User's Manual

Appendix F Grounding Specifications
94 TDC-0971-011 CCU 100 and Repeater 100 Installation Guide
Proprietary and Confidential
A low impedance ground is imperative to both surge protection designs and power
quality. Regularly inspecting and upgrading the system can positively affect the system in
the following ways:
• reduce interference and line noise
• reduce the risk of accidental electrocution
• decrease potentially damaging harmonics
• improve power factors
• improve the efficiency and durability of the surge protection equipment
Understanding Grounding and Bonding
You must have a complete grounding and bonding system between the electrical service
entrance and remotely grounded buildings or equipment. If the remote ground home runs
back to the service entrance, create a single point ground that references the initial utility
company electrical ground back at the service entrance electrical meter.
In this document, the definition of grounding and bonding is as follows:
• Ground/Grounding. Any direct conducting connection between an electrical circuit
or equipment and earth.
• Bond/Bonding. The permanent connection of metallic parts to form an electrically
conductive path. For example, an electrical service panel that is grounded while the
telecommunications rack is bonded to the grounding system.
Understanding the Ohms Level
According to articles 100 and 250 of the NATIONAL ELECTRIC CODE (NEC) an
acceptable ground is rated at 25 Ohms of resistance or less, but optimum performance of
surge protectors is achieved at 5 Ohms or less. Several manufacturers of electronic
equipment also require 5 to 10 Ohms as a maximum resistance for their gear to work
correctly.
Reducing the Ohms level
In many areas of the country you may be starting with 350 Ohms or more. Itron’s
networks are built all over the United States and the geological features can vary greatly
in different parts of the country; therefore, allow the installing contractor to determine
how best to lower resistance to ground (to 5 Ohms or less) in a specific region. The
recommended grounding conductor at the service entrance is specified by NEC based on
the ampacity of the service.
You can perform the following tasks to reduce the Ohms level:
• Measure the resistance to ground at the service entrance meter’s electrical ground,
or of the soil itself. Soil resistance can be affected by the following:
• moisture content
• quality and type of electrolytes
• conductive objects