2014 National Electrical Code
Many systems were completely designed using only instantaneous trip circuit breakers. That complied with the code, but was not making use of available safer technology.
The new code requires safer technology to be used for any circuit using a circuit breaker that can be set at 1200
amps or more. This does not apply to circuits with fuses 1200 amps or larger. This white paper discusses changes in overcurrent and surge protection.