Graham, I do not understand what you mean. Circuit breakers and fuses give curves for 0.1 to 10,000 seconds. Time to trip or fuse under various "overcurrent" conditions can be very useful, particularly for mechanical loads on motors. BS7671 applies in all installation areas, it may not present data for higher current installations, but has all the principles and regulations for all sizes of jobs. It is true I consider the circuit breaker data on the graph grossly misleading, and it has obviously misled Andy, but manufacturers data can also have the same defect. I wonder if you think that operating a fuse at greater than its "fusing" current is in some way incorrect, the continuous rating of a circuit may be very different from short term conditions, for example for motors starting with a high inertial load, or large incandescent lamps or heating elements.
Graham, I do not understand what you mean. Circuit breakers and fuses give curves for 0.1 to 10,000 seconds. Time to trip or fuse under various "overcurrent" conditions can be very useful, particularly for mechanical loads on motors. BS7671 applies in all installation areas, it may not present data for higher current installations, but has all the principles and regulations for all sizes of jobs. It is true I consider the circuit breaker data on the graph grossly misleading, and it has obviously misled Andy, but manufacturers data can also have the same defect. I wonder if you think that operating a fuse at greater than its "fusing" current is in some way incorrect, the continuous rating of a circuit may be very different from short term conditions, for example for motors starting with a high inertial load, or large incandescent lamps or heating elements.
