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CSA C22.2 No. 4248.9-07 (R2016): Performance Requirements for Fuseholders for Class K, J, R, T and CC Fuses
A Comprehensive Guide to the Canadian Standard for Fuseholder Safety and Performance
CSA C22.2 No. 4248.9-07 (R2016) is a key Canadian standard that establishes performance and safety requirements for fuseholders designed to accept specific classes of cartridge fuses. As part of the harmonized CSA C22.2 No. 4248 series, this standard aligns closely with UL 4248-9 while incorporating Canadian electrical code (CEC) deviations and national requirements. This article provides a technical overview of the standard’s scope, essential technical criteria, implementation guidance, and compliance considerations for engineers, specifiers, and manufacturers.
Scope and Application
CSA C22.2 No. 4248.9-07 (R2016) applies to fuseholders intended for use on alternating-current (AC) circuits rated up to 600 V and direct-current (DC) circuits up to 300 V. The standard covers fuseholders that accept the following fuse classes:
- Class K – Non-renewable, non-rejection fuses (K-1, K-5, K-9)
- Class J – Current-limiting, rejection-type fuses (J-600, J-300)
- Class R – Rejection-type fuses (R-600, R-300)
- Class T – Current-limiting, rejection-type fuses (300 V or 600 V ratings)
- Class CC – Small-dimension, rejection-type fuses (600 V, 30 A max)
Fuseholders covered by this standard may be open (panel-mount) or enclosed in insulating material, and include those with supplemental devices such as indicating lights, switches, or disconnects. The standard also addresses fuseholders that are factory-installed in equipment as well as those intended for field installation.
Excluded from scope are fuseholders for non-current-limiting fuses (e.g., Class H) and industrial high-voltage fuses. Plug-type or Edison-base holders are also not covered.
Tip: When specifying holders for Class J, R, T, or CC fuse classes, always verify that the holder incorporates the mandatory rejection features required by CSA C22.2 No. 4248.9. This ensures that only the intended fuse class can be inserted, preventing unsafe overfusing or substitution.
Technical Requirements
General Construction and Rejection Features
Fuseholders for rejection-type fuses (Classes J, R, T, and CC) must incorporate physical features that prevent insertion of non-rejection fuses (e.g., Class H). For Class R holders, this typically involves a rejection slot or groove in the barrel or blade; for Class T holders, dimensional restrictions differ for 300 V and 600 V versions. Class CC holders use a special “D” or “B” configuration pin arrangement. The standard details precise dimensional checks and gauging procedures for each class.
Temperature Rise Limits
Under continuous current conditions, all current-carrying parts and accessible surfaces must not exceed specified temperature rises above ambient (typically 40 °C). Table 1 summarises the maximum allowable temperature rises:
| Component / Material | Maximum Temperature Rise (K) | Test Current |
|---|---|---|
| Copper terminals (screw-type) | 45 | 100 % rated current |
| Other metal terminals (aluminum, brass) | 50 | 100 % rated current |
| Enclosure metal parts (accessible) | 40 | 100 % rated current |
| Internal current-carrying parts (copper) | 55 | 100 % rated current |
| Insulating material (enclosures) | 60 | 100 % rated current |
Table 1 – Maximum permissible temperature rise measured at an ambient of 40 °C; values based on typical requirements of CSA C22.2 No. 4248.9 and UL 4248-9.
Dielectric Voltage-Withstand
Live parts must withstand 1500 V AC (or 2100 V DC) for 1 minute between pole-to-pole and between live parts and non-current-carrying metal parts. For enclosed holders, a 1500 V test is applied between live parts and the enclosure. Leakage current must not exceed 0.5 mA.
Short-Circuit Performance
Fuseholders must be capable of withstanding the maximum prospective short-circuit current available at the point of installation without fire, arcing to ground, or ejection of parts. The standard requires testing at rated voltage and at fault currents up to 200 kA rms symmetric for Class J holders, and 100 kA for Class K, R, T, and CC holders (depending on current rating). A fuse of appropriate class and size must be installed in the holder during the short-circuit test, and after the test the holder must be safe for continued service.
Warning: Non-rejection holders (Class K) must not be used in circuits that require a rejection-type holder, even if the fuse itself has rejection features. The CEC Part I mandates rejection holders for branch-circuit overcurrent protection in many applications.
Mechanical Endurance and Overload
Fuseholders intended for frequent operation under load are tested for 2000 cycles of insertion/removal at 115 % of rated voltage and 150 % of rated current. After endurance testing, the holder must show no damage that impairs its electrical or mechanical function, and temperature rise must remain within limits.
Implementation Highlights
Manufacturers seeking CSA certification should note the following critical aspects during product development:
- Material Selection: All current-carrying parts should be copper, brass, or equivalent, with platings that resist corrosion. Terminal screws must meet CSA C22.2 No. 0.4 requirements for binding head screws.
