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CSA C22.2 No. 248.11-11 (2016): Low-Voltage Fuses – Part 11: Plug Fuses – Technical Requirements and Compliance
Harmonized Standard for Edison-base and Type S Plug Fuses in Residential and Commercial Overcurrent Protection
Plug fuses remain a widely used form of branch-circuit overcurrent protection in existing residential and light commercial installations throughout Canada. The standard CSA C22.2 No. 248.11-11 (2016), titled Low-voltage fuses – Part 11: Plug fuses, defines the construction, performance, and marking requirements for plug fuses intended to be installed in accordance with the Canadian Electrical Code (CE Code). This article provides a technical overview of the standard, covering its scope, critical design and testing criteria, implementation considerations, and compliance pathways.
Scope and Application
CSA C22.2 No. 248.11-11 (2016) applies to plug fuses having nominal voltage ratings of 125 V ac or less and current ratings up to 30 A. The standard covers both Edison-base (parallel-thread lens) and Type S (asymmetric tamper-resistant) plug fuses. It also addresses plug fuseholders.
The standard is harmonized with the bi-national and tri-national low-voltage fuse family, which includes UL 248-11 (United States) and NMX-J-118/248-11-ANCE (Mexico). Compliance with this CSA standard is mandated by provincial electrical safety authorities and is a prerequisite for certification and field acceptance of plug fuses under the CE Code.
Technical Requirements
Construction and Materials
Plug fuses must be constructed with robust, arc-resistant enclosures (typically glass, ceramic, or melamine) and conductive elements of copper, zinc, or alloys that provide predictable time-current characteristics. Type S fuses incorporate mechanical rejection features that physically prevent a higher-amperage fuse from being installed in a lower-rated circuit. These features are mandatory to reduce the risk of overfusing.
Fuse terminals must accept standard Edison-base sockets for replacement compatibility. For Type S fuses, an adapter is supplied that screws into the existing Edison-base socket and accepts only Type S fuses of the same or lower current rating. The adapter is not removable once installed.
Ratings and Markings
Each fuse must be durably marked with the rated voltage, rated current, interrupting rating (if optional), manufacturer’s identification, catalogue number, and the certification mark of an accredited body (e.g., CSA, cULus). Standard current ratings for Edison-base plug fuses are 15, 20, and 30 A; Type S plug fuses are offered additionally in 20, 25, and 30 A types.
Tests and Performance Criteria
The standard prescribes a series of type tests to verify electrical, thermal, and mechanical integrity. These include:
- Temperature rise test – At rated current, the temperature rise of the fuse terminals and body must not exceed 50°C above ambient.
- Overload test – The fuse must carry 135% of its rated current for one hour without opening or exhibiting damage.
- Endurance test (Type S only) – After 50 manual insertion/withdrawal cycles at rated voltage and current, the rejection feature must still function.
- Short-circuit tests – Interrupting ratings of 10 kA (standard) or 20 kA (optional) are verified by controlled fault tests.
| Test | Condition | Acceptance Criterion |
|---|---|---|
| Temperature rise | 100% rated current, steady-state | ΔT ≤ 50 °C |
| Overload | 135% rated current, 1 hour | No fuse opening, no damage |
| Endurance (Type S) | 50 operations at rated load | Rejection feature remains effective |
| Short-circuit | Rated interrupting current (10 or 20 kA) | Arc containment, no rupture |
Implementation and Installation Considerations
When replacing plug fuses in existing installations, the current rating must never exceed the ampacity of the branch-circuit conductors. Edison-base fuseholders are not required to have rejection features, but many jurisdictions require that new panels or service upgrades be equipped with Type S fuseholders or circuit breakers.
For older homes with Edison-base fuse panels, Type S adapters provide tamper-resistant protection. Once installed, the adapter normally cannot be removed, ensuring that only Type S fuses of the correct rating are used.
Warning: Never install a plug fuse with a higher current rating than the circuit was designed for. Overfusing is a leading cause of electrical fires. Use only Type S systems to enforce correct fuse sizing.
Compliance and Certification
Plug fuses sold in Canada must be certified to CSA C22.2 No. 248.11-11 by a recognized third-party certification body such as CSA Group, Underwriters Laboratories (UL), or Intertek (ETL). Certification demonstrates that the product has passed all required type tests and factory production inspections. The standard is updated periodically, and manufacturers must maintain ongoing compliance through audits.
Certification mark visible on the product (e.g., CSA Mark) confirms compliance with CSA C22.2 No. 248.11-11 (2016) and acceptance under the Canadian Electrical Code.
Q: What is the difference between Edison-base and Type S plug fuses?
A: Edison-base fuses have a standard screw base and accept any plug fuse of the same physical size. Type S fuses incorporate a mechanical keying system that prevents a fuse with a higher current rating from being inserted into a lower-rated socket. Type S adapters are available for retrofitting Edison-base panels.
A: Edison-base fuses have a standard screw base and accept any plug fuse of the same physical size. Type S fuses incorporate a mechanical keying system that prevents a fuse with a higher current rating from being inserted into a lower-rated socket. Type S adapters are available for retrofitting Edison-base panels.
Q: Can I replace a plug fuse with a circuit breaker?
A: Yes. The CE Code permits replacement of an existing fuse panel with a circuit breaker panel provided the new panel complies with current Code requirements. Alternatively, plug-in circuit breakers that fit into Edison-base sockets are available, but they must be listed for that purpose (e.g., UL/CSA-listed).
A: Yes. The CE Code permits replacement of an existing fuse panel with a circuit breaker panel provided the new panel complies with current Code requirements. Alternatively, plug-in circuit breakers that fit into Edison-base sockets are available, but they must be listed for that purpose (e.g., UL/CSA-listed).
Q: Are Type S adapters reusable after removal?
A: No. Type S adapters are designed to be permanent; if removed, the rejection feature is typically destroyed to prevent reuse. This ensures that the tamper-resistant system remains effective after initial installation.
A: No. Type S adapters are designed to be permanent; if removed, the rejection feature is typically destroyed to prevent reuse. This ensures that the tamper-resistant system remains effective after initial installation.
Technical Reference: CSA C22.2 No. 248.11-11 (2016) – Low-voltage fuses – Part 11: Plug fuses. This article provides general information and does not substitute for reading the official standard. Compliance verification must be conducted by a recognized certification body.
Published 2026