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Electrical Power and Grounding

Introduction

Ensuring electrical safety is very important and involves some key steps. One of the first things to do is find reliable sources. However, choosing these sources can sometimes be confusing. Some sources might give advice that seems good but could actually be questionable. One way to handle this is to carefully think about why a specific grounding method is being recommended. For example, the writer remembers seeing a nice picture of daisy-chain bonded connected radio equipment, with the last piece connected to earth ground. Although this setup might seem good, it can cause issues if the first piece in the chain gets a power surge, as the only way to the ground goes through the other pieces before reaching the earth. Unfortunately, his poor grounding advice is picked up an propagated around the Internet.

The National Electric Code (NEC) provides guidelines and standards for electrical installations in the United States. When it comes to electronics grounding, the NEC covers this topic in Article 250. This article defines the requirements for grounding and bonding in electrical systems. It ensures the safety of people and property by establishing electrical continuity and conductivity.

This White Paper discusses major points contained in various publications. Links to the original sources may be found in the Reference Section of this paper.

It is highly emphasized to have a certified electrician handle interface connections between your amateur radio equipment and commercial ground.

This White Paper is to used as a reference. Consult with a certified electrician for your system.

Section 1: Essential Terms

Article 250 is a foundational pillar of NFPA 70®, National Electrical Code® (NEC®), and the tables within Article 250 are critical resources for sizing the wiring for the grounding and bonding of an electrical system. Becoming more familiar with the proper use of these tables can help installers ensure effective grounding and bonding on their projects and, in turn, help ensure the safety of those within the building

Essential NEC used in this paper

  • Ground — The earth.

  • Grounded (Grounding) — Connected (connecting) to groundor to a conductive body that extends the ground connection.

    An example of a conductive body that extends the groundconnection is the first 5 feet of a water pipe entering abuilding. It is permitted to connect at this point eventhough it is not a grounding electrode, as the first 5 feet ofthe pipe is not physically in contact with the earth.

  • Grounded Conductor — A system or circuit conductor that is intentionally grounded.These are often regarded as “neutral” conductors in the trade. Section 200.6 requires these conductors to beidentified as continuous white, continuous gray, or having three continuous white or gray stripes along the conductor’sentire length on other than green insulation. Be mindful that grounded conductors can also be phase conductors in certain applications.

  • Grounding Conductor, Equipment (EGC) — The conductive path(s) that provides a ground-fault current path and connectsnormally non-current-carrying metal parts of equipment together and to the system grounded conductor or to thegrounding electrode conductor, or both.

    These are often called “ground” conductors in the trade. Section 250.119 requires these conductors to be bare, covered, or insulated. Covered or insulated equipment grounding conductors shall have a continuous outer finish that is either green or green with one or more yellow stripes.

  • Grounding Electrode — A conducting object through which a direct connection to the earth is established.

    Section 250.52(A)(1–8) lists the permissible grounding electrode options. While all the available grounding electrodes are required to be bonded per 250.50, it’s fair to say the most common are typically rod and pipe electrodes (i.e., ground rods), which are listed in 250.52(A)(5), and concrete-encased electrodes, which are listed in 250.52(A)(3). Often, concrete-encased electrodes consist of rebar that is embedded in the concrete footings of a building.

  • Grounding Electrode Conductor — A conductor used to connect the system grounded conductor or the equipment to a grounding electrode or to a point on the grounding electrode system. This is the conductor that connects the grounding electrodes to the electrical system. Ground-Fault Current Path — An electrically conductive path from the point of a ground fault on a wiring system through normally non-current-carrying conductors, equipment, or the earth to the electrical supply source.

  • Effective Ground-Fault Current Path — An intentionally constructed, low-impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground-fault detectors. An effectively designed ground-fault current path will allow for circuit breakers, fuses, and ground-fault detectors to open properly when ground-fault conditions arise within the electrical system.

  • Bonded (Bonding) — Connected to establish electrical continuity and conductivity.

  • Bonding Conductor or Jumper — A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected.

  • Bonding Jumper, Equipment — The connection between two or more portions of the equipment grounding conductor.

  • Bonding Jumper, Main — The connection between the grounded circuit conductor and the equipment grounding conductor at the service.

  • Bonding Jumper, System — The connection between the grounded circuit conductor and the supply-side bonding jumper, or the equipment grounding conductor, or both, at a separately derived system.

Section 2: Grounding at the Main Service Entrance

The typical Radio Amateur should not work directly on the Main Service Entrance, It is important to know the basics of how the Main Service Enterance is wired. The Radio Amateur should know how the radio equipment interfaces with the Entrance Circuit Breaker Panel.

It is highly emphasized to have a certified electrician handle these interface connections.

Separate System with more Than One Enclosure
To prevent parallel neutral current paths in raceways and
enclosures, the system bonding jumper can be either be
internal to the panelboards or installed at the separately
derived system enclosure so that it connects any supply-side
bonding jumpers to the system grounded conductor terminal.
The system bonding jumper cannot be installed at both
locations.

Note: Notice that this configuration only uses one ground rod to ensure that both panels are at the same ground potential

Section 3: Grounding in the Ham Shack

Reference Material

NEC/NFPA “GROUNDING AND BONDING
Using the Tables in Articles 250 of the NEC”

“NOT ALL LIGHTING PROTECTION IS CREATED EQUAL”
ELECTRICAL BUSINESS · September 2016 EBMAG.COM

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