00crashtest
Senior Member
- Location
- California
- Occupation
- electrician trainee
The National Electric Code allows a service conductor and feeder conductor to be rated at only 83% of the service rating and feeder rating, respectively, as shown in Section 310.15(B)(7) in the 2017 Edition and 310.12 in 2020.
So, the service panels would be rated at 100%. According to the trip curves, the breakers would only trip within the tolerance band, which is roughly 115% to 145% of the rated load for infinite-duration loads, with the nominal trip amount being roughly 125%. Those numbers are a whopping 138.55%, 174.7%, and 150.6% of the service/feeder conductors' ratings.
www.c3controls.com
So, in a rare event where all loads add up to exceed the service/feeder conductor ampacity ratings but are not high enough to trip the breaker, who will be liable? For example, a service/feeder conductor burns out and causes a fire before the breaker trips at 138.55%, 150.6%, or 174.7% of the service/feeder conductor rated ampacity.
So, the service panels would be rated at 100%. According to the trip curves, the breakers would only trip within the tolerance band, which is roughly 115% to 145% of the rated load for infinite-duration loads, with the nominal trip amount being roughly 125%. Those numbers are a whopping 138.55%, 174.7%, and 150.6% of the service/feeder conductors' ratings.
c3controls
Trip Curves or Time Current Curves, are an intimidating topic. This paper will introduce you to trip curves and explain how to read and understand them.
So, in a rare event where all loads add up to exceed the service/feeder conductor ampacity ratings but are not high enough to trip the breaker, who will be liable? For example, a service/feeder conductor burns out and causes a fire before the breaker trips at 138.55%, 150.6%, or 174.7% of the service/feeder conductor rated ampacity.
