CSA C22.2 No. 248.8-11 (2016): Technical Specifications for Class G Low-Voltage Fuses

Scope and Purpose

CSA C22.2 No. 248.8-11 (2016) is a bi-national harmonized standard that provides detailed requirements for Class G low-voltage fuses and fuseholders intended for use in Canada. As part of the larger C22.2 series of the Canadian Electrical Code (CE Code), this standard specifically addresses fuses rated at 600 V or less, with current ratings up to 60 A, used for branch circuit overcurrent protection. Class G fuses are distinguished by their compact dimensions and high interrupting capacity, making them suitable for both residential and commercial applications where space is constrained and fault currents are moderate.

The standard is harmonized with UL 248-8 and NOM-031-SCFI, ensuring that products meeting this standard can be marketed across North America with appropriate national markings. It covers fuse construction, electrical and mechanical performance, testing procedures, and marking requirements necessary to comply with the CE Code (CSA C22.1).

Technical Requirements

Ratings and Dimensions

Class G fuses are available in standard ampere ratings from 0.5 A to 60 A at voltages up to 600 V AC/DC. The standard defines specific dimensional envelopes to guarantee interchangeability between manufacturers. Table 1 lists the key dimensions for typical Class G fuse sizes.

Table 1 – Typical dimensions and ratings for Class G fuses per CSA C22.2 No. 248.8-11 (2016).

Construction and Materials

The standard mandates that fuses be constructed with materials that provide reliable performance under normal and fault conditions. Fuse bodies must be of ceramic or other non‑combustible material capable of withstanding the thermal and mechanical stresses during operation. End caps and contacts must be corrosion‑resistant and provide low‑resistance connections. Internal elements (e.g., silver, copper, or alloy strips) must be precisely designed to melt within prescribed time‑current characteristics.

For fuseholders, CSA C22.2 No. 248.8-11 specifies spacing, insulating material requirements, and minimum creepage distances to ensure safety when the fuse is being replaced. Fuseholders must accept only Class G fuses and incorporate features that prevent the insertion of fuses of higher current or voltage ratings.

Performance Tests

Products must pass a series of rigorous tests to demonstrate compliance:

• Overload test – Fuse must carry 200 % of rated current for a specified period without opening.
• Temperature rise test – At rated current, temperature rises must not exceed 60 K above ambient at the fuseholder terminals.
• Dielectric voltage withstand test – 1,500 V applied for 60 s without breakdown (between live parts and mounting surfaces).
• Interrupting capacity test – Fuse must safely interrupt an rms symmetrical current equal to its interrupting rating (typically 10 kA) at rated voltage.
• Endurance test – For fuseholders, a cyclic on‑off test at rated current must demonstrate mechanical durability.

Implementation Highlights

Application in Canadian Electrical Installations

Class G fuses are commonly used in branch circuits of lighting, heating, and motor control panels where a compact, current‑limiting fuse is beneficial. Their small size makes them suitable for modular control panels and distribution boards where space is at a premium. According to Rule 14-200 of the CE Code, Class G fuses are permitted for general branch‑circuit overcurrent protection as long as the installation complies with the product standard.

When selecting Class G fuses, consider the load characteristics:

• For inductive loads (motors, transformers), the fuse rating should allow for inrush currents without nuisance opening. A time‑delay design (Class G with time‑delay element) is recommended.
• For resistive loads (heaters, lighting), standard Class G fuses provide adequate protection.
• For mixed loads, consult the manufacturer’s coordination curves.

Table 2 – Typical applications and recommended Class G fuse selections.

Testing and Certification

Before a Class G fuse or fuseholder can be marked with the CSA logo, manufacturers must submit samples to an accredited certification body such as CSA Group, UL, or Intertek. Testing includes all performance and safety tests detailed in the standard. Additionally, factories are subject to periodic follow‑up inspections to ensure production consistency. Products that pass are listed in the CSA’s product directory and may bear the CSA or NRTL mark.

Compliance Notes

Marking Requirements

Each fuse must be permanently marked with:

• Manufacturer’s name or trademark
• Ampere rating (e.g., “20 A”)
• Voltage rating (e.g., “600 V”)
• Interrupting rating (e.g., “10 kA”)
• Class designation “G”
• CSA certification mark

Fuseholders must be marked with the same information and also indicate the maximum allowable fuse rating and the rated voltage.

Coordination with Overcurrent Devices

For selective coordination in downstream circuits, Class G fuses can be coordinated with other fuses or circuit breakers at the panel. However, the current‑limiting behavior of Class G fuses (due to their fast‑acting element) means that they typically open within the first half‑cycle under fault conditions. This limits the let‑through energy and helps protect downstream components.

Revisions and Updates

The 2016 edition (CSA C22.2 No. 248.8-11) revised earlier editions to align with UL 248-8 and introduced new requirements for DC testing, improved temperature‑rise limits, and updated reference standards. Manufacturers should always refer to the latest edition to ensure ongoing compliance. A summary of changes from previous editions can be obtained from CSA Group’s standards store.

Article prepared for informational purposes. Always refer to the official CSA C22.2 No. 248.8-11 (2016) document for complete requirements. © 2026