- Rejection Feature Design: Precise dimensional control of rejection slots, grooves, and pin configurations is essential. Use of dedicated gauges as defined in Annex A of the standard will ensure interchangeability with compliant fuses.
- Wire Range and Torque: Terminals must accommodate the wire sizes required for the fuseholder’s current rating (e.g., 14 AWG to 2 AWG for 30 A to 200 A). Torque values for terminal screws are specified in Table 5 of the standard (e.g., 2.5 Nm for 8 AWG).
- Environmental Conditioning: The standard requires humidity, temperature cycling, and UV resistance tests (if exposed in outdoor enclosures).
- Marking and Instructions: Permanent marking must include rated voltage, rated current, fuse class, short-circuit current rating, and the CSA certification mark. Installation instructions must reference the CEC and specify torque values if different from Table 5.
Success: CSA certification of a fuseholder to C22.2 No. 4248.9-07 (R2016) is recognized by all provincial and territorial electrical authorities in Canada, facilitating market access across the country.
Compliance Notes
Adherence to CSA C22.2 No. 4248.9-07 (R2016) is mandatory for fuseholders intended for use in Canada under the authority of the CEC Part I. Key compliance points:
- Harmonization with UL 4248-9: The Canadian standard is technically identical to UL 4248-9, but includes Canadian deviations (e.g., additional requirements for grounded enclosures, mandatory marking of Class R and T holders with the word “REJECTION”, and more stringent wire binding tests).
- Factory Follow-Up: Each certified product group requires periodic CSA follow-up inspections to verify ongoing compliance; changes in materials or suppliers may necessitate re-evaluation.
- Field-Installed vs. Factory-Installed: While the standard covers both, factory-installed holders must be tested as part of the end-use equipment (e.g., panelboard). Field-installed holders must include clear installation instructions and torque markings.
- Interrupting Capacity Marking: The short-circuit current rating (SCCR) of the fuseholder must be marked on the product and in the installation instructions. When the SCCR differs from the fuse SCCR, the lower value must be used for the combination.
Danger: Using a fuseholder that has not been short-circuit tested with the specific fuse class can lead to catastrophic failure during a fault. Always confirm that the holder – fuse combination is listed for the available fault current.
FAQs
Q: What fuse classes are covered by CSA C22.2 No. 4248.9-07 (R2016)?
A: The standard covers fuseholders for Classes K, J, R, T, and CC cartridge fuses. These include both non-rejection (K) and rejection-type (J, R, T, CC) configurations, with voltage ratings up to 600 V AC and 300 V DC, and current ratings typically up to 600 A.
A: The standard covers fuseholders for Classes K, J, R, T, and CC cartridge fuses. These include both non-rejection (K) and rejection-type (J, R, T, CC) configurations, with voltage ratings up to 600 V AC and 300 V DC, and current ratings typically up to 600 A.
Q: Is CSA C22.2 No. 4248.9 identical to UL 4248-9?
A: They are harmonised, but CSA C22.2 No. 4248.9 includes Canadian-specific deviations, such as additional grounding requirements, more stringent terminal torque tests, and specific marking obligations for rejection-type holders (e.g., the word “REJECTION” on the product). For compliance in Canada, the Canadian version must be used.
A: They are harmonised, but CSA C22.2 No. 4248.9 includes Canadian-specific deviations, such as additional grounding requirements, more stringent terminal torque tests, and specific marking obligations for rejection-type holders (e.g., the word “REJECTION” on the product). For compliance in Canada, the Canadian version must be used.
Q: Do fuseholders for Class K fuses need rejection features?
A: No. Class K fuses are non-rejection and can be inserted into any corresponding Class K holder. However, the CEC may require rejection-type holders in most branch circuits; in such cases only Class J, R, T, or CC (with rejection) are acceptable. Class K holders are limited to older equipment or specific replacement scenarios.
A: No. Class K fuses are non-rejection and can be inserted into any corresponding Class K holder. However, the CEC may require rejection-type holders in most branch circuits; in such cases only Class J, R, T, or CC (with rejection) are acceptable. Class K holders are limited to older equipment or specific replacement scenarios.
Q: What are the typical short-circuit current ratings for these fuseholders?
A: Depending on the fuse class and current rating, the standard requires testing at up to 200 kA rms symmetric (Class J) or 100 kA (Classes K, R, T, and CC). The marked SCCR of the holder must be at least as high as the available fault current at its installed location.
A: Depending on the fuse class and current rating, the standard requires testing at up to 200 kA rms symmetric (Class J) or 100 kA (Classes K, R, T, and CC). The marked SCCR of the holder must be at least as high as the available fault current at its installed location.
Last revised: 2026. This article is intended for informational purposes and does not substitute for the full text of CSA C22.2 No. 4248.9-07 (R2016). Always consult the latest edition of the standard for complete requirements.