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Should the ground rod installed for lightning protection measure less than 25 ohms to ground?
[This message has been edited by George Little (edited 04-30-2005).]
George Little
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George
That is a good question.I looked in a few of my resources and did not see any minimum value given as a point of reference.
I did see a minimum of an 8 ft ground rod that shall extend 10 feet vertically in the earth.
Pierre Belarge
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"...an 8 ft ground rod that shall extend 10 feet vertically..."
This I gotta see!
[This message has been edited by Larry Fine (edited 05-01-2005).]
Larry Fine
Fine Electric Co.
fineelectricco.com
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simple, dig a hole 2 ft deep and drive the rod to the bottom, cover with dirt
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Because that lightning protection ground rod gets bonded to the building's grounding electrode system, your results/regulation is by the NEC (more than one rod, no maximum resistance).
NFPA 780 doesn't have a maximum resistance established that I'm aware of.
Ron
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Larry
That is a requirement from NFPA 780-Standard for the Installation of Lightning Protection Systems.
3.13.1 & 3.13.1.1
Ths standard has an illustration that shows an 8' groundrod buried 2' to make up the 10' vertical burial depth.
I have seen this done many times, as it seems the big homes and larger office buildings are all installing lightning protection these days.
Pierre Belarge
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If you do a radio tower you will see guys who are serious about ground electrodes.
I inspected a bunch of Florida DOT "radio equipment shelters" (the little shack under the tower).
They use a Ufer, coupled to ground rods (up to 40') at the corners, a ground ring and buried radials out from there. Everything is cadwelded.
Greg Fretwell
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Greg don't you live in the lightning capitol of the world?
Bob Badger
Construction & Maintenance Electrician
Massachusetts
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Yes, Roxie and PC, I knew that. It just struck me funny the way you (PC) worded it.
About two years ago, we did the ground work for a cellular phone tower. Rods every four feet along the ground ring, which was solid #2 tinned copper, and all spliced exothermically welded; all in a 2'+ ditch.
Larry Fine
Fine Electric Co.
fineelectricco.com
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Insight from another northern guy....what about a 10' x 3/4" rod????
BTW, anoyone ever install Lyncole Grounding devices?? Now that was a 'trip'!
John
John
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