MESH METHOD & LIGHTNING ARRESTER COMBINATION

jokoMalong

Member
Location
Manila Philippines
Occupation
Electrical Engineer
Hello everyone, I just want to know if a Lightning Arrester (Strike Terminal) need to be interconnected in Mesh Method Lightning protection if I used both in a Lightning protection System of a building. Thank you in advance for your inputs. Have a good day everyone 1596068217974.png
 

jokoMalong

Member
Location
Manila Philippines
Occupation
Electrical Engineer
Since that is covered by a different set of codes from the NEC, you may or may not find someone here to answer that.
I see, Sir what about this . What is the purpose of the 2ft. minimum distance of ground rod to foundation wall? i have a situation below and I don't know what to consider when measuring the 2ft. distance. Is it from the foundation or from the footing. kindly see below image for your reference. hope you can help me out Sir. thank you.
1596088945539.png
 
Last edited:

GoldDigger

Moderator
Staff member
It seems to me that the purpose is probably to minimize the impedance of the ground rod to earth by allowing the near field current around the rod to flow freely on all sides of the rod. In the worst case if the wall/footing were an insulator the impedance of a rod right next to the wall would be twice that of a rod infinitely far from the wall.
Given that motivation, the principle effect is the distance to the obstruction of current along the depth of the rod, but a horizontal barrier underneath the end of the rod could have an effect too. In the end that does not inform us as to what the job specification asks for.
Sorry I cannot help you further.
 

steve66

Senior Member
Like Golddigger said, we cant do much more than guess what the designer had in mind, but keeping a ground rod a couple of feet away from the foundation might also help keep it out from under the roof overhang, where the ground is more likely to get a little more moisture from the rain.

Or maybe they are just trying to help you avoid hitting the footing when you drive the rod.
 

junkhound

Senior Member
Location
Renton, WA
Best if you could tie into the ground rods in the concrete, called a 'concrete encased electrode', much better ground than a ground rod.

Aka 'Ufer ground', after, Herb Ufer, a WW2 UL engineer who did grounding studies and inventions.

No idea why the separation ?
 

Julius Right

Senior Member
If there is a water penetration sealing layer you cannot finish the Ufer grounding-no direct contact with the soil. Some preparation also has to be done prior to concrete pouring.

The lightning stroke current induces in vicinity metallic object voltage differences which in turn may damage the concrete. The magnetic field produced decreases with the distance.

Above the ground line the ground bonding wires reduces the voltage differences but underground we don't have this.
 
Top