Derating Chart Here

20A breaker, THHN, 3 conductors (no bundling derate), ambient 48°C.

If the engineer ignores the chart and draws the full 500W, the PSU will likely overheat, trigger a thermal shutdown, or fail prematurely. derating chart

| Number of Current-Carrying Conductors | Percent of Ampacity | |----------------------------------------|---------------------| | 1-3 | 100% | | 4-6 | 80% | | 7-9 | 70% | | 10-20 | 50% | | 21-30 | 45% | | 31-40 | 40% | 20A breaker, THHN, 3 conductors (no bundling derate),

A is a reference table (usually provided by the NEC, IEC, or a manufacturer) that tells you how much to reduce a component's standard current-carrying capacity (ampacity) under non-ideal conditions. 3 conductors (no bundling derate)