where did You find that ? Please send me a PM if you can.
Thanks
Greg, I do not know where it is found , I can tell you how we found out about it -
We were doing the job Station Place that sits adjacent to Union Station, big job second to SQ. footage only to the Pentigon
We were under the impression that the electrical permit on the building covered the street lights and when we called for a rough in inspection we were rebuffed on site by about 4 people from the DCMR and found out that the permit DID NOT cover the street lights and we needed to pull one asap-they were not very nice about it -threats to shut down the job- and that the pole base needed a two in. pvc feed and a two in. pvc pipe going straight down through the base into the earth for the ground rod which needed 10 feet into mother earth ie 15 '
So core drillers called and core drill down over a 1" pipe through the base to insert a 2" pipe for the grnd rod-we were good on the feed and base needed to be 2" above finished grade.
Sorry I cannot help you more , I was not one of the foreman on the job, I was just there temporarily to push the manpower and finish some outstanding issues and the pole lights were handed to me
We were doing the job Station Place that sits adjacent to Union Station, big job second to SQ. footage only to the Pentigon
We were under the impression that the electrical permit on the building covered the street lights and when we called for a rough in inspection we were rebuffed on site by about 4 people from the DCMR and found out that the permit DID NOT cover the street lights and we needed to pull one asap-they were not very nice about it -threats to shut down the job- and that the pole base needed a two in. pvc feed and a two in. pvc pipe going straight down through the base into the earth for the ground rod which needed 10 feet into mother earth ie 15 '
So core drillers called and core drill down over a 1" pipe through the base to insert a 2" pipe for the grnd rod-we were good on the feed and base needed to be 2" above finished grade.
Sorry I cannot help you more , I was not one of the foreman on the job, I was just there temporarily to push the manpower and finish some outstanding issues and the pole lights were handed to me
Roger , I stood there and listened to the DCMR, they came while I was working out on the side walk -
Greg, I can contact the pm that was on the job tommorow and find more of the details if he still has files on the job and they havent been archived
Greg, I can contact the pm that was on the job tommorow and find more of the details if he still has files on the job and they havent been archived
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- Location
- Massachusetts
Tori said:
Tori, here at this forum we are sticklers about references.
In my opinion the point of a forum like this is to dispel some of the myths that each of us has heard at one time or the other.
The person speaking may have been talking about job specifications or could just simply been wrong.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Hospital Master Electrician
What's DCMR stand for?
- Location
- Windsor, CO NEC: 2017
- Occupation
- Hospital Master Electrician
C'mon, you don't expect me to sift through a thread to obtain the relevant information, do you?
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Reasons why ground rods are installed at metal lighting poles
1. Civil engineer drives the bus on traffic signal installations much street lighting is part of a traffic signal install
2. Always done it that way
3. Utilites started out as providing lighting (Puget Sound Power and Light)
they use ground rods for HV, used for SL as well
4. The concept that a ground rod will clear a fault.
5. Ohms law does not apply
1. Civil engineer drives the bus on traffic signal installations much street lighting is part of a traffic signal install
2. Always done it that way
3. Utilites started out as providing lighting (Puget Sound Power and Light)
they use ground rods for HV, used for SL as well
4. The concept that a ground rod will clear a fault.
5. Ohms law does not apply
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