Code Change Summary: New code section on selective coordination.
Selective Coordination is defined in Article 100 as the localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the available fault current, and for the full range of overcurrent protective device opening times associated with those overcurrents.
Selective coordination ensures that the overcurrent protective device (OCPD) closest to a fault condition opens first when the fault occurs. When OCPD’s are selectively coordinated, the downstream OCPD closest to the fault will open before any upstream OCPD’s recognize the fault condition and open. A fault on a 20-amp branch circuit should open the 20-amp branch circuit breaker before the main circuit breaker supplying the entire panelboard opens and de-energizes the entire panelboard which supplies other loads that might be important.
The NEC® requires selective coordination between OCPD’s in several locations including:
In the 2023 NEC®, new Section 240.11 was added to address situations where some feeder OCPD’s supplied by a service OCPD require selective coordination while other feeder OCPD’s supplied by the same service OCPD do not.
This new language applies if one or more feeder OCPD’s are required to be selectively coordinated with a service overcurrent protective device by other requirements in the NEC®. When this occurs, all feeder OCPD’s supplied directly by the service OCPD must be selectively coordinated with the service OCPD.
If selective coordination is required in the NEC® between a service OCPD and a feeder OCPD supplied by the service OCPD, having achieved the required selective coordination is beneficial to the system design but there may still be risk of other feeder OCPD’s affecting the design if they are not also selectively coordinated to the service OCPD.
It is very common to have several feeder OCPD’s supplied by the service main OCPD; one of which may require selective coordination while the others may not (see image).
This new code section is meant to assure that the service main OCPD will not open due to an overcurrent condition on a feeder that is not required by the NEC® to selectively coordinate with the service main OCPD.
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC® edition of NFPA 70.
2020 Code Language:
This code section did not exist.
2023 Code Language:
N 240.11 Selective Coordination. If one or more feeder overcurrent protective devices are required to be selectively coordinated with a service overcurrent protective device by other requirements in this Code, all feeder overcurrent protective devices supplied directly by the service overcurrent protective device shall be selectively coordinated with the service overcurrent protective device.
Which of the following is true in new Section 240.11?
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