CSA C22.2 No. 45.1-07 (2017): Safety Requirements for Low-Voltage Transformers

CSA C22.2 No. 45.1-07 (2017) is a national standard of Canada developed under the Canadian Standards Association (CSA) that specifies safety requirements for low-voltage dry-type transformers rated 600 V or less. This standard, reaffirmed in 2017, is widely referenced by the Canadian Electrical Code (CE Code) and serves as the benchmark for transformer manufacturers, importers, and installers who seek compliance with Canadian safety regulations.

Scope and Application

CSA C22.2 No. 45.1-07 applies to single-phase and polyphase low-voltage dry-type transformers intended for use in non-hazardous and some hazardous locations in accordance with the CE Code. The standard covers:

General-purpose power transformers
Class 2 and Class 3 power supplies
Ferroresonant and electronic step-down transformers
Transformers provided with encapsulated or open-winding constructions

Excluded from the scope are liquid-filled transformers, instrument transformers, and transformers intended for use in explosion-proof enclosures unless specifically covered by complementary standards.

Design Insight: When designing transformers for CSA certification, note that the standard permits either encapsulated or open-winding construction, but each imposes unique thermal and clearance requirements. Encapsulated designs often require additional dielectric testing due to the stress on potting materials.

Technical Requirements

The standard establishes a comprehensive set of safety and performance parameters. Key requirements include:

Electrical Insulation and Dielectric Strength

Transformers must withstand a dielectric voltage withstand test (high-potential test) at twice the rated voltage plus 1000 V, applied between primary and secondary windings and between windings and core. The minimum test voltage is 1500 V for circuits rated 250 V or less.

Temperature Rise Limits

Temperature rise above ambient is limited by the insulation class, as shown in the table below:

Insulation Class	Maximum Temperature Rise (by resistance)
Class A (105°C)	55°C
Class B (130°C)	80°C
Class F (155°C)	105°C
Class H (180°C)	125°C

Short-Circuit Withstand

Transformers rated up to 10 kVA must withstand a short-circuit test of 25 times rated current for a duration of 2 seconds without exceeding a specified temperature limit. Larger transformers are tested based on design and application conditions.

Marking and Documentation

Each transformer must be permanently marked with the manufacturer’s name, model, ratings, compliance symbol, and safety warnings. The standard requires specific caution statements if the transformer is not suitable for Class 2 or Class 3 circuits.

Warning: Deviating from the prescribed short-circuit test parameters may void certification. Always design for the worst-case fault condition, including line voltage variations of ±10%.

Implementation Highlights

Practical adoption of CSA C22.2 No. 45.1-07 involves several engineering considerations:

Thermal Management: Use of appropriate winding materials and heat sinks to maintain temperature rise within limits.
Clearance and Creepage: Minimum distances specified in the standard (based on working voltage and pollution degree) must be observed.
Input/Output Separation: Physical spacing between primary and secondary terminals to prevent accidental bridging.
Overcurrent Protection: The standard assumes the transformer will be installed with branch circuit overcurrent protection sized per the CE Code.

Certification Success: Many manufacturers find that designing to the 2017 reaffirmed version aligns well with the latest UL 5085-3 requirements for North American harmonization. Early engagement with a CSA testing laboratory can identify gaps before formal testing.

Compliance and Certification Notes

To demonstrate compliance with CSA C22.2 No. 45.1-07, manufacturers must submit samples to an accredited certification body (e.g., CSA, Intertek, UL). The process includes:

Construction review and documentation check
Type testing (dielectric, temperature rise, short-circuit)
Factory production line tests (routine hi-pot, continuity)
Follow-up inspection and routine audits

Marking the product with the CSA monogram or a recognized certification mark is mandatory for sale in Canada under the jurisdiction of the CE Code. Reaffirmation in 2017 confirmed that no substantive changes were needed, so the 2007 edition remains current.

Danger: Operation of transformers not certified to CSA C22.2 No. 45.1-07 in Canadian installations can result in severe safety hazards, voided insurance, and regulatory penalties. Always verify that the product bears a valid Canadian certification mark.

For retrofits or field modifications, any change that affects the electrical or thermal performance—such as rewind with different wire gauge—typically requires recertification. The standard does not allow extended overloading beyond the nameplate ratings under normal service conditions.

Q: What types of transformers fall under CSA C22.2 No. 45.1-07?
A: The standard covers dry-type low-voltage transformers (≤600 V) used for general power, Class 2/Class 3 supplies, and similar applications. It excludes liquid-filled, instrument, and specialty transformers covered by other CSA standards.

Q: Is the 2007 edition still valid given its reaffirmation in 2017?
A: Yes, the standard was reaffirmed without technical changes in 2017, meaning it is still the current edition. Users should always check the CSA website for any amendments or the latest revision status.

Q: How does this standard relate to the Canadian Electrical Code?
A: CSA C22.2 No. 45.1-07 is referenced by the CE Code (CSA C22.1) for the installation of low-voltage dry-type transformers. Compliance with this product standard is typically required to meet Code requirements for safety.

Q: Can I use a transformer certified to UL 5085-3 in Canada?
A: UL 5085-3 is similar but not identical. The CSA mark is mandatory in Canada. Some certification bodies offer combined testing to both standards, reducing duplication. Check with your certification body for harmonized options.

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