Severe physical damage

[teed]

My first attempt to use the forum!
For better protection from lightning and high frequency surges, I would like to run a #4 AWG copper grounding electric conductor in the basement of a single family home without using metallic conduit. NEC 2002 Article 250.64 (B) allows this if the conductor is not "exposed to severe physical damage". When referring to #6 AWG copper grounding conductor, the NEC uses "exposed to physical damage". Is there a definition of "exposed to severe physical damage" anywhere?

I know that placing a grounding conductor in a conduit, such as EMT, results in a high impedance for high frequency current. Bonding the conduit and conductor at both ends lowers the impedance, but it is not as good as having no metallic conduit at all.

 

[ryan_618]

Re: Severe physical damage

Hello Teed, and welcome. I think you'll have to ask the AHJ for his/her opinion, as these are not defined terms. In my opinion, it would be difficult to find an area succeptible to severe physical damage anywhere in a dwelling unit.

[ September 15, 2003, 01:11 PM: Message edited by: ryan_618 ]

 

[hornetd]

Re: Severe physical damage

I have used schedule 80 PVC to provide mechanical protection to GECs. I would think that you could take that track.
--
Tom

 

[bob]

Re: Severe physical damage

Teed
In your post you say you want to install #4 copper
as your GEC rather that #6. Do you expect the larger size to be more effective?

 

[teed]

Re: Severe physical damage

Bob,
I need a #4 copper GEC for the new 200 Amp service. I only mentioned the #6 because the NEC mentions a different degree of physical damage. The #4 is sized for 60 Hz. fault current. I would not put in a larger GEC to try to get lower impedance for high frequency surges.

hornetd,
Thanks for the suggestion for using PVC. That would take care of my lightning concern. Some municipalities are afraid that PVC is toxic in a fire, although even burning wood is toxic. I think a #4 GEC could easily be installed without being exposed to severe physical damage.