Requirements for machine approval in North America under the new NEC 2017
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Requirements for machine approval in North America under the new NEC 2017

The NEC 2017 introduces increased requirements for SCCR Rittal has long been prepared Rittal always responds promptly to the latest international requirements with suitably adapted, standard-compliant products and up-to-date knowledge for seamless compliance with the latest standards in enclosure manufacturing. SCCR ratings of up to 65 kA are anticipated Surveys show that more than half of all machine manufacturers design their products for the North American market with the minimum SCCR (Short Circuit Current Rating) of 5 kA. Publication of the NEC 2017 means there is a greater risk that...

Requirement for machine approvals in the USA and Canada Compliance with UL 508A In the USA and Canada, a machine or plant cannot be commissioned until approved by the AHJ (Authority Having Jurisdiction). The AHJ verifies compliance with the valid regulations in that state, such as the National Electric Code NEC (NFPA 70) or the NFPA 79 Electrical Standard for Industrial Machinery. In practice, approval of the equipment to standard UL 508A provides the required verification. Without verification, the AHJ will not usually issue an operating permit. UL 508A combines the applicable requirements...

All components used in the enclosure, including the climate control and the housing, must have suitable UL approval. UL 508A The area outlined in magenta specifically considers the requirements of UL 508A for electrical control cabinets. The method outlined in Annex SB is a recognised procedure for determining the SCCR, whose importance is growing with the NEC 2017. NEC 2017 requirement for short-circuit withstand strength of enclosures at the infeed point The system’s SCCR must be greater than or equal to the SCCR at the supply end. National Fire Protection Association NFPA 79 applies to...

SCCR under UL 508A Fundamental principles Key terms and regulations When determining the SCCR, for example in conjunction with the use of busbars, first of all it is important to be familiar with the commonly used components, terms and regulations. The following sections therefore address these framework parameters, with reference to Standard UL 508A Second Edition, including revisions, dated July 31,2017. Feeder Circuit The feeder circuit is subject to increased requirements on creepage distances and clearances. The feeder circuit includes all devices which, viewed from the load side, are...

SCCR regulations Which short circuit-limiting protective and switching devices SCPD can be used in the feeder circuit to increase the SCCR? Short circuit-limiting protective devices (hereinafter referred to as SCPD) may be used to increase the SCCR value of an enclosure. If the peak let-through of an SCPD (feeder fuse/feeder breaker) is less than the SCCR of the component in question in the branch circuit, the SCCR of this component may be raised to the feeder SCCR under consideration. The following components may be used as SCPD: I Circuit breaker, moulded case and circuit breaker...

Important for UL 508A: Short-circuit withstand strength SCCR to the lowest common denominator Determining the overall SCCR in the enclosure When determining the SCCR (Short Circuit Current Rating), it is a matter of determining which components or tested combinations in the main circuits inside the enclosure have the lowest SCCR. The lowest individual SCCR determines the SCCR of the overall enclosure (overall SCCR). An enclosure’s SCCR ultimately determines whether the application’s short-circuit withstand strength requirements match the available SCCR from the power supply. This usually...

components in the power circuit List of devices that do not fall under the SCCR approach Determining the SCCR using the rating plate or manufacturer documentation of the device/component Determining the SCCR in accordance with Table SB4.1 Determining the SCCR by testing to UL 508 SB4.3 Ascertain the feeder components that may be used to limit the short-circuit. SB4.4 Determine the overall SCCR of the enclosure 4.3.1 Short circuit current-limiting with a transformer in the feeder 4.3.2 Increasing the SCCR by using a current-limiting circuit-breaker in the feeder 4.3.3 Increasing the SCCR by...

Practical example SCCR including a busbar assembly Busbars are a standard feature in modern enclosure assembly. RiLine systems are all tested for an SCCR of 65 kA. This therefore eliminates the need for time-consuming verification. The user need only be concerned with SCCR compliance by the top-mounted equipment. Here is an example of SCCR in busbar systems.

SV 9340.050 65 kA, 480 V with circuit breaker CCN: DIVQ max. 600 A SV 9345.710 65 kA, 480 V with circuit breaker CCN: DIVQ max. 600 A SV 9342.510 65 kA, 480 V with circuit breaker CCN: DIVQ max. 125 A SV 9340.310 65 kA, 480 V with manual motor controller CCN: NLRV max. 30 A SV 9340.390 65 kA, 480 V with manual motor controller CCN: NKJH max. 30 A SV 9340.310 65 kA, 480 V with Class CC fuseholder CCN: JDDZ max. 30 A

All RiLine systems have been tested for an SCCR of 65 kA. This therefore eliminates the need for time-consuming verification. The user need only be concerned with SCCR compliance by the top-mounted equipment.

UL-tested Rittal components RiLine busbars Ideal for international use with an approved, cULus listed 60 mm busbar system. The RiLine 60 mm busbar system from Rittal has cULus-listed approval. This approval offers clear advantages for international machinery and plant manufacturers with target markets in the USA or Canada: Minimal design input, simplified sign-off of plant by UL (Underwriters Laboratories) and CSA (Canadian Standards Association), and therefore most importantly, no need to test for compliance with the Conditions of Acceptability (COA) of all the UL-recognized components...

RiLine busbars Excerpt Initial overview of UL 508A-compliant RiLine busbars and components The following table lists all the key products covered by the 65 kA SCCR, but does not include all UL-listed items from the RiLine product range. Distance between busbar supports mm