Mersen HSJ125 Class J Time-delay Fuse 125A

Product Description

The MERSEN HSJ125 is a 125-amp Class J time-delay fuse designed for branch circuit and equipment protection in commercial and industrial electrical systems. Class J fuses provide current-limiting performance, interrupting fault currents quickly to protect downstream components including motors, transformers, and panel boards. The HSJ125 fits standard Class J fusible disconnects and loadcenters. Licensed electricians install this fuse as part of overcurrent protection schemes governed by the National Electrical Code. Its time-delay characteristic allows motors and other inductive loads to start without nuisance blowing while still providing fast response to sustained overloads and short circuits.

The HSJ125 is suited for use in commercial HVAC equipment, motor control centers, industrial machinery, and branch circuit protection panels where Class J fusing is specified. It is a common choice when upgrading from non-current-limiting fuse types to meet modern code requirements or when replacing a blown protective fuse in a fusible disconnect switch rated for Class J elements.

Key Features

• 125-amp continuous current rating for branch circuit overcurrent protection
• Class J current-limiting design for fast fault interruption
• Time-delay characteristic accommodates inductive motor start-up inrush
• Compact form factor fits standard Class J fusible disconnect holders
• Single fuse per pack

Compatibility

Designed as an OEM-style replacement for Class J fusible disconnect switches and loadcenters rated to accept 125-amp Class J fuses.

Installation Notes

Installation must be performed by a licensed electrician in accordance with applicable National Electrical Code requirements. De-energize and lock out the circuit at the upstream overcurrent device before removing or installing the fuse. Verify that the fusible disconnect or fuse holder is rated for Class J fuses and for the required voltage and ampere rating before inserting the fuse. Never install a fuse with a higher ampere rating than the circuit or equipment is designed to handle.