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| Multiple disconnects in single enclosure https://brainfiller.com/arcflashforum/viewtopic.php?f=23&t=5264 |
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| Author: | stew1350 [ Tue Mar 10, 2020 9:32 am ] |
| Post subject: | Multiple disconnects in single enclosure |
I'm trying to figure out how to model a portion of this system. A contractor has recently installed four new motor feeders, and they all pass through a single disconnect enclosure. Each feeder has a 400A breaker at the MCC, and they each also have a 400A breaker in this new enclosure. I imagine the incident energy to be higher than the worst case for any single feeder, but don't think I should add them all together either. Has anybody dealt with something similar? It looks more or less like this: Code: ................................
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| Author: | wbd [ Tue Mar 10, 2020 12:35 pm ] |
| Post subject: | Re: Multiple disconnects in single enclosure |
What software are you using? An arc on any one of the breakers would expand to include all the others. One way is to model the enclosure as a bus on the load side of all the breakers and then fault that bus. I use EasyPower so the bus would be set to ignore the main breakers, on Integrated method and that would give you the incident energy for that box. |
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| Author: | stew1350 [ Wed Mar 11, 2020 5:59 am ] |
| Post subject: | Re: Multiple disconnects in single enclosure |
wbd wrote: What software are you using? An arc on any one of the breakers would expand to include all the others. One way is to model the enclosure as a bus on the load side of all the breakers and then fault that bus. I use EasyPower so the bus would be set to ignore the main breakers, on Integrated method and that would give you the incident energy for that box. I am also using EasyPower. That is how we approach most enclosures, but this equipment has several motors and control panels below it. I don't want to erroneously affect the IE at those panels. Maybe I'll run that as a scenario and see if anything changes significantly. Thanks for the help. |
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| Author: | wbd [ Thu Mar 12, 2020 6:11 am ] |
| Post subject: | Re: Multiple disconnects in single enclosure |
Yes you will have to do a separate analysis for the common enclosure and then do another for the equipment downstream with each feed as it is from the common enclosure. |
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| Author: | stew1350 [ Thu Mar 12, 2020 9:41 am ] |
| Post subject: | Re: Multiple disconnects in single enclosure |
Does EasyPower have an easy way to do that, or would that have to be done manually? |
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| Author: | wbd [ Fri Mar 13, 2020 6:33 am ] |
| Post subject: | Re: Multiple disconnects in single enclosure |
You would have to model it twice but that is not hard. One model would be with the single enclosure with all 4 breakers connected to a bus. The other with the system as it normally is. The single connected bus model would give you the incident energy for that enclosure. Are all 4 breakers in the enclosure fed from the same bus or multiple different buses? |
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| Author: | stew1350 [ Fri Mar 13, 2020 7:27 am ] |
| Post subject: | Re: Multiple disconnects in single enclosure |
They are all fed from individual 400A breakers on the same MCC bus. |
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