Ground rod for signs

R

raberding

Senior Member
Location
Dayton, OH
Occupation
Consulting Engineer
- got a good one coming - Coffee shop with drive-thru.
Inspector wants a stamped letter instructing contractor to install "grounding rods" in each of the Drive Thru Signage Footings. Also wants a sketch of the grounding rod installation method.
I am the EOR. So I asked for a code reference...We'll see what's next...
 
These are separate "structures" from the main building or is there a common overhang/roof covering them? If they're separate, Art 600 (signs) doesn't ask for a GES at the sign although an auxiliary grounding electrode is permitted (but not required).

If they're part of the main building, that GES would cover things.


OTOH, sometimes it's easier to comply than argue, not suggesting this is one of them.
 
these signs are Drive-thru menu board, order board, and directionals (ENTER, EXIT, THANK YOU). Typical fast-food type stuff. All free-standing.
 
raberding said:
these signs are Drive-thru menu board, order board, and directionals (ENTER, EXIT, THANK YOU). Typical fast-food type stuff. All free-standing.
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You did the right thing you've asked for a code reference which doesn't exist. I'm curious to see what they come back with.
 
update - the Site Elec drawings (by the LL's engineer - not me) DO show a ground rod at each light pole base, so the inspector has some "grounds" for requiring those. The sign footings/TI elec sheets (our design) DO NOT show a ground rod.
I think our EC is gonna do what the inspector wants. Just because. Not my reco, but, not my circus.
 
raberding said:
update - the Site Elec drawings (by the LL's engineer - not me) DO show a ground rod at each light pole base, so the inspector has some "grounds" for requiring those. The sign footings/TI elec sheets (our design) DO NOT show a ground rod.
I think our EC is gonna do what the inspector wants. Just because. Not my reco, but, not my circus.
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Some areas they do inspect to the specifications - presumably the plans approved at some point. So anything that is beyond code minimum becomes requirement for that project.

Other places only inspect to code, if designer wants something beyond what code requires then they have to enforce that somehow on their own.
 
raberding said:
update - the Site Elec drawings (by the LL's engineer - not me) DO show a ground rod at each light pole base, so the inspector has some "grounds" for requiring those
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Since it's not required you could just modify the original plan and not install them. Since they're on the original plan then the contractor should have included them in his bid anyway.
 
Pretty cookie cutter on the ground rods at light poles. With all the rebar, and most specs have the pole base 8’ deep, don’t know why they bother with a ground rod, but never had one spec a ground rod at a sign.
 
I recently approached a sign to examine why it was not working and my little pocket voltage wiggy started going off before I even touched anything, I measured about 80 volts from the sign pole to a one of the parking bollards next to it. Not sure if a ground rod would help eliminate the voltage step potential to the bollard but signs and light poles are notorious for that around here.
 
gene6 said:
Not sure if a ground rod would help eliminate the voltage step potential to the bollard
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Just as likely (more likely) the ground rod could be the source. Something goes wrong inside, or was wired incorrectly to begin with, now you have created an electrode. Maybe... who knows...
 
gene6 said:
I recently approached a sign to examine why it was not working and my little pocket voltage wiggy started going off before I even touched anything, I measured about 80 volts from the sign pole to a one of the parking bollards next to it. Not sure if a ground rod would help eliminate the voltage step potential to the bollard but signs and light poles are notorious for that around here.
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Soil conditions make a big difference, I had a call to a brand new Home Depot, pylon sign didn’t work. Checked the voltage to ground, 480 volts. Sign had other issues, because it did have 277 neutral to hot. All of the poles in the parking lot had 480 to ground on two of the three phases. Someone marked the ground wrong, and had it terminated to a 20 amp breaker, even with all of the poles bonded to ground rods, (approximately 30 plus the steel pylon poles) still didn’t trip the breaker.
 
gene6 said:
I recently approached a sign to examine why it was not working and my little pocket voltage wiggy started going off before I even touched anything, I measured about 80 volts from the sign pole to a one of the parking bollards next to it. Not sure if a ground rod would help eliminate the voltage step potential to the bollard but signs and light poles are notorious for that around here.
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Quite possibly no EGC was run to the sign and there's hot-to-ground fault. Mike Holt has done videos about this exact thing, stressing that a ground rod is never a substitute for an EGC, as the code also says.
 
Same here.
gene6 said:
I recently approached a sign to examine why it was not working and my little pocket voltage wiggy started going off before I even touched anything,
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Had a food trailer do that; somewhere up the line the N and G leads had been crossed and, wonder of wonders, they weren't bonded in the trailer. The non-contact stick lite up about a foot from the trailer.
 
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