EC&M Tech Talk — Conductors, Insulation, and Calculating Ampacity

In this EC&M Tech Talk master electrician Randy Barnett examines specific tables found in the NEC for selecting and sizing conductors. The Tech Talk begins with an introduction to conductor properties and how to interpret the information found in Chapter 9, Table 8 Conductor Properties. Reading and interpreting the information found in Table 310.4(1) regarding conductor applications and insulations (rated 600 volts) is where it all begins as we must select the correct insulation type for the application before we determine the size wire needed.

Determining the AWG size of the conductor for a specific size load requires some basic calculations which are explained on screen including an example of correcting for temperature and adjusting for the number of conductors in the raceway. In the final calculation a real-world example is given. Using a short-cut formula, Randy walks through selecting a conductor for a 200 Amp load given a typical ambient temperature and four current-carrying conductors in the conduit.

This Tech Talk provides in-depth information into conductors and the code tables for conductor selection and application. It is an excellent discussion for those learning ampacity calculations and preparing for exams.