Effective March 2014 Application Paper AP01200004E Supersedes December 2009 Application of multi-wire terminals for molded-case circuit breakers Circuit breakers equipped with multi-wire terminals Abstract function as feeder breakers, as opposed to branch Multi-wire terminals for molded-case circuit breakers. Feeder circuits can be tapped, while breakers are a means to provide more than one branch circuits cannot. load side termination while maintaining the circuit breakers ULT listing. This paper examines the Codes and standards application of multi-wire terminals in conjunction with UL Standard 508A as well as with the National requirements Electrical CodeT, NFPAT 70-2014 (NECT). The paper NEC requirements addresses multi-wire terminals used with circuit breakers in industrial control panels as defined in NEC Section 430.28 addresses the topic NEC Section 409 and UL Standard 508A. of feeder taps. Multi-wire terminals 430.28 Feeder TapsFeeder tap conductors shall have an ampacity not less than that required by The tables below list field-installed, multi-wire Part II (Part II addresses the sizing of conductors terminals for Eaton breakers. These are UL listed for specific loads consult the NEC for details), for installation on the load side (only) of the shall terminate in a branch-circuit protective corresponding circuit breaker. It is important to device, and, in addition, shall meet one of the note that each load conductor must be sized in following requirements: order to provide the proper ampacity to meet the circuit breakers handle rating, or be protected by a 1. Be enclosed either by an enclosed controller properly sized individual overcurrent device. Under or by a raceway, be not more than 10 feet these conditions, the installed multi-wire terminal (3.0m) in length, and, for field installation, be will maintain the marked short-circuit current rating protected by an overcurrent device on the line of the breaker. side of the tap conductor, the rating or setting of which shall not exceed 1000 percent of the Table 1. Series CT Breakers tap conductor ampacity. Max. Wires Per Wire Size Kit 2. Have an ampacity of at least 1/3 that of the Frame Amperes Terminal Range AWg Catalog No. feeder conductors, be suitably protected from G 100 3 142 3TA100G3K physical damage or enclosed in a raceway, and G 100 6 146 3TA100G6K be not more than 25 feet (7.5m) in length. F 225 3 142 3TA150F3K 3. Have an ampacity not less than the feeder F 225 6 146 3TA150F6K conductors Reference 1 . J 250 3 142 3TA250J3K UL 508A requirements J 250 6 146 3TA250J6K UL 508A Section 31.4 addresses the issue K 400 3 122/0 3TA400K3K using similar language. K 400 6 143 3TA400K6K Section 31.4.3The ampacity of the tap conductors, the internal conductors to the Table 2. Series GT Breakers individual loads, shall be: Max. Wires Per Wire Size Kit a. Not less than 1/3 the ampacity of the branch Frame Amperes Terminal Range AWg Catalog No. circuit conductor, calculated as in 28.3.3 EG 125 3 142 3TA125E3K (28.3.3 addresses the sizing of field-wiring EG 125 6 146 3TA125E6K conductors for specific loads. Consult UL 508A JG 250 3 142 3TA250FJ3 for details.) or JG 250 6 146 3TA250FJ6 b. Not less than 1/10 the ampere rating of the LG 600 6 141/0 3TA600L6K branch circuit protection for the group for each motor circuit provided with a manual motor controller marked Suitable as tap conductor protection in group installations and complies with the Standard for Industrial Control Equipment, UL 508. The conductors on the load side of the manual motor controller shall have an ampacity not less than calculated in 28.3.2 (28.3.2 addresses the sizing of field- wiring conductors for motor loads consult UL 508A for details) Reference 2 .Application Paper AP01200004E Application of multi-wire terminals Effective March 2014 for molded-case circuit breakers NEC 430.28 (1) and UL 508A 31.4.3 (b) state the same requirement Conclusion in different terms. Both agree, however, that a tap conductor no more Multi-wire terminals can offer significant advantages in the than 10 feet (3.0m) long, emanating from a multi-wire terminal (tap), construction of industrial control panels. must have an ampacity equal to at least 10 percent of the ampacity of the feeder breakers trip current. Some term this the 10-foot tap rule. 1. While a combination of a circuit breaker and a power terminal Likewise, NEC 430.28 (2) and UL 508A 31.4.3 (a) state the same block must be tested for a combined short-circuit current rating, requirement for tap conductors up to 25 feet (7.5m) long, sometimes a multi-wire terminal is a listed circuit breaker accessory, carrying termed the 25-foot tap rule. A tap conductor up to 25 feet (7.5m) the same short-circuit current rating as the breaker. long must have an ampacity equal to at least 1/3 the ampacity of 2. A multi-wire terminal is mounted on the circuit breakers load- the feeder breakers trip current. side terminals, saving expensive panel space, mounting time, and wiring time. Sizing conductors 3. A circuit breaker can have a multi-wire terminal factory-mounted, saving labor for the panel manufacturer. Application complying with UL 508A 10-foot tap rule References The ampacity for a tap conductor applied to a 200A circuit breaker 1. NFPA 70, the National Electrical Code (2014). must be equal to 20A or greater. Referring to Table 28.1 in UL 508A, Quincy, MA: National Fire Protection Association. the conductor would have to be at least 12 AWG. The conductor 2. UL 508A (2013). Northbrook, IL: Underwriters Laboratories. must terminate in an appropriately sized overcurrent protective device, for example, a circuit breaker or fuse. 25-foot tap rule The ampacity for a conductor not exceeding 25 feet (7.5m) in length must be at least 1/3 the ampacity of the circuit breakers trip rating. The ampacity for a tap conductor applied to a 300A circuit breaker must be equal to 100A or greater. Referring to Table 28.1 in UL 508A, the conductor would have to be at least 3 AWG. The conductor must terminate in an appropriately sized overcurrent protective device, for example, a circuit breaker or fuse. Size range of conductors While a wide range of conductors is listed for a particular multi-wire terminal, the entire range may not apply to every breaker frame to which a terminal is affixed. A K-frame breaker, for example, can have trip ranges from 70 to 40A. While a 14 AWG conductor may be applied to a 70A trip unit, it may not be applied to a 400A trip unit. Proper selection must be made as noted in the rules elucidated in the application sections above. Conductor temperature ratings Circuit breaker terminals are rated for a maximum temperature of 75C. Attention must be paid to conductor temperature ratings and the corresponding ampacities tabulated in the appropriate standard. Table 28.1, UL 508A, contains columns for conductor temperatures of 60C and 75C. Either is within the range of the multi-wire terminal temperature rating. While NEC Table 310.15 (b) (16) contains like ratings, it also contains columns for 90C and higher. Conductors having higher temperature ratings, such as 90C, may be used however, the ampacity must be de-rated to that in the 75C column. Eaton 1000 Eaton Boulevard Cleveland, OH 44122 United States Eaton.com 2014 Eaton Eaton is a registered trademark. All Rights Reserved Printed in USA All other trademarks are property Publication No. AP01200004E / Z15014 of their respective owners. March 2014