The calculation method is highly valued because it allows manufacturers to verify custom assemblies (like a specific switchboard built for a single project) without destroying a unit in a test lab.
Many modern enclosure manufacturers embed the IEC TR 60890 formulas directly into their free digital design tools.
Verify that the calculated temperature does not exceed the maximum permissible operating temperature specified by the manufacturers of the internal components. Summary of Benefits and Limitations Advantages Limitations Drastically reduces design and compliance validation costs. Limited to assemblies ≤is less than or equal to Accounts for natural air stratification (heat rising).
Calculations addressing outdoor enclosures exposed to direct sunlight. iec tr 60890 pdf
[Gather Component Power Losses] ➔ [Determine Enclosure Dimensions & Installation Type] │ ▼ [Calculate Delta T at Top/Middle/Bottom] ◄─ [Calculate Effective Area (Ae)] │ ▼ [Compare with Max Allowed Component Temperatures] ➔ [Approve Design OR Add Cooling]
The third edition introduced several technical enhancements to improve calculation accuracy:
Annex A of the standard provides that guide users through the entire calculation process, making it easier for engineers to apply the method correctly in practice. The calculation method is highly valued because it
): Calculated based on the physical dimensions of the enclosure and specific surface factors related to how the enclosure is mounted (e.g., against a wall, free-standing). Power Loss (
: It applies to enclosed assemblies or partitioned sections without forced ventilation.
Critical charts determining effective cooling surfaces based on installation types. shortens equipment lifespan
The full title of the standard is "A method of temperature-rise verification of low-voltage switchgear and controlgear assemblies by calculation". Its primary purpose is to determine how much the air temperature inside an enclosure will rise above the ambient temperature due to the power losses of the equipment installed within it. The standard is especially critical for: Enclosed Assemblies:
Evaluating temperature rise is critical when designing and manufacturing low-voltage switchgear and controlgear assemblies. Excessive heat degrades electrical components, shortens equipment lifespan, and poses severe safety hazards. The International Electrotechnical Commission (IEC) addresses this challenge through , a widely recognized Technical Report that outlines a standardized method for calculating temperature rise by extrapolation.
IEC TR 60890:2022 is a technical report providing a standardized, non-physical method for verifying temperature-rise in low-voltage switchgear and controlgear assemblies up to 3,200 A. This third edition offers updated guidance on environmental factors like solar radiation and material effects to support compliance with IEC 61439 standards. The full document can be purchased through the IEC Webstore IEC Webstore IEC TR 60890:2022