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CAN CSA C50089-99 (2016): Low-Voltage Circuit-Breakers for Overcurrent Protection in Household and Similar Installations
Scope, Technical Requirements, and Compliance for Miniature Circuit-Breakers According to the Canadian Standard
CAN CSA C50089-99 (2016) is the Canadian national adoption of the international standard IEC 60898-1 for low-voltage circuit-breakers used for overcurrent protection in household and similar installations. This standard, originally published in 1999 and reaffirmed in 2016, ensures alignment with modern electrical safety and performance requirements across Canada.
Scope and Application
The standard applies to air-break circuit-breakers designed for operation by uninstructed persons, with rated voltages up to 415 V AC (50/60 Hz) and rated currents up to 125 A. These devices are intended for use in residential, commercial, and light industrial settings where protection against overloads and short circuits is required. The circuit-breakers covered are typically of the miniature circuit-breaker (MCB) type, either fixed or plug-in mounting, and are suitable for use in enclosures or distribution boards.
The standard also covers circuit-breakers that incorporate both overcurrent and residual current protection (RCBOs) when conforming to the relevant parts of the IEC 61009 series; however, the primary scope remains on overcurrent protection.
Important exclusions: Molded-case circuit-breakers (MCCBs) are covered by a separate standard (CSA C22.2 No. 5), and high-voltage equipment is outside the scope. The standard does not apply to circuit-breakers for DC circuits unless specifically designed and tested in accordance with additional requirements.
Scope Note: CAN CSA C50089-99 (2016) ensures that circuit-breakers intended for household and similar use meet consistent safety and performance criteria across Canada, harmonized with international practice.
Technical Requirements
Classification and Ratings
Circuit-breakers under this standard are classified according to their overcurrent trip characteristic (B, C, or D), rated current (In), rated short-circuit capacity (Icn), and rated voltage (Ue). Table 1 summarizes the standard preferred values.
| Parameter | Standard Values / Ranges |
|---|---|
| Rated voltage (Ue) | 230/400 V AC (single/three-phase), also 120/240 V AC for North American practice |
| Rated current (In) | 6, 10, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125 A (preferred series) |
| Rated short-circuit capacity (Icn) | 1.5, 3, 6, 10, 15, 25 kA (depending on application) |
| Insulation voltage (Ui) | Minimum 500 V AC |
| Number of poles | 1, 2, 3, 4 (with or without protected neutral) |
Overcurrent Trip Characteristics
The operating time–current curves define the zones within which the circuit-breaker must trip under overload and short-circuit conditions. The standard defines three common trip characteristics (B, C, D) and may include others for specific installations. Table 2 gives the instantaneous trip thresholds and typical application.
Load Selection: The choice of trip curve must match the connected load to avoid nuisance tripping while still providing adequate protection. For example, motors and transformers often have high inrush currents requiring a C or D curve.
| Trip Characteristic | Instantaneous Trip Range (multiples of In) | Typical Application |
|---|---|---|
| B | 3 In to 5 In | Resistive loads, general lighting, socket outlets |
| C | 5 In to 10 In | Mixed inductive and resistive loads, small motors, fluorescent lighting panels |
| D | 10 In to 20 In | Highly inductive loads, transformers, welding equipment, motor starters |
In addition to the instantaneous trips, the standard specifies conventional overload trip times: for currents above the rated current but below the instantaneous threshold, the circuit-breaker must operate within certain time limits (e.g., >1 hour for In and <1 hour for 1.45 In under reference conditions) to protect the cable insulation.
Dielectric and Insulation Requirements
Circuit-breakers must withstand a dielectric test at 2,000 V AC (or 2,500 V for rated voltage >300 V) between live parts and between live parts and exposed conductive parts. The minimum creepage and clearance distances are defined for the rated insulation voltage.
Breaking Capacity and Service Performance
The rated short-circuit capacity (Icn) is verified by type tests. The circuit-breaker must interrupt the fault current and subsequently withstand the prescribed dielectric tests. For Icn values, the standard distinguishes between the ultimate short-circuit capacity (Icu) and service short-circuit capacity (Ics). The standard requires that after breaking the test fault, the device shall operate correctly at 80% of Icn for Ics.
