The IEC 61439 standard is the cornerstone of modern low voltage switchgear design, testing, and compliance. For manufacturers, engineers, and procurement professionals, understanding this standard is not optional—it is essential to ensuring safety, performance, and regulatory acceptance in global markets.
In this guide, we break down what IEC 61439 covers, how it differs from its predecessor IEC 60439, and what you need to verify when sourcing or certifying low voltage switchgear.
What Is IEC 61439?
IEC 61439 is the international standard for low voltage switchgear and controlgear assemblies (LV Assemblies). It defines the design verification, routine testing, and performance requirements for electrical distribution panels, switchboards, motor control centers, and other low voltage equipment.
The standard was developed by the International Electrotechnical Commission (IEC), a global organization that publishes consensus-based standards for electrical and electronic technologies.
Why IEC 61439 Replaced IEC 60439
IEC 60439, the previous standard, used a prescriptive approach—specifying exact construction methods. IEC 61439 shifts to a performance-based methodology. Instead of dictating how to build switchgear, it defines what the equipment must achieve under test conditions.
This change allows manufacturers greater design flexibility while maintaining rigorous safety and performance benchmarks.
Key Parts of IEC 61439
IEC 61439 is a multi-part standard. The most important sections include:
IEC 61439-1: General Rules
This is the foundational document that applies to all LV assemblies. It covers:
- Definitions and classification of assemblies
- Service conditions (ambient temperature, altitude, humidity)
- Electrical ratings (voltage, current, short-circuit withstand)
- Construction requirements (enclosures, busbars, internal segregation)
- Performance requirements and test methods
IEC 61439-2: Power Switchgear and Controlgear Assemblies
This part applies to power switchgear assemblies (PSAs), including main distribution boards, sub-distribution boards, and power control centers. It specifies additional requirements for:
- Current-carrying capacity of busbar systems
- Short-circuit withstand strength
- Electromagnetic compatibility (EMC)
IEC 61439-3: Distribution Boards
This part addresses final distribution boards intended for use by ordinary persons, typically rated up to 250 A. It includes requirements for consumer units and similar assemblies.
Other Relevant Parts
- IEC 61439-4: Assemblies for construction sites (ACS)
- IEC 61439-5: Assemblies for power distribution in public networks
- IEC 61439-6: Busbar trunking systems (busways)
Design Verification Requirements
Under IEC 61439, manufacturers must verify their assemblies through a combination of testing, calculation, and design rules. The standard recognizes three methods:
1. Testing
Physical tests performed on representative samples. This is the most reliable method but also the most expensive. Key tests include:
- Temperature-rise test (10.10)
- Short-circuit withstand strength (10.11)
- Dielectric properties (10.9)
- IP code verification (10.3)
- Mechanical operation (10.13)
2. Comparison with a Reference Design
If a tested reference design exists, manufacturers can compare new designs against it, provided key parameters (materials, dimensions, current paths) are equivalent or more conservative.
3. Assessment
For certain design aspects, verified calculations and design rules can replace physical testing. This is permitted for temperature-rise, short-circuit withstand, and dielectric properties under specific conditions.
Temperature Rise and Derating Factors
One of the most critical aspects of IEC 61439 is temperature-rise verification. Excessive heat degrades insulation, reduces equipment lifespan, and can cause fires.
The standard specifies maximum temperature-rise limits for various materials and components:
- Busbars (bare copper): 60 K above ambient
- Terminals for external insulated cables: 70 K
- Insulated conductors (PVC): 70 K
- Manual operating means (metal): 25 K
When specifying low voltage switchgear for high-temperature environments, always request derating data from the manufacturer.
Short-Circuit Withstand Verification
IEC 61439 requires that busbar systems and connections withstand the mechanical and thermal stresses of short-circuit currents without hazardous deformation or rupture.
The standard introduces rated short-time withstand current (Icw) and rated peak withstand current (Ipk). These values must be clearly marked on the nameplate and supported by test reports.
For projects in the United States, the Underwriters Laboratories (UL) standard UL 1558 is commonly referenced alongside IEC 61439 for switchgear certification.
Internal Separation and Form of Separation
IEC 61439 defines four forms of internal separation based on the degree of compartmentalization:
- Form 1: No separation
- Form 2: Separation of busbars from functional units
- Form 3: Separation of busbars and functional units from each other, but terminals not separated
- Form 4: Full separation of busbars, functional units, and terminals
Form 4 provides the highest level of protection against internal arc faults and is often specified for critical infrastructure, data centers, and healthcare facilities.
IP Codes and Environmental Suitability
IEC 61439 references IEC 60529 for ingress protection (IP) ratings. The standard requires that switchgear enclosures maintain their specified IP rating under all operating conditions.
Common IP ratings for switchgear include:
- IP30-IP41: Indoor commercial installations
- IP42-IP54: Industrial environments with dust or moisture
- IP55-IP65: Outdoor or harsh industrial environments
Learn more about IP ratings and their differences for electrical equipment.
How to Verify IEC 61439 Compliance
When procuring switchgear, request the following documentation from your supplier:
- Type test reports from an accredited laboratory (e.g., KEMA, CESI, SGS, DEKRA)
- Declaration of Conformity (DoC) referencing IEC 61439-1 and the relevant product-specific part
- Routine test certificates for the specific equipment supplied
- Temperature-rise verification data, including derating curves for non-standard ambient temperatures
Beware of suppliers who claim compliance without providing test reports. IEC 61439 is not self-certifying; third-party verification is essential.
IEC 61439 vs. Regional Standards
While IEC 61439 is the global standard, regional standards may also apply:
- United States: UL 891 (switchboards), UL 1558 (metal-enclosed power switchgear)
- Europe: EN 61439 (harmonized with IEC), CE marking under the Low Voltage Directive
- China: GB 7251 series (based on IEC 61439)
- India: IS/IEC 61439
For North American projects, the National Electrical Manufacturers Association (NEMA) publishes supplementary standards referenced by many IEC 61439 tests.
Conclusion
IEC 61439 sets the global benchmark for low voltage switchgear safety and performance. Whether you are a specifier, a contractor, or a procurement manager, understanding this standard enables you to evaluate suppliers, verify claims, and avoid costly compliance failures.
At SwitchGearMFG, all low voltage switchgear and controlgear assemblies are designed, tested, and documented in full compliance with IEC 61439-1, IEC 61439-2, and applicable regional standards. We provide complete type test reports, routine test certificates, and technical support to help your project meet every regulatory requirement.
Contact us today to discuss your project and request a compliance package.