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| Question on a size of Arc Flash https://brainfiller.com/arcflashforum/viewtopic.php?f=2&t=342 |
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| Author: | Willis [ Thu Feb 19, 2009 7:52 am ] |
| Post subject: | Question on a size of Arc Flash |
Does anyone know what the results would be from a simple small distribution disconnect if it were short circuited and it had an arc flash. How large and destructive of an arc flash could this small of a device actually create? |
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| Author: | Zog [ Thu Feb 19, 2009 8:03 am ] |
| Post subject: | |
Willis wrote: Does anyone know what the results would be from a simple small distribution disconnect if it were short circuited and it had an arc flash. How large and destructive of an arc flash could this small of a device actually create?
Depends on the available fault current and the clearing time of the protective device. Could potentially be a devesating arc flash that can destroy the equipment and injure persons anywhere in the room, or could be very minor and not dangerous, all depends on the factors involved. |
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| Author: | Noah [ Thu Feb 19, 2009 8:45 am ] |
| Post subject: | |
For small disconnect switch, sometime it is hard to find space on the switch to put a lable on. How do you guys deal with those devices? What if you have a row switches on the wall for pump/motor control? |
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| Author: | Willis [ Thu Feb 19, 2009 8:52 am ] |
| Post subject: | |
Clearing time What do you mean "clearing time"? |
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| Author: | Zog [ Thu Feb 19, 2009 9:56 am ] |
| Post subject: | |
Willis wrote: What do you mean "clearing time"?
How long it takes the fuse or breaker to clear the fault at different fault current levels. |
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| Author: | Willis [ Thu Feb 19, 2009 10:45 am ] |
| Post subject: | |
Thanks! I appreciate the information Zog. |
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| Author: | Zog [ Thu Feb 19, 2009 12:02 pm ] |
| Post subject: | |
Welcome to the forum. |
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| Author: | WDeanN [ Thu Feb 19, 2009 2:36 pm ] |
| Post subject: | |
How small is a small disconnect? If its fed by < 30A molded case breaker, it is likely to be < 4 cal/cm. If it's fed by a 600A drawout breaker at a unit substation, it could be > 40 cal. We actually have a case like this, where the breaker is used to feed several things, including a 70A 480V welding receptacle that is now >40 cal because they chose to feed it directly from the UnitSub. Noah, if there is a wire trough above the disconnect rack, I would consider putting the label there, although I have also covered the factory markings at times (I do my best not to, though.) |
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| Author: | Willis [ Thu Feb 19, 2009 2:54 pm ] |
| Post subject: | |
How small is a small disconnect? If its fed by < 30A molded case breaker, it is likely to be < 4 cal/cm. If it's fed by a 600A drawout breaker at a unit substation, it could be > 40 cal. We actually have a case like this, where the breaker is used to feed several things, including a 70A 480V welding receptacle that is now >40 cal because they chose to feed it directly from the UnitSub. What is the cal/cm range that an arc flash becomes deadly or cause serious injury? |
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| Author: | Zog [ Thu Feb 19, 2009 6:46 pm ] |
| Post subject: | |
Willis wrote: What is the cal/cm range that an arc flash becomes deadly or cause serious injury?
1.2 cal/cm2 will cause second degree burns in 1/10th of a second. Put you in a burn unit, life changing event. |
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