Grounding of Luminaires with Exposed Conductive Parts (Section 410.42)

By: Robert Key | Jan 05, 2022

Electrical professionals understand that the purpose of the Code is the practical safeguarding of persons and property from hazards arising from the use of electricity. The average homeowner knows that electricity is dangerous and stays away from bare wires. But does the average homeowner know that their lighting fixture could be energized? Probably not. For example, let’s say an ungrounded conductor escapes the confines of the wire nut and contacts the housing. Suddenly, we have a dangerous situation. This illustrates why the Code differentiates between qualified and unqualified persons, and why there are many places in the Code where accessibility by unqualified persons makes a significant difference.  

As a reminder, let’s review the definition of a “qualified person” from NEC (National Electrical Code) Article 100: 

Qualified Person. One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved.  

Although “unqualified person” is not specifically defined in the Code, it is obvious that someone who lacks this knowledge and skill would be considered an unqualified person.  

Section 410.42, Luminaires with Exposed Conductive Parts, is one example of how the 2020 edition of the Code addresses that difference in a clearer way. This Section has been rewritten to clarify that grounding requirements are different when luminaires that have exposed conductive or metallic parts are accessible to unqualified persons. So how is this condition addressed?  

First, let’s compare the new versus the outdated version of Section 410.42: 

2017 NEC: 

Exposed metal parts shall be connected to an equipment grounding conductor or insulated from the equipment grounding conductor and other conducting surfaces or be inaccessible to unqualified personnel. Lamp tie wires, mounting screws, clips, and decorative bands on glass spaced at least 38 mm (1 1∕2 in.) from lamp terminals shall not be required to be grounded. 

 

2020 NEC: 

Exposed conductive parts that are accessible to unqualified persons shall be connected to an equipment grounding conductor or be separated from all live parts and other conducting surfaces by a listed system of double insulation. A picture containing wall, indoor Description automatically generated

Exposed conductive parts that are accessible to unqualified persons shall be connected to an equipment grounding conductor or be separated from all live parts and other conducting surfaces by a listed system of double insulation (2020 NEC). 

Now, let’s summarize the significant changes to Section 410.42. Section 410.42 has been refined and rewritten for 2020. Most of the language has been revised, resulting in a clearer understanding of how to apply these requirements in a real-world setting. 

  • The entire section comes under the condition accessible to unqualified persons. (It was previously used as an exception to the requirement for connection to an equipment grounding conductor: “or be inaccessible to unqualified personnel.”) The rewritten text clarifies how to apply the requirements in the section. 
  • The new Code language now reads “shall not require connection to an equipment grounding conductor.” This makes it clear that a separate connection to some other grounding means is not required. 
  • Another important change is the requirement addressing exposed conductive parts of a luminaire. This has been strengthened significantly. In the 2020 Code, a listed system of double insulation is required for the luminaire not to be connected to an equipment grounding conductor. In the 2017 Code, the requirement was that the luminaire be insulated from the equipment grounding conductor and other conducting surfaces. 
  • Portable luminaires with polarized attachment plugs are not required to be connected to an equipment grounding conductor. This was not specifically addressed in previous editions of the NEC. This harmonizes with other sections having similar requirements. For example, many of the power tools that we use are double-insulated and do not have a grounding means as part of the attachment plug.  
  • Small isolated parts, such as mounting screws, clips, and decorative bands on glass spaced at least 38 mm (1 1⁄2 in.) from lamp terminals, shall not require connection to an equipment grounding conductor. 

These changes clarify the intent and the conditions of the Code requirement more accurately, leaving less “grey area” for AHJ’s and electrical industry professionals. 

Section 410.42 has been refined and rewritten for 2020. Most of the language has been revised, resulting in a clearer understanding of how to apply these requirements in a real-world setting. 

This is all in harmony with the intent of the Code, which is the practical safeguarding of persons and property from hazards arising from the use of electricity. 

 

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