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CSA C22.2 No. 25-17: Enclosures for Use in Class I, Division 2 Hazardous Locations – Technical Overview and Compliance Guide
Understanding the Requirements for Electrical Equipment Enclosures in Class I, Division 2 Areas Under the Canadian Electrical Code
Scope and Application
CSA C22.2 No. 25-17, titled Enclosures for Use in Class I, Division 2 Hazardous Locations, is a key Canadian standard developed under the Canadian Electrical Code (CE Code) framework. It specifies the construction, testing, and marking requirements for enclosures intended to contain electrical equipment in Class I, Division 2 locations where flammable gases or vapors are present only under abnormal conditions. The standard applies to enclosures for equipment such as terminals, control devices, and junction boxes that are not intended to be opened while energized and do not contain arcing or sparking components unless specifically permitted by the standard.
The standard revision from 2017 incorporates updated testing methods, clarifications on enclosure materials, and alignment with the latest edition of the CE Code. It is intended for use by manufacturers, certifying bodies, and engineers specifying hazardous location equipment in Canada.
Important: This standard does not cover enclosures for Class I, Division 1 locations (where ignitable concentrations exist under normal operation). For Division 1, refer to CSA C22.2 No. 30 (explosion-proof enclosures) or other applicable standards.
Key Technical Requirements
Construction and Materials
Enclosures must be constructed from materials that can withstand the mechanical, thermal, and corrosive stresses expected in the intended service environment. The standard requires that enclosures be non-combustible or have a limited-combustibility rating. Commonly used materials include cast iron, cast aluminum, stainless steel, and fiberglass-reinforced polyester. Enclosures must be designed to prevent the entrance of combustible dust, fibers, or flyings if installed in mixed hazardous locations, although the primary focus is gas/vapor atmospheres.
Temperature Classification
The maximum surface temperature of the enclosure under rated load and abnormal conditions must not exceed the ignition temperature of the surrounding gas or vapor. CSA C22.2 No. 25-17 adopts the temperature classification system consistent with the CE Code and international practice. Table 1 summarizes the temperature classes and corresponding maximum surface temperatures.
| Temperature Class | Maximum Surface Temperature (°C) | Typical Gas/Vapor Examples |
|---|---|---|
| T1 | 450 | Acetone, ammonia, benzene |
| T2 | 300 | Ethyl alcohol, ethylene, hydrogen sulfide |
| T3 | 200 | Gasoline, hexane, naphtha |
| T4 | 135 | Diethyl ether, ethylene oxide |
| T5 | 100 | Carbon disulfide |
| T6 | 85 | Acetaldehyde, ethyl nitrite |
Sealing and Gaskets
Enclosures must be provided with a means of sealing to prevent the ingress of gases and vapors under normal and abnormal conditions. Gaskets or O-rings must be made of materials resistant to the anticipated chemical exposure. The standard specifies aging and compression set tests to ensure long-term seal integrity.
Marking and Documentation
Each enclosure must be permanently marked with the manufacturer’s name, catalog number, temperature class, Class I, Division 2 designation, and the standard number CSA C22.2 No. 25-17. Markings must be legible and durable. Installation instructions must include torque values for cover bolts and any special precautions for field modifications.
Implementation Highlights and Compliance Notes
Testing Requirements
CSA C22.2 No. 25-17 requires a series of type tests including:
- Hydrostatic test: Enclosures must withstand a pressure of 1.5 times the rated pressure without rupture.
- Impact test: A steel ball impact test (typically 7 J) to verify mechanical strength.
- Temperature test: Under full load and worst-case internal fault conditions, the maximum external temperature must not exceed the temperature class limit.
- Gasket aging test: Accelerated aging at elevated temperature for 168 hours followed by compression set measurement.
Manufacturers must implement a quality control plan to ensure ongoing compliance during production.
Tip: When specifying enclosures for outdoor installation, ensure they are also rated for environmental conditions (corrosion, UV exposure). CSA C22.2 No. 25-17 does not replace the need for NEMA or IP ingress protection ratings.
Field Installation Considerations
Compliance with the standard is mandatory for new installations in Canadian jurisdictions adopting the CE Code. Installers must ensure that:
- Enclosure openings are properly sealed to maintain the integrity of the Division 2 boundary,
- Conduit entries use approved seals, and
- Equipment inside the enclosure does not exceed the temperature class rating of the enclosure.
Warning: Opening an enclosure in a Division 2 location while the circuit is energized can create an ignition hazard. All maintenance must follow the site-specific hazardous area management plan and permit-to-work procedures.
Comparison with Related Standards
CSA C22.2 No. 25-17 is harmonized in many respects with UL 698 (Industrial Control Equipment for Use in Hazardous Locations) and CSA C22.2 No. 213 (Non-incendive Electrical Equipment). However, it specifically addresses enclosures as a component. For complete equipment assemblies, other standards such as CSA C22.2 No. 1010.1 (for measurement equipment) may also apply. Manufacturers should consult the product standard relevant to the installed equipment.
Compliance Success: A well-designed enclosure meeting CSA C22.2 No. 25-17 can provide years of safe service in Class I, Division 2 environments. Routine inspection of seals and gaskets is recommended to maintain the safety integrity.
Frequently Asked Questions
Q: What is the difference between Class I, Division 2 and Class I, Division 1 as related to CSA C22.2 No. 25-17?
A: Division 1 locations have ignitable concentrations of gas or vapor under normal operating conditions, while Division 2 locations have such concentrations only under abnormal conditions such as a leak or equipment failure. CSA C22.2 No. 25-17 is specifically written for enclosures in Division 2 locations. Division 1 enclosures must meet more stringent requirements (e.g., explosion-proof design per CSA C22.2 No. 30).
A: Division 1 locations have ignitable concentrations of gas or vapor under normal operating conditions, while Division 2 locations have such concentrations only under abnormal conditions such as a leak or equipment failure. CSA C22.2 No. 25-17 is specifically written for enclosures in Division 2 locations. Division 1 enclosures must meet more stringent requirements (e.g., explosion-proof design per CSA C22.2 No. 30).
Q: Can an enclosure certified under CSA C22.2 No. 25-17 be used in a Class I, Division 1 area?
A: No. The standard does not provide the level of protection required for Division 1. Using a Division 2 enclosure in a Division 1 area would not comply with the CE Code and would create a safety hazard.
A: No. The standard does not provide the level of protection required for Division 1. Using a Division 2 enclosure in a Division 1 area would not comply with the CE Code and would create a safety hazard.
Q: Does CSA C22.2 No. 25-17 require third-party certification?
A: While the standard itself is a baseline for design and testing, Canadian authorities having jurisdiction (AHJs) typically require that enclosures be certified by an accredited certification body (e.g., CSA Group, UL, Intertek) to demonstrate compliance with the standard.
A: While the standard itself is a baseline for design and testing, Canadian authorities having jurisdiction (AHJs) typically require that enclosures be certified by an accredited certification body (e.g., CSA Group, UL, Intertek) to demonstrate compliance with the standard.
Q: What temperature class should I specify for an enclosure installed near a flammable liquid handling area?
A: Determine the auto-ignition temperature of the most likely flammable gas or vapor in the area. Select a temperature class whose maximum surface temperature (see Table 1) is less than that ignition temperature. Common selections for gasoline service are T3 (200 °C) or T4 (135 °C) depending on the specific substance.
A: Determine the auto-ignition temperature of the most likely flammable gas or vapor in the area. Select a temperature class whose maximum surface temperature (see Table 1) is less than that ignition temperature. Common selections for gasoline service are T3 (200 °C) or T4 (135 °C) depending on the specific substance.