Welcome back to the series on understanding Article 250, “Grounding and Bonding,” in NFPA 70: National Electrical Code. The previous article discussed the purpose of the equipment grounding conductor (EGC) and how this is accomplished. We also looked at what can be used as an EGC, which is often the star of the effective ground-fault current path. Now it is time to understand what must be connected to this path and how we can identify it in a wiring system.

First, let’s start with an in-depth look at what types of items must be connected to the EGC. We found ourselves in Part VI of Article 250 when we discussed different items allowed to serve as the EGC, and we can start where we left off. 

Section 250.110 gives us a generalized look at conditions that require connecting normally non-current-carrying conductive materials of fastened-in-place or fixed equipment to the EGC. This section applies to metal parts of fixed equipment likely to become energized.

The first conditions

The first condition that mandates connection to the EGC is that the equipment is fastened in place so it is within 8 feet vertically or 5 feet horizontally of ground or a grounded object and subject to contact by a person. This illustrates the safety aspect of the EGC for personnel. If a fault would energize metal parts and a person could come in contact with the equipment, we want the EGC to enable the opening of the overcurrent protective devices to de-energize the circuit before someone gets hurt, or worse.

Connection to the EGC is also needed if the equipment is in a wet or damp location or if it is in contact with metal—again, this is a condition where the electricity can reach someone not touching the equipment. The equipment must be able to be shut down when a fault occurs to prevent serious injury.

The last three conditions

The last three conditions that call for fixed equipment being connected to the EGC are based on the installation. If the installation is in a hazardous location, an unchecked fault in electrical equipment could lead to ignition of the hazardous environment. 

Another installation condition is that if the wiring method supplying the equipment provides an EGC, the equipment must be connected to the EGC provided. 

The last condition is if any terminal of the equipment is connected to a conductor with a voltage above 150V to ground. This has a few exceptions, but it is typical of most NEC sections, which are general in nature. Much of the NEC is made of general rules followed by exceptions for specific conditions.

The EGC can be insulated, covered or bare. If the EGC is a bare conductor,the identification is handled by the fact it is the only bare conductor. For covered and insulated EGCs, however, the general rule is that the conductor must have a continuous outer finish that is either green or green with one or more yellow stripes.

Equipment types

Article 250 also specifies equipment that must be connected to the EGC, regardless of whether it falls under the conditions of the previous section. Many types of equipment are listed here—the list goes from 250.112(A) to 250.112(M)! Many of these items are equipment that will be accessible to a person, are typically in the vicinity of grounded surfaces or are involved with water in some fashion.

A couple of the items do have to meet specific conditions, however, such as 250.112(F) and (I). Section 250.112(F) covers equipment in commercial garages, theaters and motion picture studios but exempts pendant lampholders supplied by less than 150V to ground. Typically, these lampholders only have two wires and are unable to connect to an EGC anyway. Section 250.112(I) deals with remote-control signaling and fire alarm circuits, and exempts Class 1 circuits less than 50V and other types of these circuits if they are not required to be grounded in another part of Article 250.

Finally, there is a section that covers cord-and-plug-connected equipment and nonelectrical equipment. This boils down to anything over 150V to ground and any equipment that is motor-operated or has some sort of hermetic motor-compressor unit. Some equipment also requires an EGC connection if it is likely to be in a person’s hands when plugged in.

Examples include portable handlamps, or a cord-and-plug-connected appliance used in a damp or wet location or an area where the person might be standing in water or on a grounded surface. There is, however, a major exception for cord-and-plug-connected equipment if it uses a system of double-insulation or its equivalent. You’ll know if the double-insulation exception applies because the equipment is required to be marked as such.

You may ask yourself …

When it comes to whether something needs to be connected to the EGC, it comes down to a couple of questions:

• Is an EGC provided in the circuit?
• Is there a conductive surface accessible to a person?
• Is there a return path for current to go back to the source?
• Is the metal surface likely to become energized? (See Article 100 for the definition.)

If the answer to most or all these questions is a “yes,” then it is going to have to be connected to the EGC.

EGC identification

Finally, let’s talk about how the EGC must be identified. Since we already covered the types of items that qualify to be used as an EGC, there is no need to rehash that entire list. Most of the items that qualify have no need to be identified, such as a metallic raceway or metal cable jacket. However, if the EGC is a wire type, there must be a way to differentiate the EGC from the other conductors in the circuit. Section 250.119 has us covered on making this distinction. But, in typical NEC fashion, there are several ways to identify a wire-type EGC.

This section allows the EGC to be insulated, covered or bare. If the EGC is a bare conductor, the identification is handled by the fact it is the only bare conductor. For covered and insulated EGCs, however, the general rule is that the conductor must have a continuous outer finish that is either green or green with one or more yellow stripes. 

Another choice would be to use a nongreen conductor and re-identify it as an EGC. However, this is only allowed for wire 4 AWG and larger or in multiconductor cables, and there are stipulations. The wire must be re-identified at each end and at any accessible point in between, and the wire must be identified as an EGC by one of three methods:

• Stripping the wire bare on any exposed lengths.
• Coloring any exposed insulation or covering green.
• Marking the insulation or covering with green tape or green adhesive labels.

When it comes to the EGC, we have now discussed the purpose of this critical grounding and bonding component, examined what we can use to create this EGC path, what must be connected to it and how to identify the EGC from other conductors in the system. 

The next topic to tackle is how to ensure that the EGC can perform its intended function. Next month’s article will dive into determining the size of the EGC and specific installation rules to protect it. 

Until next time, stay safe and remember to always test before you touch!