# External Disconnect Enclosure



## Michigan Master (Feb 25, 2013)

Anyone see these utilized often on control panels?

I understand the purpose to be twofold:

1. Eliminate the debate concerning if a panel can be classified as effectively locked out despite still having voltage on the line side of the disconnect (dead-front vs. finger-safe and the fact that guarding only reduces arc flash probability, not severity).

2. Allow the arc flash incident energy for this control panel to be calculating ‘including main’ which would reduce the IE. Typically the calculation is done ‘excluding main’ in case there were to be an arc event that propagated to the line side of the device and therefore the next upstream OCPD would be relied upon to clear the fault.


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## don_resqcapt19 (Jul 18, 2010)

It is my opinion that working in that panel with the line side energized would require arc-flash PPE based on the available fault current at the line side of the disconnect and the clearing time of the upstream breaker. If the feeder has much length, incident energy may be high because the impedance of the feeder will limit the fault current and increase the tripping time of the upstream device.


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## Big John (May 23, 2010)

A lot of companies are getting smarter and starting to engineer arc-flash safety into their products. I'm waiting for us to do like Canada and start requiring the same isolation on residential panels.

As an aside, while that picture is awfully pretty, I gotta wonder if it wouldn't have been much cheaper to slap a 3R safety switch onto it and call it good. :laughing:


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