ERICO Practical Guide to Electrical Grounding - Manual (Page 38)

30 Practical Guide to Electrical Grounding
air without support for more than 3 feet (0.9 m) (Fig. 2-8)
and they must be fastened at a maximum of every 3 feet
(0.9 m) using non-ferrous fasteners. (Fig. 2-9)
Conductor material must comply with the lightning codes
and be compatible with the surfaces which it contacts.
Aluminum conductors cannot be used within 18 inches
(460 mm) of finished grade.
Conductors must be at least the minimum size specified by
the National Fire Protection code (NFPA-780), UL96
and/or LPI-175, and for heavy fault conditions should be
calculated in accordance with IEEE Std 80.
NEC (250-46) requires electrical raceways, equipment, etc.
that are within 6 feet (1.8 m) of a lightning conductor to be
bonded to the conductor at the location where that
separation distance is less than 6 feet (1.8 m). NFPA 780
further clarifies this in cases where a metallic object is
between the downlead and the grounded item. (Fig 2-10) In
addition, Section 250-86 requires that lightning conductors
and driven rods or pipes, or any other made electrode that is
used for lightning system protection shall not be used in
lieu of the grounding electrode system discussed in Chapter
1. This is not to say that the two systems shall not be bonded
together, only that there must be two systems with two
distinct purposes that are interconnected. The intercon-
Fig. 2-8
36"
Maximum
Bridge Over
36"
36" Max
Fig. 2-9
Side Flash Bounding Requirements
Fig. 2-10
Lightning Protection Downlead
Metal Window
Grounded Item
(EG.Water Pipe)
B A
Non-Conductive
Building
If A + B = 6 Feet
Or Less, Bond Lightning
Protection Downlead
To Water Pipe Near Window.
Grounding Book 4/14/99 10/5/99 6:01 PM Page 30 (Black plate)