Many of the articles that I write for this magazine originate as questions that I receive as I travel, by phone, or come to me as emails. I can answer some of these questions very easily without much controversy by a simple reference to the National Electrical Code (NEC). Some questions take more time and involve a search through my library in which I have proposals, comments, preprints, and other historical background to the 1943 era. I also have the NEC handbooks back to 1913 and the regular NEC to about 1920, but very few questions have answers that date back to that era.
This past week, I received an email question where the origin of the NEC material requiring an equipment grounding conductor and a grounding-type receptacle was from the 1956–1962 era of the NEC, but the answer involved installations in 2013. Prior to the 1956 NEC, receptacles were 2 wire (an ungrounded or “hot” conductor and a grounded or “neutral” conductor) without equipment grounding conductor connection, thus requiring no ground pin on the cord cap.
The question involved cord-and-plug-connected equipment where the manufacturer of the electrical equipment stated in the installation instructions that it must be connected through a grounding-type receptacle. The problem for the installation—raised by the electrical inspector—was that all of the receptacles at the particular site were ungrounded and had been installed in accordance with the NEC at the time of installation, (in other words, prior to the 1956 NEC). The electrical contractor removed the old ungrounded receptacle and replaced it with a ground-fault circuit interrupter (GFCI) receptacle in accordance with 406.4(D)(2)(b) in the 2011 NEC. The inspector recognized the replacement of the ungrounded receptacle with a GFCI receptacle as NEC-compliant but stated the installation instructions required connection to a grounding-type receptacle and cited noncompliance with 110.3(B), since installation instructions must be followed as part of the listing of the electrical equipment. Section 110.3(B) states, “listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.”
Section 2559 in Article 250 of the 1956 NEC, “Portable Equipment,” stated: “non-current-carrying metal parts of portable equipment may be grounded in one of the following ways: (a) By means of the metal enclosure of the conductors feeding such equipment, provided an approved plug is used, one fixed contacting member for the purpose of grounding the metal enclosure, and provided, further, that the metal enclosure is attached to the plug and to the equipment by connectors approved for the purpose; (b) By means of a grounding conductor run with the circuit conductors in cable assemblies or flexible cords, provided an approved plug is used, one fixed contacting member for the purpose of connecting such grounding conductor to the grounded metal raceway or cable armor, or to a grounding conductor installed only for grounding purposes; the grounding conductor in a cable assembly may be uninsulated; but if an individual covering is provided for such conductors it shall be finished to show a green color.” As you can see, the text in the 1956 NEC was similar to what appears in the 2011 NEC in 250.114 and in 406.4.
Some of the changes that occurred between the 1956 NEC and the 2011 NEC involve installations where ungrounded receptacles can be replaced with grounding-type receptacles as permitted by 406.4(D)(1) by simply installing an equipment bonding conductor from the receptacle to the receptacle enclosure where a grounding means exists with the receptacle enclosure or a new equipment grounding conductor is installed in accordance with 250.130(C). A nongrounding-type receptacle is permitted to be replaced with a GFCI receptacle but must be marked “No Equipment Ground.” In addition, an equipment grounding conductor must not be connected from the GFCI receptacle to any outlet downstream of the GFCI receptacle. The electrical contractor installing the equipment complied with all of the appropriate requirements in 406.4(D)(1)(b). The installation was in compliance with the NEC except for the question involving the requirement in 110.3(B).
You should seek a more thorough understanding of the manufacturer’s reasoning for the statement of grounding. If the only purpose of the statement is to provide safety for anyone touching the equipment where it may become inadvertently energized, the GFCI receptacle with its 4- to 6-milliamp or larger trip level will provide personnel protection. If the manufacturer is using the equipment grounding conductor for internal connections for equipment operation function, the installation provided by the electrical equipment would not be acceptable. Asking the manufacturer those questions would be next in establishing compliance for this unique situation.