Installation Guide

(Megger) is preferred in installations of new equipment that cannot be connected to an existing
ground ring.
The earth resistance meter is less expensive, but it requires multiple ground probes and leads
from the tester with specific distance requirements between rods. Then measurements are
plotted on a monograph in order to calculate the actual resistance of the ground.
Meggers come in three and four terminal configurations. To test the actual resistivity of the soil
itself, use a four terminal model. The advantage of this method is that you are not connected to
the electrical system during testing. An electrical line fault during testing can send high current to
the grounding system, resulting in high current and voltage at the test leads and meter.
Warning! Be safe when working on live electrical systems. Always use proper
protection equipment. If you are in contact with the grounding system (particularly if
the ground rod is disconnected) you are the ground for the system.
Adjusting the Routing of the Grounding Conductor
If more than one ground can be referenced (such as in a campus environment), adjust the
routing of the grounding conductor. This is very important in the system’s ability to reference the
original equipment ground back at the service entrance utility service meter.
The normal routing procedure is to bring the HOT, the NEUTRAL, and the GROUND wire into
the remote electrical panel and terminate them to the appropriate busses. Then route the
GROUND wire down to the house grounding electrode (ground rod).
In this procedure, route the GROUND wire to the grounding electrode first, and then route up to
the ground bus within the panel. This simple adjustment still follows NEC code, but provides an
unobstructed pathway to divert surges to these ground rods while continuing to reference the
service entrance ground. The fundamental result of this routing procedure is the elimination of
potential equipment damage from the ground loop created by multiple ground rods. This method
of routing allows the electrical potential of the entire facility to rise and fall in a uniform manner,
reducing the possibility of excessive current flow on the grounding system.
Finally, inspect and tighten all wiring terminations at the service entrance and at each of the
remote panels, disconnects, or equipment.
Note: To lower resistance to grounding, keep all connections tight and free of oxidation.
The following illustration shows a sample grounding layout.
23 June 2020 TDC-0971-012 Itron, Inc. Page 107 of 134
CCU 100 and Repeater 100 Installation Guide F Grounding Specifications