When you are dealing with codes and standards you learn how important it is to choose the proper words. The Code requirements are what products are evaluated against to be “listed for the purpose.” And the Listing standard determines the testing of a product to evaluate its suitability for the installation and use in conformity with the Code (Article 110). Quite often products are specified with a reference to the Listing Standard because the listing is very specific to the tests and procedures used to conduct the product evaluation. The specifier or designer is assured that the product listed to the standard has the properties needed to comply with the Code and installed performance requirements. These standards ensure that products function as intended in the field and properly mate with cable and raceway system components.
An ongoing problem in specifying our products is the use of the term “fitting” in conjunction with the threaded conduit nipples, or threaded or unthreaded factory made elbows and threaded couplings for use with Rigid and Intermediate Metal Conduit or Electrical Metallic Tubing. It is misleading as to what standard they may be listed to and therefore, their suitability for some applications in the Code.
The listing standards applicable to Rigid Metal Conduit (RMC), Intermediate Metal Conduit (IMC) and Electrical Metallic Tubing (EMT) are UL 6, 1242 and 797 respectively. The scopes (Clause 1.1) of these standards include nipples, elbows and couplings with the exception of EMT which only includes elbows. These items are not considered “fittings” except for the integral couplings I will address later.
The listing standard for the “fittings” used with these raceways is the Standard for Conduit, Tubing and Cable Fittings, UL 514B. The reference to fittings within the above mentioned raceway standards is to connectors, couplings, hubs, bushings, etc. that are listed to UL 514B as noted in the standard. These are made from die-cast, iron, malleable iron material or non-metallic materials and are used to provide additional properties required by the system design or simply to join straight sections. A good example would be EMT which has straight section and elbows listed to UL 797 but no component to join them to create a system.In the case of RMC and IMC fittings “listed for the purpose” are need to connect to a box, enclosure or transition to another raceway type or conduit which are not provided for under their listing. Fittings listed under UL 514B are needed.
The three National Electrical Code® (NEC®) Articles that specifically address the requirements, permissions and limitations of our products are 342 Intermediate Metal Conduit, 344 Rigid Metal Conduit and 358 Electrical Metallic Tubing. In Part I. General, of each Article, you have a Scope Section XXX.1, Definition Section XXX.2 and the Listing Requirements Section XXX.6. The XXX is a place holder the applicable Article number. These Articles, of course, can be and often are modified by other sections of the Code.