I need to install lightning protection on a very large sweetgum in a New Jersey city. It is the largest thing of any kind in the neighborhood. I've got the room and the soil depth to ground it, but the grounding location is perhaps only 20 feet from the nearest house. This house does have lightning protection of its own. It is suggested that I interconnect with this system, but to do so will add a great deal to the cost of the system, since I will have to tunnel under a driveway.

Is this really necessary?

Reply to post by Bill Logan, on January 30, 2003 at 18:03:18:

I do not know if it is apppropriate to connect two grounding systems.

What is required for your Tree Lightning Protection System is adequate grounding for its functioning. That requires a certain conductivity with the earth. That is usually acheived by driving a ground rod to a specified depth. If you can't get that depth you can use multiple shorter rods or if soil is too shallow a plate. You must also adjust for sandy or gravelly soil.

In any case you should install according to the ANSI A300 TLPS Standard. ISA should also be releasing associated Best Management Practices.

The owner should really investgate if their fire insurance will be effected if the systems are or are not joined. If this is an issue the extra cost may be well worth it.

Reply to post by Scott Cullen, on January 30, 2003 at 18:03:18:

Thanks, Scott.
I know the ANSI standard. What is troubling me is something I say in a society of Municipal Arborists posting that said this interconnection was necessary. It made me wonder: what if, I am specifically attracting lightning (by placing the air terminal) to the tallest thing in a neighborhood, which is a tree already disposed to be struck by lightning? What if by doing so, I direct lightning into the power lines or into the house systems, instead of into the ground? I guess I don't know electricity well enough to know if the copper path is strong enough to make it forget about all the other possible paths in the area.

Reply to post by Bill Logan, on January 31, 2003 at 07:16:44:

I don't know either. I would rely on standard rather than what an internet posting says. Maybe you can find out from that poster if there was an authoritative source for the recommendation.