CSA C22.2 No. 248.10-11 (2017): Technical Guide to Class L Low-Voltage Fuses

CSA C22.2 No. 248.10-11 (2017) is a Canadian national standard of Canada from the CSA Group that specifies the requirements for Class L low-voltage fuses. These fuses are used for overcurrent protection in electrical circuits, typically with current ratings of 600 A and above and voltages up to 600 V AC/DC. The standard is harmonized with UL 248-10 and is referenced in the Canadian Electrical Code, Part I (CSA C22.1). This article provides an in-depth look at the scope, technical requirements, implementation considerations, and compliance aspects of this important safety standard.

Scope and Application

This standard applies to Class L fuses rated for:

• Maximum voltage: 600 V AC / 300 V DC (or 600 V DC if specified)
• Current range: 600 A to 6000 A
• Interrupting rating: up to 200 kA RMS symmetrical AC
• Frequency: 50/60 Hz

These fuses are intended for protection of service equipment, feeders, and busways where high fault currents may be present. They are characterized by their bolt-in mounting, current-limiting capability, and dimensions that ensure non-interchangeability with lower-rated fuses.

Technical Requirements and Performance Criteria

Key requirements include:

• Construction: Fuse bodies must be made of material with suitable mechanical and electrical insulating properties. They must be filled with arc-quenching material.
• Time-Current Characteristics: The standard defines minimum and maximum melting and clearing times at various overcurrent levels, with specified test points.
• Interrupting Rating: Fuses must clear the maximum fault current without external damage, with proper coordination.
• Overload and Endurance: The
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