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CSA C22.2 No. 165-17: Temperature Measuring and Limiting Devices – Scope, Requirements, and Compliance
Understanding the Canadian Standard for Temperature Controls in Electrical Applications
CSA C22.2 No. 165-17, part of the Canadian Electrical Code (CE Code) Part II series, establishes the safety and performance requirements for temperature measuring and limiting devices intended for use in electrical equipment. These devices include thermostats, temperature limiters, thermal cutoffs, and temperature sensors that are relied upon to prevent overheating or maintain controlled temperatures in industrial, commercial, and residential applications. This article provides an in-depth review of the standard, focusing on its scope, key technical requirements, practical implementation aspects, and compliance pathways.
1. Scope of CSA C22.2 No. 165-17
The standard applies to temperature measuring and limiting devices that are designed to be installed in accordance with the CE Code, Part I (CSA C22.1). It covers devices rated up to 600 V AC or DC, with a maximum load current limited to the device’s contact rating. The scope includes:
- Temperature-actuated controls that sense and respond to changes in temperature.
- Manual reset and automatic reset temperature limiters.
- Thermal cutoffs (one-shot devices) and thermal fuses.
- Temperature sensors used in control circuits, provided they are part of a complete device assembly.
Devices covered by this standard are intended to be installed in equipment such as heaters, ovens, HVAC systems, water heaters, and similar appliances. The standard also includes requirements for miscellaneous accessories such as mounting brackets, capillary tubing, and adjustment mechanisms.
Important: CSA C22.2 No. 165-17 does not cover temperature-measuring devices used solely for indication (e.g., thermometers without control function) or devices that are integral parts of equipment covered by other specific product standards (e.g., thermostats inside a room air conditioner certified to CSA C22.2 No. 117).
2. Technical Requirements
The standard specifies a comprehensive set of requirements to ensure safe and reliable operation under normal and abnormal conditions. These are categorized into construction, performance, and testing provisions.
2.1 Construction Requirements
- Materials: Enclosures and insulating parts must be made of materials with suitable thermal endurance and resistance to flame propagation. Creepage and clearance distances are specified based on rated voltage and category of use.
- Contacts: Switching contacts must be designed to handle the rated current and voltage, with appropriate gap and material to prevent welding or excessive arcing.
- Temperature sensing elements: Must be robust against mechanical stress and accurately reproduce temperature response curves within specified tolerances.
- Adjustment and calibration: Means for setting or calibrating the operating temperature must be secure and not susceptible to inadvertent tampering.
2.2 Performance and Endurance
Devices must undergo endurance tests simulating their intended life cycle. For temperature limiters, a minimum number of operations (e.g., 100,000 cycles for automatic reset devices, 6,000 cycles for manual reset devices) is required without failure. Temperature measuring devices must maintain accuracy within ±5 °C or ±2% of full scale, whichever is greater, after environmental conditioning.
| Device Type | Endurance Cycles (Min.) | Accuracy Requirement | Overload Test |
|---|---|---|---|
| Automatic reset temperature limiter | 100,000 | ±5 °C / ±2% | 1.5 × rated current, 50 cycles |
| Manual reset temperature limiter | 6,000 | ±5 °C / ±2% | 1.5 × rated current, 50 cycles |
| Thermal cutoff (single-shot) | 1 (operating test) | ±2 °C or ±1% | N/A (short-circuit test applicable) |
| Temperature sensor (control signal) | 100,000 (if cycled) | ±2 °C at calibration point | Dielectric withstand voltage |
Design Tip: When selecting temperature-limiting devices for applications requiring high reliability, choose models with a generous safety margin between the operating temperature and the maximum ambient rating of the enclosure. Pay careful attention to the thermal time constant of the sensor to avoid nuisance tripping.
2.3 Dielectric Strength and Insulation
Insulation between live parts, and between live parts and accessible metal, must withstand a dielectric test at 1000 V + 2 × rated voltage, with a minimum of 1500 V AC for devices rated up to 600 V. Leakage current under normal conditions must not exceed 0.5 mA. For double-insulated devices, additional tests are required.
3. Implementation Highlights
Implementing CSA C22.2 No. 165-17 in product design requires careful planning from the early development phase. Below are practical observations for manufacturers and engineers.
3.1 Device Selection for Specific Applications
Matching the device characteristics to the application reduces compliance risk. For example, in capacitive or inductive load circuits, derating of contacts and additional arc suppression may be necessary. The standard requires devices to be tested with the intended load type, so testing must cover resistive, inductive, and capacitive profiles where applicable.
3.2 Marking and Documentation
Marking requirements are detailed in Clause 6 of the standard. Each device must be permanently marked with:
- Manufacturer’s name or trademark
- Catalogue or model number
- Rated voltage and current
- Temperature rating (set point or range)
- Type of reset (automatic or manual)
- CSA certification mark
- Environmental rating (e.g., –20 °C to +85 °C)
Compliance Benefit: Adherence to CSA C22.2 No. 165-17 simplifies certification to the Canadian Electrical Code and facilitates market acceptance across Canada. It also aligns with occupational health and safety requirements in most provinces.
