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Technical Analysis of CAN CSA E60335-2-21-01: Safety Requirements for Household Electric Storage Water Heaters
Comprehensive Guide to Compliance and Implementation for Canadian Manufacturers
Introduction and Scope
CAN CSA E60335-2-21-01 is the Canadian adoption of the international standard IEC 60335-2-21, focusing on safety requirements for household and similar electrical storage water heaters. This standard applies to electric water heaters with a rated voltage not exceeding 250 V for single-phase appliances and 480 V for all other appliances. It covers both vented and unvented storage water heaters designed for domestic use, including those intended for wall mounting or floor standing installations.
The scope includes appliances that are factory-assembled and intended for connection to a cold-water supply. It also addresses water heaters that may incorporate additional functions such as temperature control, overheat protection, and anti-corrosion measures. However, the standard explicitly excludes water heaters intended exclusively for industrial purposes or those that are part of a larger heating system (e.g., heat pump water heaters when evaluated separately).
Note: Manufacturers designing products for the Canadian market must use CAN CSA E60335-2-21-01 as the baseline safety standard. Although it is harmonized with IEC 60335-2-21, Canadian deviations (e.g., for voltage ratings and grounding requirements) may apply.
Key Technical Requirements
Electrical and Thermal Safety
The standard outlines rigorous tests to ensure safe operation under normal and fault conditions. Among the most critical are the heating element endurance test and the temperature rise test. These verify that the water heater does not exceed specified surface temperature limits and that the insulation system remains intact under prolonged electrical load.
All water heaters must incorporate a thermal cut-out device to prevent overheating in the event of thermostat failure. This device must be non-self-resetting (manual reset) to ensure user intervention after an overtemperature event. Additionally, the standard requires protection against the formation of steam pockets that could cause violent boiling (water hammer) or damage to the tank.
Construction and Materials
Key construction requirements include:
- Corrosion resistance – The inside of the tank must be either glass-lined, fitted with a sacrificial anode, or manufactured from corrosion-resistant material.
- Pressure containment – The tank must withstand a hydraulic pressure test at 1.5 times the rated pressure without leakage or permanent deformation.
- Spacing and insulation – Electrical insulation distances must comply with creepage and clearance requirements for pollution degree 2 and overvoltage category II/III as defined in IEC 60335-1.
| Test Item | Requirement | Typical Limit / Criteria |
|---|---|---|
| Hydrostatic pressure test | Tank filled with water, pressure raised to 1.5× rated pressure | No visible leakage or deformation |
| Temperature rise (heating elements) | Energize element at rated voltage; record steady-state temperature | Metal surface temp ≤ 130 °C (thermocouple method) |
| Thermal cut-out operation | Disable primary thermostat; monitor cut-out activation | Shall operate before water temperature exceeds 99 °C (plus allowed tolerance) |
| Leakage current (at operating temperature) | Measure between live parts and accessible metal | ≤ 0.75 mA for cord-connected appliances; ≤ 0.25 mA per hot wire for permanently connected |
| Endurance of expansion device (if any) | Cycle device 10 000 times at rated conditions | No failure or permanent loss of sealing |
Important: The standard requires that all water heaters intended for Canada must be capable of operating on a nominal voltage of 120/240 V, 60 Hz supply unless otherwise marked. Grounding must conform to the Canadian Electrical Code, Part I (CE Code).
Compliance and Certification Pathway for Canada
To demonstrate compliance with CAN CSA E60335-2-21-01, manufacturers typically follow one of two routes:
- Self-declaration with supporting test reports – Acceptable for low-risk products if the manufacturer maintains an ISO 17025-accredited test facility and provides traceable documentation.
- Third-party certification – More common for safety listing. Organizations such as CSA Group, UL (Intertek) or QAI Laboratories can issue certifications valid for the Canadian market. The certification mark (e.g., CSA mark) is widely recognized by provincial regulatory authorities.
