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#93065 04/30/05 09:33 PM
Joined: Jan 2004
Posts: 1,507
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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#93066 04/30/05 09:48 PM
Joined: Jun 2003
Posts: 681
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
#93067 04/30/05 11:53 PM
Joined: Feb 2005
Posts: 693
" 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.
#93068 05/01/05 05:45 AM
Joined: Apr 2005
Posts: 6
Junior Member
simple, dig a hole 2 ft deep and drive the rod to the bottom, cover with dirt

#93069 05/01/05 08:51 AM
Joined: Mar 2002
Posts: 582
Ron Offline
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.

#93070 05/01/05 08:53 AM
Joined: Jun 2003
Posts: 681
That is a requirement from NFPA 780-Standard for the Installation of Lightning Protection Systems.
3.13.1 &
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
#93071 05/01/05 11:08 AM
Joined: Jul 2004
Posts: 9,881
Likes: 27
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
#93072 05/01/05 11:14 AM
Joined: Jan 2003
Posts: 4,391
Greg don't you live in the lightning capitol of the world?

Bob Badger
Construction & Maintenance Electrician
#93073 05/01/05 04:52 PM
Joined: Feb 2005
Posts: 693
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.
#93074 05/02/05 10:25 AM
Joined: Apr 2002
Posts: 7,374
Likes: 7
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'!


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