Develop an effective industrial equipment SCCR strategy
Technology Update: Short-Circuit Current Rating (SCCR) compliance requires attention to multiple considerations. See the SCCR regulations. Online extra: Below, learn five steps to define equipment SCCR.
To meet equipment short-circuit current rating (SCCR) needs, there are many considerations. In addition to regulatory and code requirements, protecting against short-circuit events is critical to enhancing workplace safety and protecting equipment. Original equipment manufacturers (OEMs) can play a crucial role in helping customers understand and plan for appropriate equipment SCCR levels.
This effort can yield powerful short- and long-term business advantages by enhancing safety, minimizing risk, and reducing costs. General discussion that raises awareness of equipment SCCR requirements can help establish the protection levels needed to support a safe working environment. A solid equipment SCCR plan can minimize risks and save customers the time and costs in the long term, even as utility upgrades, maintenance, equipment relocation, and other factors impact available fault current levels. Effective SCCR plans also help avoid oversized components and increased material costs.
SCCR requirements apply to control panels used to operate machinery and equipment. Although protection from short-circuit events in electrical switchgear and distribution equipment is often properly specified and applied, these same requirements are often misunderstood or misapplied in machinery and equipment. The Occupational Safety and Health Administration (OSHA) and the National Electrical Code (NEC) require sufficient equipment short-circuit current ratings of control panels at the point of installation to protect equipment and personnel from certain risks in the event of a short circuit.
Summary code, regulations
- The NEC requires industrial control panels be marked with the equipment SCCR (Sections 409.110, 670.3(A), 440.4(B)).
- NEC 110.10 requires that electrical equipment is sufficient for the available fault current.
- OSHA regulation (Section 1910.303(b)(5)) requires all electrical equipment, including equipment that is already installed and new equipment being installed, meet this requirement. OSHA does not provide for any exemptions.
- The NEC (Section 409.22) prohibits installing industrial control panels in locations where available fault current exceeds the equipment's short-circuit current rating.
5 kA equipment design limits
Manufacturers of industrial control panels and machinery face a difficult task when it comes to standardizing an equipment SCCR design; one that works for one industry or application may not work for others. Installation sites can vary widely with differing equipment SCCR needs. The required equipment SCCR can even vary within the same facility, depending on its location in the electrical distribution system.
With so much variation, how can a machinery OEM arrive at an acceptable equipment SCCR strategy? If a control panel manufacturer chooses to standardize on 5 kA equipment SCCR for all designs, and only designs a higher equipment SCCR when required, significant design changes may be necessary to meet a new equipment SCCR need. Often this results in reengineering efforts and increased material costs. Another risk of standardizing a 5 kA equipment SCCR is revealed if it is found to be inadequate after it is installed; a scenario that may not be easily corrected.
An effective strategy strives to achieve the necessary equipment SCCR for the majority of installations with minimal costs, resources, and effort. No one plan works for every industry or application. Each manufacturer must carefully consider the various factors when developing its equipment SCCR strategy. To develop an effective strategy:
- Understand available fault current and the range typically encountered in an industry
- Define an equipment SCCR level that best meets the majority of these installations
- Develop and compare designs at this equipment SCCR level and the worst case scenario (highest fault current) to determine the difference in cost, installation, and features
- Standardize an equipment SCCR design that best meets the largest range of application requirements
- Validate and document the industrial control panel's SCCR.
With the right tools and resources, defining a competitive solution that meets equipment SCCR is attainable. Consider component SCCR selection tools or equipment SCCR calculators when developing equipment SCCR solutions.
Developing an equipment SCCR plan can yield significant benefits for the OEM. A carefully considered equipment SCCR strategy not only avoids excessive reactive costs (engineering time, costly material changes, project delays), but also helps differentiate from competition, as well as enhances personnel safety.
Learn more about five steps to define equipment SCCR.
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