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BONDING EQUIPMENT TO INTERNAL GROUNDING (EARTHING) SYSTEM CHAPTER 5: INTERNAL GROUNDING (EARTHING)
Utility
Panelboard
Generator
Automatic
Transfer Switch
Telecommunications
cable entry port
Transmission
Line entry port
MGB Grounding
Electrode
Conductor
UPS
Panelboard
Where a RF transmission line SPD is placed at the equipment shelter, equipment room or equipment
area entry point and that entry point is greater than 6.1 linear metres (20 linear feet) away from the
MGB's grounding electrode conductor connection to the grounding electrode system, a grounding
electrode conductor shall properly installed between the SPD and the nearest accessible location of the
common grounding electrode system as covered under NFPA 70-2005, Articles 810.21 and 820.100.
The SPD shall also be effectively bonded back to the MGB by way of its SSGB or a ground bus
conductor.
UPS
Electrical Service
Main Disconnect
Electrical Service
ground
Required #2 AWG Grounding Conductor
for bonding Primary SPD to the MGB.
MGB
IPGB System
Primary SPD for
Telecommunication
cable entry port
Shelter External Ground Ring Conductor
FIGURE 5-32 CABLE ENTRY GREATER THAN 6.1 LINEAR METRES (20 LINEAR FEET) FROM MGB
GROUNDING ELECTRODE SYSTEM.
5.5.1.8.2 PRIMARY SURGE PROTECTION DEVICES
#2 AWG grounding electrode conductor
Required because telecom cable entry port
is located more than 20 linear ft from
MGB grounding electrode conductor
SSGB for
RF SPDs
Alternate Transmission Line entry port
Note: This configuration is to be avoided whenever possible.
Primary SPDs for telephone circuits, data circuits, and control circuits shall have the ground (earth)
terminal bonded to the MGB, SSGB or a dedicated ground bus conductor with an equipment grounding
conductor using bonding methods described within this chapter. The grounding conductor for a single
line primary SPD shall be 6 mm 2 csa (# 10 AWG) or coarser; the grounding conductor for multiple line
primary SPDs shall be 16 mm 2 csa (# 6 AWG) or coarser. Where a primary SPD is placed at an entry
point other than adjacent to the MGB and that point is greater than 6.1 linear metres (20 linear feet)
away from the MGB's grounding electrode, a grounding electrode conductor shall properly installed
between the primary SPD grounding terminal or its SSGB to the nearest accessible location on the
common grounding electrode system as covered under NFPA 70-2005, Articles 800.100, 830.100. See
Figure 5-32 for an example of this type of grounding configuration. In both cases, the conductors should
maintain a minimum 305 mm (1 ft.) separation between cables of different cable groups, even when
conductor is placed in rigid metallic conduit (ANSI-J-STD-607-A-2002).
5-50 68P81089E50-B 9/1/05