Light poles with ground rods

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480sparky said:
There will be those who sue you because you didn't install a ground rod at the light. ("You failed to properly protect the poles with a rod....")

And there are those who will sue you because you did install a ground rod at the light. ("Driving a rod caused the pole to attract lightning.....")
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Those are the 10 kinds of people you have to watch out for.:smile:
 
480sparky said:
....those who understand binary code, and those who don't.....:D
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Actually, there are three types of electrical professionals. Those that can count and those that cannot...
 
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bphgravity said:
Actually, there are three types of electrical professionals. Those that can county and those that cannot...
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Suppose you live in Alaska or Louisiana, where they don't have counties?:D
 
In the case where more than one multi-wire branch circuit is supplied to the

pole ( a seperate structure ) a grounding electrode is required 250.32. So

saying that the NEC does not require a GES at a parking lot pole is not the

whole story.
 
benaround said:
In the case where more than one multi-wire branch circuit is supplied to the

pole ( a seperate structure ) a grounding electrode is required 250.32. So

saying that the NEC does not require a GES at a parking lot pole is not the

whole story.
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Are you permitted to have more than one MWBC to a structure?
 
Installing a ground rod at a metal light pole can provide extra protection from possible electrocution. If the pole was to become energized and not draw enough current to trip an overcurrent device, the ground rod could keep the pole and the earth around the pole at the same potential. If an unexpecting person touched the energized pole, their feet and hands would be at the same potential.

Thoughts?

Jeff
 
jbt260 said:
Installing a ground rod at a metal light pole can provide extra protection from possible electrocution. If the pole was to become energized and not draw enough current to trip an overcurrent device, the ground rod could keep the pole and the earth around the pole at the same potential. If an unexpecting person touched the energized pole, their feet and hands would be at the same potential.

Thoughts?

Jeff
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Take a look at Mike's graphic:

1113844523_2.jpg
 
jbt260 said:
Installing a ground rod at a metal light pole can provide extra protection from possible electrocution. If the pole was to become energized and not draw enough current to trip an overcurrent device, the ground rod could keep the pole and the earth around the pole at the same potential. If an unexpecting person touched the energized pole, their feet and hands would be at the same potential.

Thoughts?

Jeff
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First thought: this is a code violation, second: it is impossible to obtain the same potential therefore dangerous touch voltage will exist!

Fault current is always trying to return to source NOT earth. If you have an ungrounded system (no ground bond at the source) you can have one short and there is no potential (no reference) to earth so there is no shock hazard. If you have a grounded system (bonded at the source) and your trying to use the electrode earth as a fault path you can have an earth path with 7 ohms one minute and 500 ohms the next: 17A at 120V and .24A revealing the 120V WILL REMAIN on the frame of the pole and a 20A circuit will not open from the short!

We never use electrodes this way in premises wiring and it's a code violation to use earth 250-4(A)(5). We only install electrodes to meet the criteria of 250-4(A)(1).
 
tryinghard said:
First thought: this is a code violation, second: it is impossible to obtain the same potential therefore dangerous touch voltage will exist!

We never use electrodes this way in premises wiring and it's a code violation to use earth 250-4(A)(5). We only install electrodes to meet the criteria of 250-4(A)(1).
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I agree with you. The ground rod was not intended to be part of the effective ground fault current path. The intent was to limit the voltage between the metal pole and the surrounding earth.

But, according the the graphic in infinity's post, this would not provide sufficient protection.
 
By the way, the voltages in Mike's graphic come from a table that can be found in the IEEE Green Book.
 
don_resqcapt19 said:
By the way, the voltages in Mike's graphic come from a table that can be found in the IEEE Green Book.
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I was wondering where that information came from. Thanks Don. :smile:
 
I had an "engineer" call me today asking about the 25-ohm resistance for 2 rods installed at a lighting pole. His question was what they should do if two rods did not provide the "required" 25-ohms resistance? I told him to do nothing, once you drove 2 rods you were done, in fact you did not need to drive any rods at a pole. He told me I was wrong, that they were required by the NEC. That without a low resistance path to the earth a circuit breaker would never trip. I referred him to 250.32(A) Exception. He started stammering and said that he was going by "another NFPA document that requires lightning protection at each pole". He was very disappointed that I would not support his completely erroneous conclusions. It is a shame that the term "engineer" can mean anything from a clueless flunky to some of the most brilliant minds in the world...
 
haskindm said:
I had an "engineer" call me today asking about the 25-ohm resistance for 2 rods installed at a lighting pole. His question was what they should do if two rods did not provide the "required" 25-ohms resistance? I told him to do nothing, once you drove 2 rods you were done, in fact you did not need to drive any rods at a pole. He told me I was wrong, that they were required by the NEC. That without a low resistance path to the earth a circuit breaker would never trip. I referred him to 250.32(A) Exception. He started stammering and said that he was going by "another NFPA document that requires lightning protection at each pole". He was very disappointed that I would not support his completely erroneous conclusions. It is a shame that the term "engineer" can mean anything from a clueless flunky to some of the most brilliant minds in the world...
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I agree with your assessment. He seems confused between equipment grounding and lightning protection which are two different animals.
 
I need to apologize to the "engineer" mentioned in my previous post. He called a second time and apparently we had not communicated well during our first conversation. He is seeking information regarding grounding and receiving conflicting information from the "experts". I think I have convinced him that ground rods serve little or no role in clearing faults at line voltages. I commend him for at least searching for answers and sympathize with the misinformation that he is getting. In the event of an open neutral, he was under the impression that a "good" grounding system would clear a fault. I think he now understands that there is no substitute for solid neutral connections and an effective ground fault return path using a grounding conductor. I have enjoyed the exchange and apologize if I came off as arrogant.
 
infinity said:
Are you permitted to have more than one MWBC to a structure?
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I would hope so, 250.32(A)(excp.) seems to back that up. My thought was

if 2 or 3 480vac circuits were run to a pole and then branch off from there to

feed poles on these other circuits ( feed thru ) , then that pole would have

more than one MWBC in it and therefore require a GE ? yes/no.
 
250.32(A), Exception: A grounding electrode shall not be required where only a single branch circuit supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the conductive non?current-carrying parts of equipment. For the purpose of this section, a multiwire branch circuit shall be considered as a single branch circuit.
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I'd say no, the other circuits aren't supplying the structure, they are only junctioned there. ;)
 
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