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CSA C22.2 No. 4248.5-07 (2016): Standard for Class G Fuses – Technical Overview and Compliance
Understanding the Requirements for Class G Supplementary Fuses under the Canadian Electrical Code
Scope and Application
CSA C22.2 No. 4248.5-07 (2016) is the harmonized Canadian standard for Class G fuses, which are supplementary fuses intended for use in accordance with the Canadian Electrical Code (CE Code). Part of the CSA 4248 series on fuses and fuseholders, this standard specifically covers Class G fuses rated up to 600 V ac and 60 A. These fuses are designed for branch circuit protection or as supplementary overcurrent protection in equipment where space is limited. The standard was originally published in 2007 and reaffirmed in 2016, confirming its continued relevance.
Class G fuses are characterized by their compact dimensions, high interrupting capacity, and rejection features that prevent improper substitution. They are typically used in lighting, HVAC, and industrial control panels. This standard is harmonized with UL 4248-5, facilitating acceptance in both Canadian and US markets.
| Parameter | Class G Fuse Ratings (CSA C22.2 No. 4248.5) |
|---|---|
| Voltage (ac) | Up to 600 V |
| Current range | 1 – 60 A |
| Interrupting rating | 100 kA (typical, dependent on rating) |
| Fuse class | G (rejection type, midget tubular) |
| Applicable base standard | CSA C22.2 No. 4248.1 (General Requirements) |
Technical Requirements
Construction and Dimensions
The standard specifies the mechanical and electrical construction of Class G fuses, including rejection features that prevent installation of fuses with higher current ratings into lower-rated fuseholders. Dimensional requirements ensure interchangeability among compliant products, with defined barrel diameters and lengths for each current rating. All metallic parts must resist corrosion, and fuse bodies must meet flame retardance and dielectric strength tests.
Electrical Performance
Key requirements include temperature rise limits during rated current flow, overload endurance at 35% above rated current, and interrupting capacity tests at rated voltage. For short-circuit testing, each fuse must interrupt faults up to its marked interrupting rating, typically 100 kA rms symmetrical. Time-current characteristics are specified to coordinate with upstream protective devices and to provide selective coordination where required.
Marking and Instructions
Every fuse must be permanently marked with the manufacturer’s name or trademark, catalogue number, rated voltage, rated current, and interrupting rating. Additionally, the fuse must indicate the CSA certification mark. Accompanying documentation must include installation instructions and warnings about replacing only with fuses of identical ratings and type.
Tip: Always verify that the interrupting rating of a Class G fuse is suitable for the available fault current at the point of installation. Using a fuse with an insufficient interrupting rating can result in catastrophic failure during a short circuit.
Warning: Class G fuses are current-limiting devices. Replacing a fuse with a non-current-limiting type can void equipment protection and cause arc flash hazards. Only Class G fuses that meet CSA C22.2 No. 4248.5 should be used in designated circuits.
Implementation and Testing
To demonstrate compliance with CSA C22.2 No. 4248.5-07 (2016), manufacturers conduct a series of type tests on representative fuse samples. These tests are performed in CSA-accredited laboratories and include:
- Dielectric voltage-withstand test – Verifies insulation between live parts and mounting surface.
- Temperature rise test – At rated current, temperature rise must not exceed 65 °C above ambient at any point.
- Overload test – The fuse must carry 135% of rated current for one hour without opening, then interrupt a specified overcurrent.
- Short-circuit test – Up to the fuse’s marked interrupting rating, usually performed at power factors representative of utility systems.
- Endurance test – For fuse types intended for repeated opening, a number of operations at rated current and voltage.
Manufacturers must also implement a factory production control program to ensure consistent quality and performance. The standard references CSA C22.2 No. 4248.1 for general test methods and conditions.
Success: Harmonization of CSA C22.2 No. 4248.5 with UL 4248-5 simplifies certification for products sold in both Canada and the United States. A single test program can satisfy both standards, reducing time to market.
Compliance and Certification Notes
Certification of Class G fuses to CSA C22.2 No. 4248.5-07 (2016) is typically performed by recognized certification bodies such as CSA Group (the standard’s developer) or other accredited agencies. Acceptance under the Canadian Electrical Code requires that fuses bear a CSA certification mark or an equivalent accredited mark recognized by the provincial authority.
It is important to note that the 2016 reaffirmation did not introduce technical changes; it confirmed that the 2007 edition remains current. Installers and specifiers should always use the latest edition of the standard and check for any amendments issued by CSA Group. Field-installed Class G fuses must be applied within their marked ratings and installed in compatible fuseholders that also meet the applicable CSA standard (e.g., CSA C22.2 No. 4248.15 for Class G fuseholders).
Danger: Use of non-certified or counterfeit Class G fuses can lead to equipment damage, fire, and serious injury. Always source from reputable manufacturers and verify the certification mark. Never replace a fuse with a different class or higher rating than originally specified.
Frequently Asked Questions
Q: What is the difference between a Class G fuse and other supplementary fuses like Class CC or Class J?
A: Class G fuses have specific dimensional and rejection features that differ from other classes. They are designed for applications up to 600 V and 60 A with a high interrupting rating. Class CC fuses are smaller (13/32″ diameter) and typically used for control circuits, while Class J fuses have higher current ratings and different physical dimensions. The choice depends on voltage, current, interrupting rating, and the fuseholder design.
A: Class G fuses have specific dimensional and rejection features that differ from other classes. They are designed for applications up to 600 V and 60 A with a high interrupting rating. Class CC fuses are smaller (13/32″ diameter) and typically used for control circuits, while Class J fuses have higher current ratings and different physical dimensions. The choice depends on voltage, current, interrupting rating, and the fuseholder design.
Q: Does CSA C22.2 No. 4248.5-07 (2016) apply to both AC and DC applications?
A: The standard mainly covers AC applications (50/60 Hz). For DC ratings, additional testing per the general standard (CSA C22.2 No. 4248.1) may be required. The fuse’s marking must specify if it is suitable for DC and state the rated DC voltage.
A: The standard mainly covers AC applications (50/60 Hz). For DC ratings, additional testing per the general standard (CSA C22.2 No. 4248.1) may be required. The fuse’s marking must specify if it is suitable for DC and state the rated DC voltage.
Q: Can Class G fuses be used on circuits with high inrush currents, such as motor starters?
A: Class G fuses are time-delay (slow-blow) types with relatively high inrush tolerance, making them suitable for inductive loads like motors. However, coordination with the motor overload relay must be verified. The fuse must have adequate time-current characteristics to avoid nuisance opening during motor starting.
A: Class G fuses are time-delay (slow-blow) types with relatively high inrush tolerance, making them suitable for inductive loads like motors. However, coordination with the motor overload relay must be verified. The fuse must have adequate time-current characteristics to avoid nuisance opening during motor starting.
Q: How should I store and handle Class G fuses to maintain their performance?
A: Store fuses in a dry, clean environment away from corrosive substances and extreme temperatures. Do not drop or subject them to mechanical shock. Always handle by the body; avoid touching the end caps to prevent contamination that could affect electrical connection.
A: Store fuses in a dry, clean environment away from corrosive substances and extreme temperatures. Do not drop or subject them to mechanical shock. Always handle by the body; avoid touching the end caps to prevent contamination that could affect electrical connection.
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