When applying for third-party certification, the manufacturer must submit samples, technical documentation (circuit diagrams, component ratings, drawings), and a declaration of conformity to the relevant parts of IEC/CSA 60335-1 (general requirements) and CAN CSA E60335-2-21-01. The certifier will perform the required testing and conduct a factory inspection for initial production consistency.
Success Tip: To accelerate certification, ensure that all key components (thermostats, thermal cut-outs, pressure relief valves, etc.) are already recognized to CSA or UL standards and carry appropriate certification marks.
Caution: Using a component that is not certified for its intended function (e.g., a thermostat listed only for heating and not specifically for water heater service) may lead to test failure and costly redesign. Always verify the component’s certification scope matches the application.
Compliance Notes for Manufacturers
Deviations from IEC 60335-2-21
While closely aligned, CAN CSA E60335-2-21-01 includes several national deviations to address Canadian electrical supply characteristics and installation practices:
- Voltage ratings: Maximum rated voltage for single-phase appliances is 250 V to accommodate 240 V systems; for all other appliances, it is 480 V.
- Grounding: All accessible metal parts must be permanently connected to a grounding conductor. Cord-connected water heaters must use a grounding-type attachment plug.
- Overpressure protection: A pressure relief device must be fitted if the water heater can be isolated from the main supply by a backflow preventer or check valve.
Product Marking and Instructions
Every water heater sold under this standard must be marked with:
- Rated voltage, frequency, and power input (in watts or kW)
- Rated pressure (if applicable)
- Name or trademark of the manufacturer or authorized distributor
- Model and/or serial number for traceability
- Clear indication of the water connection size and location
Installation instructions must include warnings about correct electrical supply, grounding, and the necessity of a dedicated branch circuit as per the CE Code.
Frequently Asked Questions
Q: Can I use a water heater certified to IEC 60335-2-21 (international version) directly in Canada without additional testing?
A: No. While IEC 60335-2-21 forms the technical base, Canadian deviations (especially regarding voltage, grounding, and pressure relief) must be verified. A product certified to the IEC version may still need modification or re-test to comply with CAN CSA E60335-2-21-01.
A: No. While IEC 60335-2-21 forms the technical base, Canadian deviations (especially regarding voltage, grounding, and pressure relief) must be verified. A product certified to the IEC version may still need modification or re-test to comply with CAN CSA E60335-2-21-01.
Q: Does the standard apply to heat pump water heaters?
A: This standard covers resistance-type electric storage water heaters only. Heat pump water heaters (that incorporate a refrigeration cycle) are evaluated under a separate standard, such as CSA C744 or the appropriate heat pump appliance standard.
A: This standard covers resistance-type electric storage water heaters only. Heat pump water heaters (that incorporate a refrigeration cycle) are evaluated under a separate standard, such as CSA C744 or the appropriate heat pump appliance standard.
Q: Is a built-in thermal cut-out considered sufficient overheat protection?
A: Yes, provided the cut-out is non-self-resetting and its opening temperature is below the dangerous threshold (typically ≤99 °C). Additionally, the cut-out must be independent of the main thermostat to prevent both devices failing simultaneously due to a single fault.
A: Yes, provided the cut-out is non-self-resetting and its opening temperature is below the dangerous threshold (typically ≤99 °C). Additionally, the cut-out must be independent of the main thermostat to prevent both devices failing simultaneously due to a single fault.
Q: What about combi boilers that produce both hot water and space heating?
A: Such appliances are reviewed under the applicable standard for water heaters only when operating in the domestic hot water mode. For the space heating function, the relevant standard (e.g., CSA 4.9 or ANSI Z21.13) may also apply. Combinational appliances often require evaluation under multiple standards.
A: Such appliances are reviewed under the applicable standard for water heaters only when operating in the domestic hot water mode. For the space heating function, the relevant standard (e.g., CSA 4.9 or ANSI Z21.13) may also apply. Combinational appliances often require evaluation under multiple standards.
Published: 2026. This article is for informational purposes and does not replace the full text of the standard. Always consult the latest edition of CAN CSA E60335-2-21-01 and relevant Canadian regulations.