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CSA C22.2 No. 4248.6-07 (2017) – Technical Requirements for Supplementary Fuses in Photovoltaic Systems
Understanding the Canadian Standard for PV Fuse Protection
Scope and Application
CSA C22.2 No. 4248.6-07 (R2017) is the Canadian adoption of IEC 60269-6 with national modifications for supplementary fuses used in photovoltaic (PV) systems. This standard applies to fuse-links, fuse holders, and fuse accessories designed for DC circuits in PV arrays, inverters, and battery storage systems. The rated voltage is limited to 1,000 V DC, rated currents up to 250 A, and breaking capacity up to 50 kA. These fuses are intended for supplementary protection—i.e., protecting cable assemblies, combiner boxes, and individual string conductors against overloads and short-circuits. The standard excludes branch-circuit fuses (covered under CSA C22.2 No. 4248.1) and fuses for AC-only applications.
Technical Requirements
Electrical Performance
The standard defines strict requirements for DC voltage rating, time-current characteristics, and breaking capacity. Fuses must interrupt overcurrents at the maximum rated voltage and under specified fault conditions. To ensure reliable operation in PV systems, where fault currents may be low and long-duration, the fuses must exhibit appropriate melting time versus current curves. The table below summarises key electrical parameters for typical supplementary fuses in this standard.
| Parameter | Requirement |
|---|---|
| Rated DC voltage | Up to 1,000 V DC |
| Rated current range | 1 A – 250 A |
| Breaking capacity | ≥ 10 kA (typically 50 kA for high-rupture-capacity types) |
| Overload test | 1.45 × Ir for 1 hour (melting must occur) |
| Time-current characteristic | gPV (full-range) or aPV (partial-range) per manufacturer data |
| Power dissipation | Limited to avoid excessive heating in enclosed fuse holders |
| Insulation resistance | ≥ 5 MΩ (after damp heat test) |
Environmental and Mechanical Tests
Fuses must pass a series of environmental tests reflecting PV installation conditions: dry heat, damp heat cyclic, salt mist, and ultraviolet (UV) exposure for outdoor-rated fuse holders. Mechanical tests verify terminal torque strength, vibration resistance, and secure mounting. The fuse-link marking must be indelible and include rated DC voltage, rated current, breaking capacity symbol, manufacturer logo, and the standard reference.
Tip: Always verify that the fuse-link is marked with both DC voltage and the designation “gPV” or “aPV.” Fuses lacking these markings may not be certified to CSA C22.2 No. 4248.6-07.
Testing and Compliance
Type Tests
Certification to CSA C22.2 No. 4248.6-07 requires successful completion of type tests including: breaking capacity at maximum rated voltage, overload endurance, temperature rise, dielectric withstand, and environmental conditioning. For PV-specific requirements, additional tests simulate reverse current flow caused by string faults and verify that the fuse does not degrade under continuous DC load.
Routine Tests
Each production unit must undergo routine tests: visual inspection, marking verification, and electrical continuity check. Random sampling may be used for resistance and power dissipation control. The manufacturer must maintain a quality management system (e.g., ISO 9001) and submit to periodic factory audits by a certification body such as CSA, UL, or Intertek.
Warning: Using a fuse that is not certified to this standard in a Canadian PV installation may violate the Canadian Electrical Code (CSA C22.1) and void warranties.
Implementation and Compliance Notes
System Design Considerations
When applying CSA C22.2 No. 4248.6-07 fuses, designers must account for module short-circuit current, ambient temperature derating, conductor ampacity, and maximum system voltage. The standard requires that the fuse breaking capacity be at least the prospective short-circuit current at the point of installation. In larger arrays, fuses with 50 kA breaking capacity are recommended. Fuse holders must be chosen with compatible DC ratings and suitable ingress protection (IP) for the environment.
Compliance benefit: Certified fuses provide consistent protection, reduce fire risk, and ensure compatibility with downstream equipment such as inverters and disconnects.
Common mistake: Installing AC-rated fuses in DC PV circuits. AC fuses may not extinguish the DC arc, leading to sustained arcing and equipment damage. Always use DC-rated supplementary fuses per CSA C22.2 No. 4248.6-07.
Frequently Asked Questions
Q: What is the difference between supplementary fuses (4248.6) and branch-circuit fuses (4248.1)?
A: Supplementary fuses are intended for use after a branch-circuit overcurrent device (e.g., in a PV combiner box) and protect individual strings. They have lower interrupting ratings (up to 50 kA) and are tested specific to DC PV conditions. Branch-circuit fuses are for main feeders and can have higher interrupting ratings (e.g., 200 kA) and AC/DC dual ratings.
A: Supplementary fuses are intended for use after a branch-circuit overcurrent device (e.g., in a PV combiner box) and protect individual strings. They have lower interrupting ratings (up to 50 kA) and are tested specific to DC PV conditions. Branch-circuit fuses are for main feeders and can have higher interrupting ratings (e.g., 200 kA) and AC/DC dual ratings.
Q: Can I use a 1,000 V AC fuse in a 1,000 V DC PV system?
A: No. AC fuses are not tested for DC arc extinction, especially under low overcurrent conditions. Using them may cause fire or explosion. Always select a fuse explicitly marked for the applicable DC voltage and compliant with CSA C22.2 No. 4248.6-07.
A: No. AC fuses are not tested for DC arc extinction, especially under low overcurrent conditions. Using them may cause fire or explosion. Always select a fuse explicitly marked for the applicable DC voltage and compliant with CSA C22.2 No. 4248.6-07.
Q: Is certification mandatory for PV fuses sold in Canada?
A: Yes. The Canadian Electrical Code (CSA C22.1) mandates that overcurrent protective devices in PV systems be certified to the appropriate CSA C22.2 standard, including No. 4248.6-07 for supplementary fuses. Provincial authorities typically enforce this requirement.
A: Yes. The Canadian Electrical Code (CSA C22.1) mandates that overcurrent protective devices in PV systems be certified to the appropriate CSA C22.2 standard, including No. 4248.6-07 for supplementary fuses. Provincial authorities typically enforce this requirement.
Q: How often is the standard updated?
A: CSA standards are periodically reaffirmed, revised, or withdrawn. The 4248.6 standard was originally published in 2007 and reaffirmed in 2017. Users should check the latest edition and any applicable amendments on the CSA Group website.
A: CSA standards are periodically reaffirmed, revised, or withdrawn. The 4248.6 standard was originally published in 2007 and reaffirmed in 2017. Users should check the latest edition and any applicable amendments on the CSA Group website.
Article prepared for general informational purposes and does not replace official standard texts. Always consult the complete CSA C22.2 No. 4248.6-07 document and local regulatory authorities for compliance.
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