Skip to main content
Home Improvement

Return to Answer

removed instantaneous for accuracy
Source Link
ArchonOSX
ArchonOSX
  • 20.6k
  • 3
  • 29
  • 52

Short answer: The fastest (more sensitive) breaker will trip first.

This isn't necessarily the smallest. Which is why the code has refers to "Selective Coordination". See the definition in Article 100.

Coordination (Selective) Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcur rent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maximum available fault cur rent, and for the full range of overcur rent protective device opening times associated with those overcorrects.

50 feet of #14 is only .126 ohms giving you a short circuit current of 952 amps at 120 volts during a ground fault or short circuit. Even 200 feet of #14 is still 238 amps in excess of the instantaneous trip ratings of all the breakers all the way back your main in the house if you have a 200 amp panel. As the wire gets larger the short circuit current only goes up from there since the resistance and impedance drops.

Short answer: The fastest (more sensitive) breaker will trip first.

This isn't necessarily the smallest. Which is why the code has refers to "Selective Coordination". See the definition in Article 100.

Coordination (Selective) Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcur rent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maximum available fault cur rent, and for the full range of overcur rent protective device opening times associated with those overcorrects.

50 feet of #14 is only .126 ohms giving you a short circuit current of 952 amps at 120 volts during a ground fault or short circuit. Even 200 feet of #14 is still 238 amps in excess of the instantaneous trip ratings of all the breakers all the way back your main in the house if you have a 200 amp panel. As the wire gets larger the short circuit current only goes up from there since the resistance and impedance drops.

Short answer: The fastest (more sensitive) breaker will trip first.

This isn't necessarily the smallest. Which is why the code has refers to "Selective Coordination". See the definition in Article 100.

Coordination (Selective) Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcur rent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maximum available fault cur rent, and for the full range of overcur rent protective device opening times associated with those overcorrects.

50 feet of #14 is only .126 ohms giving you a short circuit current of 952 amps at 120 volts during a ground fault or short circuit. Even 200 feet of #14 is still 238 amps in excess of the trip ratings of all the breakers all the way back your main in the house if you have a 200 amp panel. As the wire gets larger the short circuit current only goes up from there since the resistance and impedance drops.

Source Link
ArchonOSX
ArchonOSX
  • 20.6k
  • 3
  • 29
  • 52

Short answer: The fastest (more sensitive) breaker will trip first.

This isn't necessarily the smallest. Which is why the code has refers to "Selective Coordination". See the definition in Article 100.

Coordination (Selective) Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcur rent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maximum available fault cur rent, and for the full range of overcur rent protective device opening times associated with those overcorrects.

50 feet of #14 is only .126 ohms giving you a short circuit current of 952 amps at 120 volts during a ground fault or short circuit. Even 200 feet of #14 is still 238 amps in excess of the instantaneous trip ratings of all the breakers all the way back your main in the house if you have a 200 amp panel. As the wire gets larger the short circuit current only goes up from there since the resistance and impedance drops.