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This self-paced online course explains how conductors are sized and selected in the National Electrical Code. In sizing and selecting a conductor multiple factors must be considered.

Upon completion you should be able to:

• Identify the three most significant factors in sizing a conductor.
• Define and explain ampacity.
• Identify the four primary determinants of operating temperature:
  • heat produced by current flow.
  • ambient temperature.
  • ambient medium.
  • adjacent current carrying conductors.
• Explain the methods for determining ampacity.
• Explain how the NEC deals with multiple ampacities.
• Identify the difference between allowable ampacity and true ampacity.
• Identify how the issue of ampacity is dealt with in terms of various issues, including:
  • overcurrent devices.
  • branch circuits.
  • continuous and non-continuous loads.
• Explain how to work with NEC requirements when they result in different required minimum conductor sizes.

Who Will Benefit

Anyone whose job involves designing, reviewing, evaluating or installing fire protection systems, including: designers, installers, engineers, electrical contractors, technicians, project managers, fire marshals, and architects.

Course Summary

• Ampacity, defined as "the maximum current in amperes that a conductor can carry continuously under the conditions of use without exceeding its temperature rating," is extremely important.
• Four “primary determinants of operating temperature” are relevant in many different decisions about conductor size:
  • Heat produced by current flow in the conductor
  • Ambient temperature
  • Ambient medium
  • Adjacent current carrying conductors
• Two primary methods are used to determine ampacity: the table method, which results in "allowable ampacity," and an equation that must be used under engineering supervision, which gives "true ampacity."
• Different methods sometimes yield different values for ampacity of a conductor. When this happens, the lowest value must be used.
• Other factors that must be considered in determining conductor size include the effect on current on overcurrent devices, requirements for branch circuits, whether the load is continuous or non-continuous and specific equipment requirements.