Change Summary

• A new exception has been added covering SPDs and other similar devices only if in accordance with manufacturer’s instructions
• The revision clarifies what type of equipment the tap conductors must terminate in
• The words “equipment containing an overcurrent” have been added in front of the word “device(s)” in b

Expert Analysis

This section now clarifies what was meant by the word “device” as previously used in b. Information provided in the substantiation indicated that The word “device” should be replaced with more descriptive terms since the definition of device is, “A unit of an electrical system that carries or controls electric energy as its principal function.” Though obviously not intended by 240.24(B)(1)(1) b, the broad definition of device includes wire and other conductors such as busway. Revising the section to reference equipment containing overcurrent device(s) narrows the application of the section beyond what the previous wording literally meant. Action by Code Making Panel-10 on Comment 10-14 also refines the exception and expands it slightly to apply to surge protective devices (SPDs) and other similar equipment that may be connected by a tap in accordance with the provisions of this section. The revision and new exception improve clarity and promote more consistent application of the 10-foot tap rules. Similar revisions have also been incorporated into 240.21(C)(2) which addresses transformer secondary conductors.
 

Leviton Comment

Article 240.21(B)(1)(1)b accommodates the use of Surge Protection Devices (SPDs).  Type 2 SPDs would typically be the type of device associated with this Code article.

Explanation of the different levels of surge protection and their applications.

Type 1 SPD for the supply side of service entrance. Leviton offers several options including the 55240-ASA and 50240-MSA secondary surge arrestors

Type 2 SPDs are typically service entrance SPD panels or branch circuit SPD panels that are connected on the load side of the service disconnect overcurrent device (main service panel).  Leviton offers several options including the 52120-7CS.

Type 3 SPD’s are typically surge receptacles or cord connected point-of use devices. Leviton offers a complete assortment in duplex, quad and 6-plex in many styles and colors.

Type 4 SPDs: Are component assemblies consisting of one or more Type 5 components together with a disconnect (integral or external) or a means of complying with the limited current tests in UL 1449.

Type 5 SPDs: Discrete component surge suppressors connected by its leads or provided with an enclosure with mounting means and wiring terminations.

Type 1 and Type 2 SPDs shunt external surges that originate from utilities or disturbances outside the home or facility.  Type 2 SPDs can protect for both internal and external surges when located at the branch. Type 3 SPDs can shunt surges that originated internally within the home or facility. So a comprehensive strategy for surge protection typically involves a Type 1 or Type 2 SPD and also a Type 3 SPD at point of use.