Question

Question: I have always calculated loads using 80% of the equipment rating providing the wire is sized properly and recently I have been questioned about where that is in the code book. Well, I have read Article 220 until I am red in the face and can't find it, so I am either in the wrong section or I am off my rocker. Help!!!!!!!!!!!!!!

Answer 1

You are not in the wrong section, but you have misquoted the National Electrical Code (NEC). The NEC actually requires that loads be calculated at 125 percent of the equipment rating, not 80 percent.

NEC 220.87 states:> "Loads calculated for branch circuits as specified in 220.85 shall not exceed 125 percent of the noncontinuous load or 100 percent of the continuous load."This means that when calculating the load on a branch circuit, you must increase the load by 25 percent for non-continuous loads and by 100 percent for continuous loads. This is done to ensure that the branch circuit is not overloaded and that the equipment is properly protected.In addition, NEC 220.61 states that:> "The ampacity of conductors shall be sufficient to carry the maximum load as determined by 220.85 through 220.
88."This means that the wire size must be chosen based on the calculated load, taking into account the 125 percent or 100 percent increase.

Example:

Let's say you have a 10-amp motor that is a non-continuous load. To calculate the load on the branch circuit, you would multiply the motor rating by 125 percent:

Load = 10 amps x 1.25 = 12.5 amps

You would then need to choose a wire size that is rated for at least 12.5 amps.It is important to note that the 125 percent and 100 percent requirements are only applicable to branch circuits. Service calculations and feeder calculations use different methods. Flag for review

Answer 2

You are not in the wrong section, but you have misquoted the National Electrical Code (NEC). The NEC actually requires that loads be calculated at 125 percent of the equipment rating, not 80 percent.

NEC 220.87 states:> "Loads calculated for branch circuits as specified in 220.85 shall not exceed 125 percent of the noncontinuous load or 100 percent of the continuous load."This means that when calculating the load on a branch circuit, you must increase the load by 25 percent for non-continuous loads and by 100 percent for continuous loads. This is done to ensure that the branch circuit is not overloaded and that the equipment is properly protected.In addition, NEC 220.61 states that:> "The ampacity of conductors shall be sufficient to carry the maximum load as determined by 220.85 through 220.
88."This means that the wire size must be chosen based on the calculated load, taking into account the 125 percent or 100 percent increase.

Example:

Let's say you have a 10-amp motor that is a non-continuous load. To calculate the load on the branch circuit, you would multiply the motor rating by 125 percent:

Topic: Load Calculations