Alwayslearningelec
Senior Member
- Location
- NJ
- Occupation
- Estimator
When you derate you can't use the 90 degree for conductors landing on terminals if they are rated for 75 degree?
Adjustments and derating
- Thread starter Alwayslearningelec
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Derating is using the conductor insulation maximum temperature value not the terminals. So for something like THHN you can use the 90° C ampacity for your derating calculation.
- Location
- Illinois
- Occupation
- retired electrician
You start with the 90°C ampacity for the ampacity adjustments and corrections. If that results in an ampacity that exceeds the 75°C ampacity, you use the next larger conductor for the installation.