The standard regulates component spacing, wire bending space, and protection against overheating. Summary of Key Changes (3rd Edition vs. 2nd Edition) 2nd Edition (2013/2017) 3rd Edition (2018-Present) SPDs Limited requirements Detailed requirements added MPCBs Standard coverage Expanded requirements for motor protection Transformers Conventional New options for "current limiting" transformers Effectivity Prior to 2020 Required as of July 1, 2020 Conclusion
[Determine Load Requirements] ➔ [Size Power & Branch Circuits] ➔ [Calculate System SCCR] ➔ [Design Enclosure & Thermal Controls] ➔ [Apply Final Labeling] Ul 508a 3rd Edition Pdf