1600A 480V Stand-Alone Fused Switch

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hillbilly1 said:
I’ve stated that in other threads, but if the main is in the mcc, even with it off, you would still need PPE because of the exposure to the line side. Many conveyor installs are now requiring a disconnect outside the enclosure that totally removes voltage inside. The same would be with the OP’s situation.
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When you go to check the no-power condition in the MCC, the incident energy would be lower due to the protective device at the transformer secondary, so PPE would be easier to achieve.
 
ggunn said:
#18 was the one where I asked the question. The post I was replying to said only "the latest NEC"; the 2023 is the latest published but the 2020 is the latest adopted by most AHJs.
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Oops.
My answer was in #17.
The circuit breaker requirement was back in 2017, the fused switch requirement was new in the 2020 with a delayed implementation date of Jan 2020.
 
jim dungar said:
Oops.
My answer was in #17.
The circuit breaker requirement was back in 2017, the fused switch requirement was new in the 2020 with a delayed implementation date of Jan 2020.
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Ah, the dreaded "delayed implementation", like 230.46, the one that UL had three years to get ready for but didn't.
 
ggunn said:
Ah, the dreaded "delayed implementation", like 230.46, the one that UL had three years to get ready for but didn't.
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But this one was delayed only about 4 months. This was likely more for manufacturer order cycles because no new products were really necessary.
 
jim dungar said:
But this one was delayed only about 4 months. This was likely more for manufacturer order cycles because no new products were really necessary.
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No new products were necessary for 230.46, either, just testing and listing protocols by UL, which they did not deliver in time, although they had three years' notice. I asked an engineer at Ilsco about it and he went on a few minutes rant about UL's foot dragging and how he had submitted products and paperwork well in advance of the deadline. He was not a happy camper.
 
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jim dungar said:
The latest NEC requires a maintenance reduction switch on devices 1200A and larger.
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That's not exactly true. 240.87 for breakers 1200 amps and larger says:

(B) Method to Reduce Clearing Time.
One of the following means shall be provided and shall be set to operate at less than the available arcing current:
(1)Zone-selective interlocking
(2) Differential relaying
(3) Energy-reducing maintenance switching with local status indicator
(4) Energy-reducing active arc flash mitigation system
(5) An instantaneous trip setting. Temporary adjustment of the instantaneous trip setting to achieve arc energy reduction shall not be permitted.
(6) An instantaneous override
(7) An approved equivalent means

So there must be a way to reduce the clearing time, but there are numerous ways to do that besides just a maintenance (MX) switch. MX switch is preferred in my opinion because the system can be set to coordinate under normal operation, and the MX-switch activated when working on it.
 
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