Mersen Launches Class J Critical Power Panelboard for Critical Systems

Mersen has launched the Class J Critical Power Panel series, expanding its portfolio of configurable low-voltage power distribution equipment. The system provides electrical circuit protection for mission-critical infrastructure, including data centers, uninterruptible power supply topologies, medium-voltage electrical houses, utility DC operations, and rail transit networks.

Selective Coordination and Compliance Standards in Critical Facilities
Electrical system designers face strict regulatory mandates under the National Electrical Code for emergency facilities. Standards including NEC 700.27 for emergency systems and NEC 701.18 for legally required standby equipment mandate selective coordination across all overcurrent devices down to the fault source. Circuit breaker configurations often require complex time-current curve evaluations and digital trip units that remain vulnerable to miscoordination during high-magnitude short circuits.

The Class J Critical Power Panel addresses these isolation challenges by utilizing current-limiting fuses that clear high-fault currents in less than a half-cycle. This level of current limitation minimizes let-through thermal and mechanical stress on upstream distribution gear. The panelboard carries a UL 67 listing and achieves a short-circuit current rating up to 200 kA when backed by up to a 400A main fuse, facilitating compliance with selective coordination mandates across the entire overcurrent range.

Hardware Topology and Electrical Characteristics
The panelboard operates at ratings up to 600 VAC or 125 VDC, covering both alternate current distribution and direct current auxiliary supply lines. Primary switching is handled by switched fused mains rated up to 400A, which incorporate UL 98-rated Compact Fused Disconnect units alongside Amp-Trap 2000 Class J branch protection. Branch positions accommodate electrical loads up to 30A for lighting circuits and auxiliary machinery.

Mechanical construction centers around a patented Z-profile bus bar configuration mounted against a steel backplate. This layout minimizes internal bolted connections to decrease potential mechanical and electrical thermal failure points within the chassis. The hardware footprint includes options for integral surge protection devices, feed-through lugs, and standard dual or sub-feed lugs on main-lug-only mains to simplify installation within space-constrained electrical enclosures.

Additional Context:
This section details technical specifications and competitive benchmarking not included in the original product announcement

Fused distribution panelboards directly challenge standard thermal-magnetic and electronic trip molded case circuit breaker panelboards manufactured by Eaton (Pow-R-Line series), Schneider Electric (Square D NQ and NF series), and ABB (ReliaGear). While circuit breaker panelboards offer resettable overcurrent mechanisms, achieving 200 kA short-circuit current ratings typically requires expensive, fully tested series ratings or current-limiting breakers with restrictive let-through profiles.

Within the dedicated fused panel segment, the primary industry benchmark is the Bussmann series Quik-Spec Coordination Panelboard from Eaton. The Quik-Spec platform utilizes finger-safe Class CF (CUBEFuse) branch devices to achieve a 200 kA short-circuit current rating in a compact layout, relying on a proprietary fuse footprint.

Mersen's deployment of a standard Class J form factor provides an open physical configuration compliant with standard Class J dimensional envelopes. This enables electrical maintenance teams to interchange standard time-delay or fast-acting Class J branch fuses from different manufacturers without altering the internal mounting base, balancing high interrupting capacity with standardized component replacement.

Edited by Natania Lyngdoh, Induportals editor, assisted by AI.

www.mersen.com