mbrooke
Batteries Included
- Location
- United States
- Occupation
- Technician
Can anyone tell me anything about this table from this PDF?
1) Why settle on 400% current as the minimum allowable short circuit current? Time current curves of fuses and breakers indicate that current at 4 times the rating takes about 30-50 seconds to clear. Would this time not be a fire and shock hazard, especially at on circuits 30 amps and below? Id imagine sputtering or arcing would increase this time.
2) Why do they list short circuit currents at 80% of what chapter 9 table 9 indicates?
3) Why do sizes 350kcm and above require calculations? And if so what type/kind of calculations?
I like the concept of such a table, but it seems like it needs more refinement.
1) Why settle on 400% current as the minimum allowable short circuit current? Time current curves of fuses and breakers indicate that current at 4 times the rating takes about 30-50 seconds to clear. Would this time not be a fire and shock hazard, especially at on circuits 30 amps and below? Id imagine sputtering or arcing would increase this time.
2) Why do they list short circuit currents at 80% of what chapter 9 table 9 indicates?
3) Why do sizes 350kcm and above require calculations? And if so what type/kind of calculations?
I like the concept of such a table, but it seems like it needs more refinement.