Re: Ul rating of wire nuts
This is from the above mentioned Mike Holt newsletter - this is the UL response regarding 'green' wirenuts being required.
Anwer 2: UL Response
Mike ? I?d like to respond to your inquiry to UL regarding the use of twist-on type wire connectors for connecting equipment grounding conductors. I believe that to properly answer this inquiry we need to reference requirements in both the NEC and the guide information which UL provides for listed products.
Sec. 250-8 of the NEC indicates that grounding conductors shall be connected by exothermic welding, listed pressure connectors, listed clamps, or other listed means. Pressure wire connectors are listed under the category of Wire Connectors and Soldering Lugs (UL Guide ZMVV). A ?twist-on? connector is a type of pressure cable connector that is tested to the UL Standard for Splicing Wire Connectors, UL486C. The requirements for these connectors include mechanical securement tests, as well as their ability to carry continuous current within acceptable temperature limits. Listed products in this category are identified by the words ?Wire Connector? (or abbreviation there of) near the UL Listing Mark which may be on the product or smallest unit container. Based on this information, a listed ?Wire Connector,? including the twist-on type, should be suitable for connecting equipment grounding conductors. There was also some question regarding the color of the connector insulation. Listed insulated twist-on type wire connectors are typically provided in a variety of insulation colors, however, to the best of our knowledge we have not listed a wire connector with green color insulation.
NEC Sec. 250-119 requires covered or insulated equipment grounding conductors to have a green or green with yellow stripes outer finish, but there is no NEC requirement for the color of the insulation of a wire connector used to connect equipment grounding conductors.
NEC Sec. 250-8 also permits ?other listed means? for connecting grounding conductors. UL has a category for Grounding and Bonding Equipment (UL Guide KDER). Grounding Connectors are a special type of connector that is tested to the UL467 Standard for Grounding and Bonding Equipment. The requirements for grounding connectors include mechanical securement tests, but unlike wire connectors, these connectors are not subjected to a continuous current test. In lieu of this test, there is a special short time current test in UL467 to show the ability of a grounding connector to safely conduct fault current. There are some listed twist-on type connectors with green color insulation that are listed as grounding connectors. Listed products in this category are identified by the words ?Grounding Connector? (or abbreviation there of) near the UL Listing Mark which may be on the product or smallest unit container.
It should be noted that grounding connectors are only used for connecting grounding conductors, and unlike listed wire connectors, cannot be used to connect current carrying conductors (including grounded and ungrounded conductors). There are some listed Wire Connectors of the twist-on type that are also tested and complementary listed as Grounding Connectors, and the listing mark information for these products will identify them as both. The insulation on these connectors (with both listings) can be various colors, except green. We understand that some jurisdictional authorities may require listed grounding connectors for connecting equipment grounding conductors, and some may require only those with green insulation, and this is certainly permitted by Sec. 90-4 of the NEC. To satisfy this need, the listing categories of ?Grounding Connectors?, and ?Wire Connectors complementary listed as Grounding Connectors? were established for the manufacturers of these products.
I apologize for this somewhat lengthy explanation, but I believe this detailed information is helpful to those who are interested in understanding the rationale behind product requirements and listings of this type. We at UL are always interested in ways to improve our service to the electrical community, and if you or your readers have any suggestions in this regard, please let us know.
Regards, David Dini, P.E. Sr. Research Engineer Underwriters Laboratories Inc. Northbrook, Illinois Phone: 847 664-2982 Fax: 847 509-6285 Email:
David.A.Dini@us.ul.com </ym/Compose?To=David.A.Dini@us.ul.com&YY=9037&order=down&sort=date&pos=0>
Mike Holt's Comment: Thank you Dave for taking the time to resolve this issue.