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Determining Current Carrying Capacity of Conductors (NFPA Article)

jar546

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The purpose of NFPA 70®, National Electrical Code® (NEC®) is the practical safeguarding of persons and property from the hazards that arise due to the use of electricity. Typically, this means protecting people from hazards like shock and arc flash, as well as property from fire. Fires resulting from improper wiring have historically been a significant threat ever since electrical systems have been installed within buildings. The NEC has established a long history of installation requirements to help prevent fires from occurring within the electrical system. One such requirement is to determine how much electrical current a conductor can carry continuously without exceeding the temperature rating of its insulation, or as the NEC refers to it, a conductor’s ampacity.

However, determining ampacity requires the understanding of a number of other factors that come into play based on how a conductor is used and installed. This involves navigating charts, tables, and a number of other requirements to make sure that we calculate the correct ampacity. Depending on which conditions of installation and use exist, we find ourselves using a number of tables found throughout the NEC, but in particular, many of them are located in Article 310. There are a multitude of tables that spell out items such as conductor ampacity, temperature correction factors, and adjustment factors. So, let’s take a look at how these ampacity charts and tables can be used to ensure we select the appropriate conductor for the installation.

There are a few questions we must ask ourselves before we begin. First, we need to know what the conductor insulation is rated for since ampacity is a function of the temperature rating of the insulation. Once we have established if we are using 60-, 75-, or 90-degree Celsius rated insulation, we can determine which column from the appropriate ampacity chart we need to be in. For conductors rated up to 2000V, ............

For the full article, click here: https://www.nfpa.org/news-blogs-and...ining-current-carrying-capacity-of-conductors
 
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