Alex opens the — the standard wire derating chart. It tells him:
Without derating, that 16-amp load would push conductor temperature over the limit. Insulation hardens, cracks, and eventually shorts. wire derating chart
| Number of Conductors | Derating Percentage | | :--- | :--- | | 4 - 6 | 80% | | 7 - 9 | 70% | | 10 - 20 | 50% | | 21 - 30 | 45% | Alex opens the — the standard wire derating chart
Use the chart, or rewire the fire later. | Number of Conductors | Derating Percentage |
THHN and THWN have different temperature ratings. THHN is rated for 90°C in dry locations, while THWN is 75°C in wet locations. If you run conduit underground to a shed, that is a "wet location." You must use the 75°C column for your calculations, which lowers the starting ampacity.
Now:
Not so fast.