I have a confusing NEC question.
I have an air compressor and a microwave oven that are rated over 12 amps and have a 15-amp plug. They are UL listed. UL seems to say that this is OK because they are not "continuous" loads (3 hours or more).
The NEC indicates the requirements for overcurrent protection (Section 210-20) for branch circuit wiring and permits the concept on continuous and noncontinuous loads to influence the loading of these wires. The overcurrent protection is based on 100 percent of noncontinuous loads and 80 percent of continuous loads. The NEC indicates requirements for loading specific circuits based on the receptacle and branch circuit rating (Section 210-23) that does not take into account continuous and noncontinuous loads when 2 or more receptacles are connected to the branch circuit. Table 210-21 indicates the maximum loads permitted (12 amps for a 15-amp rated branch circuit).
Because the section 210-20 says conductors and equipment (the definition of equipment includes appliances) there seems to be a conflict between these sections.
How is this resolved and why does UL list and inspectors accept products rated for more than 12 amps with a 15 amp plug?
Donald P Grob
Edited to remove E-mail address.
[ October 04, 2005, 10:12 PM: Message edited by: ryan_618 ]
I have an air compressor and a microwave oven that are rated over 12 amps and have a 15-amp plug. They are UL listed. UL seems to say that this is OK because they are not "continuous" loads (3 hours or more).
The NEC indicates the requirements for overcurrent protection (Section 210-20) for branch circuit wiring and permits the concept on continuous and noncontinuous loads to influence the loading of these wires. The overcurrent protection is based on 100 percent of noncontinuous loads and 80 percent of continuous loads. The NEC indicates requirements for loading specific circuits based on the receptacle and branch circuit rating (Section 210-23) that does not take into account continuous and noncontinuous loads when 2 or more receptacles are connected to the branch circuit. Table 210-21 indicates the maximum loads permitted (12 amps for a 15-amp rated branch circuit).
Because the section 210-20 says conductors and equipment (the definition of equipment includes appliances) there seems to be a conflict between these sections.
How is this resolved and why does UL list and inspectors accept products rated for more than 12 amps with a 15 amp plug?
Donald P Grob
Edited to remove E-mail address.
[ October 04, 2005, 10:12 PM: Message edited by: ryan_618 ]
