Short-Circuit Current Rated (SCCR) Power Distribution Blocks We offer distinctly different styles of short-circuit current rated (SCCR) power distribution blocks (PDBs) and terminal blocks (TBs) to match different application needs. The differences are whether the power distribution blocks are enclosed or not, and whether they are UL1953 Listed PDBs or UL1059 Recognized TBs, which have different minimum spacing requirements.
Why is this important?
- Assembly short-circuit current ratings (SCCRs) are now required in the 2005 NEC® and UL508A Listed Industrial Control Panels.
- Marking the SCCR on Industrial Control Panels (NEC® 409.110), Industrial Machinery Electrical Panels (NEC® 670.3(A)), and HVAC equipment (NEC® 440.4(B)) is now required by the National Electrical Code.
- Power distribution blocks or terminal blocks not marked with an SCCR are typically one of the weakest links and may limit an assembly to no more than 10 kA SCCR.
- The EPDB series and HPB series power distribution blocks have increased spacing required where used in feeder circuits in equipment listed to UL508A. The PB series UL1059 terminal blocks must be evaluated for proper spacing.
- Also, for building wiring systems, the EPDB series and HPB series power distribution blocks can be used to meet the 2005 NEC® requirements in section 376.56(B) for power distribution blocks in wireways.