3.3 Installation Considerations
Installers must follow the instructions provided with the device, particularly regarding mounting orientation, wire size, and separation from heat sources. The standard requires devices to include wiring diagrams or installation instructions that detail correct connections and torque values for terminals. For temperature limiters used in heating equipment, proper sensor placement is critical to ensure accurate sensing and avoid overheating.
4. Compliance and Certification Notes
CSA Group (formerly Canadian Standards Association) is the primary certification body for this standard. Certification involves testing of representative samples in an accredited laboratory, followed by factory inspections and periodic follow-up testing.
4.1 Testing Process
Manufacturers must submit samples for all intended ratings and variations. The testing typically includes:
- Temperature accuracy and drift testing over 1000 hours of continuous operation.
- Endurance testing under rated load.
- Dielectric withstand and insulation resistance tests.
- Abnormal operation tests (e.g., locked rotor for motor controls, short-circuit withstand for thermal cutoffs).
Critical: Devices that fail the endurance test due to contact welding or excessive temperature drift cannot be represented as compliant. Manufacturers are advised to conduct thorough pre-compliance testing using worst-case production tolerances before submitting to a certification body.
4.2 Certification Marks and Reports
Once certified, each device bears the CSA mark and may be included in the CSA product listing directory. A certificate of compliance (CC) documents the scope of the certification, including approved ratings, temperature ranges, and any limitations (e.g., “For use in non-combustible enclosures only”).
It is important to note that the standard requires the device to be used within its declared ambient temperature range. Using a device outside this range may void the certification and create a safety hazard.
4.3 Periodic Follow-up
Certified devices are subject to unannounced factory inspections and periodic testing by CSA to ensure continued compliance. Manufacturers must maintain quality control records and data from production testing to demonstrate conformity.
The 2017 edition introduced more stringent requirements for creepage distances and materials flammability compared to previous editions. Transition periods are provided for existing certifications, but all new designs must comply with the 2017 edition.
Frequently Asked Questions
Q: What is the difference between a temperature measuring device and a temperature limiting device under CSA C22.2 No. 165-17?
A: A temperature measuring device is mainly for control or indication (e.g., a thermostat that opens at a set point), while a temperature limiting device is a safety component that interrupts the circuit if a pre-set temperature is exceeded, typically requiring manual or automatic reset. Some devices combine both functions, and they must conform to the applicable requirements for each function.
A: A temperature measuring device is mainly for control or indication (e.g., a thermostat that opens at a set point), while a temperature limiting device is a safety component that interrupts the circuit if a pre-set temperature is exceeded, typically requiring manual or automatic reset. Some devices combine both functions, and they must conform to the applicable requirements for each function.
Q: Can a device certified to CSA C22.2 No. 165-17 be used in the United States?
A: CSA certification is primarily for the Canadian market. For U.S. acceptance, the device would also need to comply with the equivalent American standard (e.g., UL 60730-2-9 for automatic electrical controls) and bear an NRTL marking such as UL or CSA US mark. However, many components are certified under both schemes through a joint program.
A: CSA certification is primarily for the Canadian market. For U.S. acceptance, the device would also need to comply with the equivalent American standard (e.g., UL 60730-2-9 for automatic electrical controls) and bear an NRTL marking such as UL or CSA US mark. However, many components are certified under both schemes through a joint program.
Q: Does the standard require a specific color or marking for the temperature setting?
A: The standard requires permanent marking of the set point or range, but it does not mandate a specific color code. However, for thermal cutoffs and limiters used in high-temperature applications, the use of an indelible numerical marking or a coded color band is common practice and is acceptable under the standard.
A: The standard requires permanent marking of the set point or range, but it does not mandate a specific color code. However, for thermal cutoffs and limiters used in high-temperature applications, the use of an indelible numerical marking or a coded color band is common practice and is acceptable under the standard.
Q: What are the most common non-conformities found during certification testing?
A: The top three non-conformities are: (1) contact welding or excessive temperature rise under overload conditions; (2) failure to maintain set-point accuracy after endurance cycling; and (3) insufficient creepage distances between live parts and accessible surfaces after moisture conditioning. These can be mitigated through robust design and careful material selection.
A: The top three non-conformities are: (1) contact welding or excessive temperature rise under overload conditions; (2) failure to maintain set-point accuracy after endurance cycling; and (3) insufficient creepage distances between live parts and accessible surfaces after moisture conditioning. These can be mitigated through robust design and careful material selection.
In summary, CSA C22.2 No. 165-17 provides a robust framework for ensuring the safety and reliability of temperature measuring and limiting devices. Compliance with this standard not only fulfills regulatory obligations in Canada but also improves product quality and end-user safety. Engineers and specifiers should refer directly to the latest edition of the standard for complete details and revisit their designs whenever the standard is revised.
— Published 2026