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CSA C22.2 No. 4248.15-07 (R2016): Technical Requirements for Class T Fuses in Canada
Specifications, Testing, and Compliance for High-Rupturing-Capacity Fuses
Class T fuses are compact, high-rupturing-capacity (HRC) current-limiting fuses designed for use in circuits requiring high fault current protection. In Canada, the requirements for these fuses are specified in CSA C22.2 No. 4248.15-07 (R2016), a National Standard of Canada developed under the Canadian Electrical Code, Part I (CE Code). This article provides an overview of the standard, its technical requirements, and guidance for compliance and implementation.
Scope and Application
CSA C22.2 No. 4248.15-07 applies to Class T fuses rated up to 600 A, for use in alternating current (AC) circuits up to 600 V and direct current (DC) circuits up to 300 V. These fuses are intended to provide overcurrent protection in accordance with Section 14 of the CE Code and have a minimum interrupting rating of 200 kA RMS symmetrical for AC, and 100 kA for DC. The standard covers fuses and their fuseholders (fuse carriers and bases) for use in electrical equipment such as panelboards, switchboards, motor control centers, and power distribution units.
Class T fuses are time-delay fuses characterized by their compact size compared to other classes, making them suitable for applications where space is limited. The standard was originally published in 2007 and reaffirmed in 2016, confirming its continued validity.
Tip: Class T fuses are often used as main feeders or branch circuit protection in commercial and industrial settings where high fault currents are expected. Their current-limiting action reduces energy let-through, protecting downstream components.
Technical Requirements
Ratings and Dimensions
The standard specifies electrical ratings, dimensional requirements for fuse bodies and fuseholders, as well as performance test procedures. The following table summarizes the typical ratings and maximum dimensions for common Class T fuses.
| Ampere Rating (A) | AC Voltage Rating (V) | DC Voltage Rating (V) | Max. Overall Length (mm) | Max. Diameter (mm) |
|---|---|---|---|---|
| 1–30 | 600 | 300 | 32.0 | 10.4 |
| 31–60 | 600 | 300 | 38.0 | 14.3 |
| 61–100 | 600 | 300 | 44.5 | 19.1 |
| 101–200 | 600 | 300 | 54.0 | 25.4 |
| 201–400 | 600 | 300 | 64.0 | 32.0 |
| 401–600 | 600 | 300 | 76.0 | 38.1 |
Note: Dimensional tolerances and detailed interchangeability requirements are defined in the standard to ensure non-interchangeability with other fuse classes except Class T.
Performance Requirements
The standard outlines several mandatory tests to verify the safety and performance of Class T fuses:
- Temperature rise and power dissipation: Fuses must carry 100% of rated current without exceeding a specified temperature rise limit (typically 75 °C above ambient) at rated voltage.
- Overcurrent test: Fuses must open at 200% of rated current within a maximum time (e.g., 120 s for time-delay fuses) to ensure proper coordination.
- Endurance test: For DC ratings, fuses undergo a 50-cycle endurance test at 110% of rated DC voltage.
- Interrupting capacity: Fuses and fuseholders must safely interrupt currents up to 200 kA RMS symmetric AC and 100 kA DC without ejection of hazardous materials or sustained arcing.
- Time-current characteristics: Time-delay fuses must not open within a specified short-time window (e.g., 10 s at 500% rated current for some classes) to allow harmless inrush currents.
Caution: While Class T fuses are non-interchangeable with other fuse classes, they can be substituted only in approved Class T fuse holders that meet the dimensional requirements of CSA C22.2 No. 4248.15-07. Always verify fuse holder certification to the same standard.
Implementation and Certification Highlights
To sell or install Class T fuses in Canada, they must be certified to CSA C22.2 No. 4248.15-07 by a recognized certification organization such as CSA Group, UL, or Intertek. Key aspects of certification include:
- Marking: Each fuse shall be legibly and permanently marked with the manufacturer’s name or trademark, catalog number, ampere rating, voltage rating, interrupting rating, and the certification mark.
- Fuseholder acceptance: Fuseholders are considered part of the fuse assembly; they must be tested and listed together. A certified fuseholder is mandatory to maintain the assembly’s interrupting rating.
- Cooperativity with the CE Code: The standard is referenced in the CE Code for applications where Class T fuses are required or permitted (e.g., in commercial cooking equipment, air‑conditioning equipment).
Compliance tip: When specifying Class T fuses, always ensure they are from a source with current CSA certification. Reaffirmation (R2016) means the standard is still active; always check for the latest edition (e.g., CSA C22.2 No. 4248.15-18 if available).
Compliance Notes and Industry Relevance
- Integration with UL standards: This CSA standard is harmonized with UL 248-15 (Standard for Class T Fuses). Canadian and US manufacturers often design products to meet both simultaneously.
- Revision timeline: The 2007 edition (reaffirmed in 2016) is currently the latest national standard. However, a newer edition (R2022) may have been published; always verify the effective date with the local inspection authority.
- Field testing: In cases where certified equipment is not available, special field evaluation by accredited agencies such as CSA Group can be performed to grant equivalency or permission for use.
All technical content is current as of 2026.
Frequently Asked Questions
Q: What is the difference between Class T and Class J fuses?
A: Both are current-limiting fuses, but Class T fuses are physically smaller and have limited DC ratings (300 V max vs 600 V DC for Class J). Class T fuses have a high interrupting rating (200 kA AC) and are primarily used for feeder and branch circuit protection in industrial control panels where space is at a premium.
A: Both are current-limiting fuses, but Class T fuses are physically smaller and have limited DC ratings (300 V max vs 600 V DC for Class J). Class T fuses have a high interrupting rating (200 kA AC) and are primarily used for feeder and branch circuit protection in industrial control panels where space is at a premium.
Q: Can Class T fuses be used in Canada for solar photovoltaic systems?
A: Yes, Class T fuses are often used in PV combiners and inverters under the CE Code, provided they are rated for DC applications and installed in accordance with manufacturer instructions. Always check that the DC voltage rating covers the maximum open-circuit voltage (Voc) of the PV string.
A: Yes, Class T fuses are often used in PV combiners and inverters under the CE Code, provided they are rated for DC applications and installed in accordance with manufacturer instructions. Always check that the DC voltage rating covers the maximum open-circuit voltage (Voc) of the PV string.
Q: Is field replacement of a Class T fuse with another class permitted?
A: No. Due to unique dimensional and performance characteristics, only Class T fuses can be inserted into Class T fuseholders. Substitution with another class is unsafe and violates the equipment listing.
A: No. Due to unique dimensional and performance characteristics, only Class T fuses can be inserted into Class T fuseholders. Substitution with another class is unsafe and violates the equipment listing.
Q: How can I verify the certification status of a Class T fuse?
A: Look for the certification mark (CSA, UL, etc.) on the fuse body. Additionally, manufacturer data sheets should list the standard reference. Online directories of certified products are maintained by CSA Group and other certifiers.
A: Look for the certification mark (CSA, UL, etc.) on the fuse body. Additionally, manufacturer data sheets should list the standard reference. Online directories of certified products are maintained by CSA Group and other certifiers.