You can't use these calculations for every single panel. For the method to be valid, several conditions must be met: IEC TR 60890:2022
How the enclosure is mounted (e.g., against a wall, free-standing). Ventilation Design:
Utilizing this technical report provides several distinct advantages for electrical designers and manufacturers:
The standard is part of a broader ecosystem of IEC standards for low-voltage assemblies, most notably the , which governs the design and verification of such equipment. It is a product of the work of Subcommittee 121B: Low-voltage switchgear and controlgear assemblies of IEC Technical Committee 121. iec tr 60890 pdf
To perform the calculation, the standard requires data on:
The internal horizontal partitions or shelves must have adequate ventilation openings so they do not completely block the natural convection of air.
For height 1.8m, add ~5K. Final top internal temperature rise = 81 K above ambient . At 35°C ambient, internal air reaches 116°C – which may exceed component limits (typical max 70°C for MCBs). The designer would then need to reduce load or improve ventilation. You can't use these calculations for every single panel
Understanding IEC TR 60890: The Standard for Temperature-Rise Calculation in Low-Voltage Switchgear
You cannot use the IEC TR 60890 calculation for every switchgear design. The standard restricts its application to assemblies that meet strict geometric and operational criteria to ensure the mathematical models remain accurate.
Added dedicated informative annexes for solar load adjustments Assumed linear/even dissipation Includes specialized methods for uneven power distribution Ventilation Scope Restricted to natural convection It is a product of the work of
Because IEC TR 60890 is a copyrighted technical document, users seeking the PDF should prioritize official, licensed sources.
Understanding IEC TR 60890 PDF: Thermal Calculations for Low-Voltage Switchgear
Below is a you can adapt.
The standard has also been adopted globally. For instance, it has been harmonized in Australia and New Zealand as , providing local industries with a proven method for determining temperature rise.