On 5/12/11 8:47 AM, bob finger wrote:
> And what NEC code are you reading that allows stranded copper for grounds?
NFPA 780 for lightning allows stranded.
So does NEC, if the bonding conductor is of sufficient size. (note that
Art 820 (cable TV) Antenna "grounding" is AWG14 or bigger, but Art 250
"bonding" of grounds is AWG6 or bigger)
Bonding conductors have to be big enough to carry the maximum likely
fault current (for instance, if you have a green wire ground to a stove
outlet wired for 40A, the bonding wire has to be at least as big as the
wires supplying the power, probably AWG 10 in this case)
There is a recommendation (copied here from one of many FAQs) that
stranded wire not be used, particularly in smaller sizes:
"While NEC Article 820.100 (A)(2) permits the use of solid or stranded
grounding conductors, field experience has shown that stranded
conductors of the sizes normally used in coaxial cable grounding cannot
be securely gripped by clamps commonly used for grounding. The tendency
of the stranded conductor to fray or loosen in the clamp can prevent
achieving and maintaining a secure mechanical and electrical connection.
Therefore, the use of stranded grounding conductors sized No. 6 AWG or
smaller is not recommended."
Also, be aware that when talking about "code", there's THREE different
parts of Art 800 (communications systems) that you might fall under.
800 is telephone, 810 is radio/TV (including amateur), 820 is cable TV,
(and 830 is network powered broadband.. I suppose a FiOS or Uverse would
fit here)
They all have different grounding/bonding requirements. For instance,
810 requires AWG10 for the conductor going from coax shield to ground,
but requires AWG6 for bonding two ground systems together.
Art 820 (CATV) calls for AWG 14 or bigger *insulated* from the lead in
grounding block where the service drop is to the acceptable earth ground.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|