brookmorris
Member
Gentlemen, 01 Dec 04/0900
Controversy looms again and the ole safety man needs some expert clarification to put the urinary olympia to rest amongst some of the electrical guys versus engineering.
Your help would be greatly appreciated.
Sincerely
Brook Morris
1. Cannot find anything on 'extended down conductor method' (possible Terminology/symantics)in chapter 3 of the 2000 version of NFPA 780 or chapter 4 of the 2004 NFPA 780. I'm not familiar with this method. Can you give me some more specifics?
2. I'm assuming the extended down conductor is to be from the building a minimum of 2ft from the foundation or footer. we are installing masts and overhead wire system, we are assuming this distance for the extended down conductor to be from the lightning mast???
3. If the copper plate option is used (reference 1997 NFPA 780 paragraph 3-13.1.4), when the ground checks are made on the system, where will the disconnect point between the down conductor and copper plate be made? The plates are made with either a connection lug, copper lead wire welded to the plate, or a plate only.
4. If method in question 3 is acceptable should the copper plate be buried at the depth of the rock, or only the minimum (1 to 2 feet in clay soil, or 2 feet in sandy soil)?
5. If the ground resistance check exceeds 25 ohms (US Army Std) for a single copper plate,would it be acceptable to add a second plate 10 feet from first plate and retest?
6. Is there any leeway on the length of ground rod, or is the 10 feet in earth depth the critical element in lightning protection? For example if rock is at 9 feet below existing grade, would an 8 foot rod driven in earth
to a depth of 9 feet, with ground resistance testing at less than 25 ohms be acceptable?
{Moderator's Note: Edited to remove personal contact information. If you wish to contact this person directly, then start by sending a Private Message.}
[ December 01, 2004, 11:11 AM: Message edited by: charlie b ]
Controversy looms again and the ole safety man needs some expert clarification to put the urinary olympia to rest amongst some of the electrical guys versus engineering.
Your help would be greatly appreciated.
Sincerely
Brook Morris
1. Cannot find anything on 'extended down conductor method' (possible Terminology/symantics)in chapter 3 of the 2000 version of NFPA 780 or chapter 4 of the 2004 NFPA 780. I'm not familiar with this method. Can you give me some more specifics?
2. I'm assuming the extended down conductor is to be from the building a minimum of 2ft from the foundation or footer. we are installing masts and overhead wire system, we are assuming this distance for the extended down conductor to be from the lightning mast???
3. If the copper plate option is used (reference 1997 NFPA 780 paragraph 3-13.1.4), when the ground checks are made on the system, where will the disconnect point between the down conductor and copper plate be made? The plates are made with either a connection lug, copper lead wire welded to the plate, or a plate only.
4. If method in question 3 is acceptable should the copper plate be buried at the depth of the rock, or only the minimum (1 to 2 feet in clay soil, or 2 feet in sandy soil)?
5. If the ground resistance check exceeds 25 ohms (US Army Std) for a single copper plate,would it be acceptable to add a second plate 10 feet from first plate and retest?
6. Is there any leeway on the length of ground rod, or is the 10 feet in earth depth the critical element in lightning protection? For example if rock is at 9 feet below existing grade, would an 8 foot rod driven in earth
to a depth of 9 feet, with ground resistance testing at less than 25 ohms be acceptable?
{Moderator's Note: Edited to remove personal contact information. If you wish to contact this person directly, then start by sending a Private Message.}
[ December 01, 2004, 11:11 AM: Message edited by: charlie b ]