Coordination Consideration: For selective coordination with upstream devices, the circuit-breaker’s let-through energy (I²t) and peak current characteristics must be considered in system design.
Marking and Instructions
Each circuit-breaker must be permanently marked with: manufacturer’s name or trademark, type designation, rated voltage and current, breaking capacity, trip characteristic symbol (B, C, D), and relevant standard reference (CAN CSA C50089-99). The marking must be legible and durable.
Implementation Highlights
When designing or installing electrical systems using circuit-breakers conforming to CAN CSA C50089-99 (2016), several practical aspects should be considered:
- Load Type: Match trip curve to load inrush characteristics. Use B curve for purely resistive loads, C for general lighting and small motors, D for high inductive loads.
- Ambient Temperature: The thermal trip element is temperature-sensitive. For installations where ambient temperature deviates from 30 °C (reference), current-carrying capacity must be derated.
- Mounting and Integration: Devices are designed for mounting on standard DIN rails or in specific enclosures. Ensure adequate ventilation for heat dissipation.
- Discrimination: Plan coordination by selecting devices with appropriate time-current characteristics to minimize service interruption.
- DC Applications: If using these circuit-breakers for DC circuits (e.g., photovoltaic systems), additional testing per Part 2 of the standard may be required. Verify DC rating and polarity.
Compliance and Certification
To claim compliance with CAN CSA C50089-99 (2016), circuit-breakers must undergo type testing by an accredited laboratory. The tests include verification of: dielectric properties, temperature rise under rated conditions, short-circuit performance (both Icu and Ics), endurance (mechanical and electrical), and trip characteristic accuracy.
Certification by a recognized body such as CSA Group or Intertek provides confidence that the product meets the standard. In Canada, provincial electrical codes (e.g., Canadian Electrical Code, CSA C22.1) often require that circuit-breakers be listed or certified to this standard (or other applicable CSA standards) for use in permanent installations.
Safety Warning: Never substitute a circuit-breaker with one having a higher interrupting rating or different trip curve without verifying system coordination and protection requirements. Incorrect selection can lead to electrical fires or equipment damage.
Manufacturers must maintain consistency of production through routine tests and quality management systems. The standard also references requirements for reliability and environmental performance, including resistance to heat, fire, and tracking.
Transition and Maintenance
As CAN CSA C50089-99 (2016) is a reaffirmed standard, users should stay informed about any amendments or new editions, such as the adoption of more recent IEC versions. Regular review of certified products and updated standards is recommended.
Frequently Asked Questions
Q: How does CAN CSA C50089-99 (2016) differ from IEC 60898-1?
A: The CSA standard is technically equivalent to IEC 60898-1 but includes Canadian national deviations, such as voltage ratings (120/240 V) and compatibility with Canadian Electrical Code requirements. Both share the same trip curve definitions and testing methods.
A: The CSA standard is technically equivalent to IEC 60898-1 but includes Canadian national deviations, such as voltage ratings (120/240 V) and compatibility with Canadian Electrical Code requirements. Both share the same trip curve definitions and testing methods.
Q: Can I use a circuit-breaker rated to this standard outdoors?
A: The standard does not specifically restrict installation environment, but the device must be installed in an enclosure rated for the environment (e.g., weatherproof). Additional protections against moisture and corrosion may be needed.
A: The standard does not specifically restrict installation environment, but the device must be installed in an enclosure rated for the environment (e.g., weatherproof). Additional protections against moisture and corrosion may be needed.
Q: Are DC circuit-breakers covered by this standard?
A: CAN CSA C50089-99 (2016) primarily addresses AC circuit-breakers. For DC pole systems, refer to Part 2 (IEC 60898-2) which introduces DC ratings and arc extinction requirements. Some CSA certified products may cover both AC and DC.
A: CAN CSA C50089-99 (2016) primarily addresses AC circuit-breakers. For DC pole systems, refer to Part 2 (IEC 60898-2) which introduces DC ratings and arc extinction requirements. Some CSA certified products may cover both AC and DC.
For further information, consult the official CSA Store for the full text of CAN CSA C50089-99 (R2016).
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