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 Post subject: Multiple disconnects in single enclosure
PostPosted: Tue Mar 10, 2020 9:32 am 

Joined: Tue Mar 10, 2020 9:19 am
Posts: 4
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:
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 Post subject: Re: Multiple disconnects in single enclosure
PostPosted: Tue Mar 10, 2020 12:35 pm 
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Joined: Wed May 07, 2008 5:00 pm
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Location: Rutland, VT
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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 Post subject: Re: Multiple disconnects in single enclosure
PostPosted: Wed Mar 11, 2020 5:59 am 

Joined: Tue Mar 10, 2020 9:19 am
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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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 Post subject: Re: Multiple disconnects in single enclosure
PostPosted: Thu Mar 12, 2020 6:11 am 
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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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 Post subject: Re: Multiple disconnects in single enclosure
PostPosted: Thu Mar 12, 2020 9:41 am 

Joined: Tue Mar 10, 2020 9:19 am
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Does EasyPower have an easy way to do that, or would that have to be done manually?


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 Post subject: Re: Multiple disconnects in single enclosure
PostPosted: Fri Mar 13, 2020 6:33 am 
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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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 Post subject: Re: Multiple disconnects in single enclosure
PostPosted: Fri Mar 13, 2020 7:27 am 

Joined: Tue Mar 10, 2020 9:19 am
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They are all fed from individual 400A breakers on the same MCC bus.


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