250.32

[charlie b]

A new outdoor skateboard park will be lit by pole-mounted lights. I will mount a new 100 amp MCB panel on one of the poles. I will tap an existing transformer (300 KVA, 120/208V) and run an underground feeder to the panel. As I read the code, I will need a grounding electrode at the pole to which the panel is mounted, but not at any other light pole. That is because the first "structure" is served by a feeder, but each of the other lights will only be served by a single MWBC. Is that right? If so, can I use some aspect of the pole itself (presuming it is metal and is imbedded in a concrete base) as the grounding electrode, or will I need to install a pair of ground rods?

 

[iwire]

I think you are correct but I think you are stuck with installing an electrode(s).

 

[Dennis Alwon]

I agree with Bob as I don't think a pole concrete u bolts would qualify as an electrode unless it meets the requirements of 250.52(A)(2)-- It is a bit different in 2011.

 

[stew]

just did a skate park at the Muckelshoot Rec area and the metal lite pole system had installation instructions that called for ground rods at each pole . 10 footers no less and with I think #4 cu. This was an installation specification so of course we did it per the instructions.These were complete pole lite assemblies from Musco. very nice to install as well.One of the most installer freindly systems around and very well engineered right down to the laser aiming system already a part of the light head.

 

[Dennis Alwon]

just did a skate park at the Muckelshoot Rec area and the metal lite pole system had installation instructions that called for ground rods at each pole . 10 footers no less and with I think #4 cu. This was an installation specification so of course we did it per the instructions.These were complete pole lite assemblies from Musco. very nice to install as well.One of the most installer freindly systems around and very well engineered right down to the laser aiming system already a part of the light head.

So what did you hook the ground rods to? A #4 to the egc for the MWBC????

 

[stew]

by the way alwons avatars are cool!

 

[david luchini]

by the way alwons avatars are cool!

I agree with stew

(Sorry, couldn't resist.)

 

[squaredan]

is That is because the first "structure" is served by a feeder, but each of the other lights will only be served by a single MWBC. Is that right?

I was reading 250.32 and saw 250.32(A) Exception,take a look at that, hope that helps sum.. I was also taught that putting a ground rod at lighting poles is absolutly useless...
Dan

 

[charlie b]

Thanks, everyone. I am on the "ground rods at light poles are useless" side of the fence. However, I can?t get around the poles qualifying as ?structures,? and so therefore I need one electrode at the pole that will support the panel. The client is making noises about having receptacle outlets (WP, GFCI) attached to at least some of the poles. That means I need to serve both 208V lights and 120V receptacles. I can manipulate the circuiting so as to use MWBCs, in order to take advantage of the exception, and thereby to avoid the requirement of installing ground rods at each pole.

 

[charlie b]

. . . installation instructions . . . called for ground rods at each pole . 10 footers no less. . . .

Just out of curiosity, how did 250.56 impact this installation? Was there any discussion of putting a second ground rod six feet away from each light pole, or was the ground resistance measured and verified to be under 25 ohms?

 

[Dennis Alwon]

Just out of curiosity, how did 250.56 impact this installation? Was there any discussion of putting a second ground rod six feet away from each light pole, or was the ground resistance measured and verified to be under 25 ohms?

If the instruction for the light call for a ground rod I suspect one is only needed since the NEC wouldn't require any with no panel.

 

[iwire]

I would call it an 'auxiliary electrode' and it would not have to meet 250.56.