Article 250 Grounding and Bonding: Page 2 of 2

Intermediate

Inside this Article

Grounded (grounding)—Connected (connecting) to ground or to a conductive body that extends the ground connection.

This refers to the physical connection between the earth and the material we are using for the ground reference: the grounding electrode (defined next). The diagram helps illustrate where the grounding connection, as opposed to the bonding connection, happens.

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

The grounding electrode is how our electrical system makes its connection to the earth. Common types of grounding electrodes include ground rods and concrete-encased electrodes, known as an “Ufer grounds.” A ground rod is typically a 5/8-inch-diameter by 8-foot-long copper rod driven into the ground. A Ufer ground uses the rebar installed in a building’s foundation and encased in concrete. Section 250.52 defines other acceptable types of grounding electrodes.

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

This is a term used repeatedly throughout the Code and in our everyday PV language. A common use describes the action we take when establishing a low-resistance connection between the PV modules’ aluminum frame and the support rails. This connection can be made using a variety of methods, but in all cases, the goal is to create a long-term and reliable connection between the metallic components. This connection is made with a bonding conductor or jumper as defined in the Code.

Grounding conductor, equipment (EGC)—The conductive path(s) installed to connect normally noncurrent-carrying metal parts of equipment together and to the system-grounded conductor or to the grounding electrode conductor, or both.

This is the conductive path, in PV systems typically accomplished with a conductor, that makes an electrical bond to all of the metallic components. The Code defines the acceptable EGCs in 250.118. The purpose is to create an effective ground-fault current path, reducing risks associated with faults.

Grounded conductor—A system or circuit conductor that is intentionally grounded.

This is a current-carrying conductor that has an intentional bond to a grounding conductor, establishing a reference to ground. In AC circuits, this is the neutral conductor. The current-carrying conductor-to-ground bond is typically established in one location—the main service panel—with a conductor known as the main bonding jumper. For PV systems, the grounded conductor is most often the negative conductor and the bond between it and the grounding conductor, in batteryless PV systems, is within the inverter, across the ground-fault protection device.

Grounding electrode conductor (GEC)—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 conductor makes the connection from the grounding electrode to the electrical system. In traditional AC systems, the GEC is commonly a copper conductor that originates in the main service panel and is bonded to the grounding electrode. In PV systems with transformer-based inverters, the GEC is required to connect the inverter to a grounding electrode. A variety of methods are allowed for this connection in PV systems; the diagram illustrates just one of those methods.

Because many terms use similar language, yet refer to different portions of the system, it is important to understand the definitions of each. A simple misstatement can lead to confusion or misapplication of the Code.

Access

Ryan Mayfield is the principal at a design, consulting, and educational firm with a focus on PV systems. He is an ISPQ Affiliated Master Trainer and has been accused of talking about bonding and grounding too much in class.

Comments (0)

Advertisement

X
You may login with either your assigned username or your e-mail address.
The password field is case sensitive.
Loading