Are There Any Acorn Clamps Listed for Rebar?


Are there any UL Listed direct burial brass acorn clamps for use with rebar on a UFER ground? Will there be a galvanic issue with the dissimilar metals?


Yes, UL has Certified (Listed) acorn-type grounding clamps for use on rebar to connect the grounding electrode conductor between steel rebar and the bronze clamp.

Grounding clamps are investigated for compliance with the ANSI/UL 467, the Standard for Safety for Grounding and Bonding Equipment. To reduce electrolytic action between dissimilar metals, UL 467 requires that metal parts in a bonding or grounding path be galvanically compatible. When determining this, UL evaluates all possible combinations of the grounding and bonding device along with its rated electrodes, etc. A suitable plating or coating process delivers the required corrosion resistance.

The guide information details how to identify clamps Certified (Listed) for use on rebar. It states: “Ground clamps intended for use with rebar are marked with the size of rebar with which the clamp is intended. Rebar sizes may be specified in fractions, such as 1/2, 5/8, etc., or a number, such as 3, 4, 5, etc., where the number represents the numerator of the fraction when stated in eighth-inch increments, e.g., 4 = 4/8.” Regarding direct burial identification, it states: “Ground clamps and other connectors suitable for use where buried in earth or embedded in concrete are marked for such use. The marking may be abbreviated ‘DB’ (for ‘Direct Burial’).”

These types of grounding clamps are Certified (Listed) under the product category Grounding and Bonding Equipment (KDER). The UL guide information and certifications can be viewed on UL Product Spec at; enter KDER at the category code search.



Sections 314.27(E) and 422.18(2) of the 2017 NEC were revised to include a new type of receptacle that provides a Listed locking support and mounting receptacle for use with a compatible factory installed attachment fitting that appears to be a quick release system. Are these quick release receptacles and fittings Listed so they can be used to power any type of luminaire or fan?


No. The male attachment fitting is not Certified (Listed) as a stand-alone device for field installation on any product. While the female receptacle is Certified (Listed), the mating male attachment fitting is a UL Recognized Component (identifiable by the RU symbol). UL Recognized Components must be factory installed in a Certified (Listed) product such as a luminaire or ceiling fan in which the combination of the male attachment fitting and the luminaire or fan are evaluated as part of the Certification (Listing) of the overall product.

The combination of the male attachment fitting powering the overall luminaire or fan together with the receptacle is evaluated for weight, intended orientation, temperature, maintaining electrical enclosure integrity and other criteria specific to each application.

The female receptacle is Certified (Listed) under the product category Receptacles for Plugs and Attachment Plugs, (RTRT). The UL guide information and Certifications (Listings) can be located on UL Product Spec at; enter RTRT at the category code search.

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