Ampacity corrections

[Aza]

I have a question on ampacity adjustments. In regards to conductor bundling or ambient temp adjustments. Once that calculation is made do I then have to reduce my over current protection device or increase my conductor size? Thanks again.

 

[augie47]

Either or possibly neither and to complicate matters 110.14 has a bearing.
Your conductor must be protected at its ampacity. Once the appropriate derating factors are applied you protect the conductor according to that number.
Most times conductors are required to be terminated at their 75° rating (110.14)so if you are using a 90° conductor you might be able to derate and still terminate at the 75° rating.
If, after you derate, the conductor does not have adequate amapcity you can either decrease the overcurrent device, if your load allows, or increase the wire size.

 

[DrSparks]

I have a question on ampacity adjustments. In regards to conductor bundling or ambient temp adjustments. Once that calculation is made do I then have to reduce my over current protection device or increase my conductor size? Thanks again.

The first step is to determine the minimum circuit ampacity of the load you are powering. By code the the ampacity of the conductor as well as the overcurrent protection device cannot be less than this. Your adjusted ampacity cannot be less than the minimum ampacity of the circuit. So you can't just put a smaller breaker in to satisfy the derating requirements. So in short you must run bigger wires

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