Timeline for Which breaker should trip with a ground fault with a subpanel?
Current License: CC BY-SA 3.0
7 events
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| Feb 1, 2016 at 15:55 | history | edited | ArchonOSX | CC BY-SA 3.0 |
removed instantaneous for accuracy
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| Feb 1, 2016 at 13:39 | comment | added | Tester101 | I've added what I feel is a fairly accurate example to my answer. | |
| Feb 1, 2016 at 10:45 | comment | added | ArchonOSX | True, but that wire is going to be considerably larger and have much less resistance. 200' of #4 has .05 ohms of resistance. Considering that. If the fault were to occur in the feeder or closer to the sub-panel the fault current would be considerably higher. | |
| Jan 31, 2016 at 23:48 | comment | added | Tester101 | a 50' circuit would only be 25' away from the panel (along the wire). You also have to consider the circuit from the main panel to the second panel, and back. | |
| Jan 31, 2016 at 23:29 | comment | added | ArchonOSX | Yes, but that is at 200 feet of #14 that would be at the extreme of most dwelling units. The average would usually be closer to the 50 feet so almost 1000 amps or even more if it was #12 wire. Certainly the magnetic trip will come in well before the thermal trip at these levels. It would be nice if the smallest breaker trips first but I wouldn't bet a paycheck on it. | |
| Jan 31, 2016 at 22:23 | comment | added | Tester101 | 238 amperes is only 1.19 times the rated current of a 200 ampere breaker, and 2.38 times the 100 ampere breakers. That's likely far below the instantaneous trip rating. | |
| Jan 31, 2016 at 18:03 | history | answered | ArchonOSX | CC BY-SA 3.0 |