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#112492 - 06/30/01 12:02 AM 200 - 225  
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[Linked Image]
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While getting some info for a single-line diagram I found this. Service is 277/480V, 1600A, with a number of 200A &1-400A Fusible Switches. The 400A was fused at 225A. OK. The first 200A Switch was fused at 225A . Huh? I really did a double take on this. The remaining 5- 200A were the same way.
Can you see how they managed this? What would/could happen if these units were called upon to "do their duty?"

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#112493 - 06/30/01 06:35 AM Re: 200 - 225  
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So U have 225A fuses in many 200A disco's. The result of a 'dead short' and subseqent AIC may see the disco, not the fuses, as the weak link.


#112494 - 06/30/01 08:16 AM Re: 200 - 225  
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But the 225A 600V fuses in the 400A disco are way too large to fit in the 200A switch. [Linked Image]


#112495 - 06/30/01 11:00 AM Re: 200 - 225  
sparky  Offline
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yes they are, do you suppose there would also be more of a 'flashover' possibility???


#112496 - 06/30/01 11:56 AM Re: 200 - 225  
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I SURE DO see flashover as a problem. There was a hint in my last post, here's another, a little more obvious 110-4. [Linked Image]


#112497 - 06/30/01 02:55 PM Re: 200 - 225  
sparky  Offline
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no aurgement from me, we could list a few more codes on top of this. my post was stictly speculation, supposing a 'short', not G-fault across two phases fused side by side. they look close!
as a contractor, i find exercising that 'liability node' part of my grey matter to the worst case scenario essential to my survival it's a jungle out there!

[Linked Image]


#112498 - 06/30/01 04:43 PM Re: 200 - 225  
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FRS>FRN, 480>250,(OK, I'll stop this secretive business). These are 250V rated fuses used on a 480V system. They actually fit sickeningly well into the fuse clips. We've included replacing these fuses with 200A, 600V fuses in our bid for the owners' work. If they don't want the work performed, they can't care much about their beautiful 4 story office building.


#112499 - 06/30/01 05:41 PM Re: 200 - 225  
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pardon my ingnorance, now that U mention the obvious, they do look a tad short....

[Linked Image]


#112500 - 07/01/01 10:32 AM Re: 200 - 225  
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I sure hope you're not ignorant, Sparky, because I stood gawking, scratching my head, gawking some more for an awfully long time before I realized what was going on...and I could read the writing on the fuses!! We get so used to seeing things in a certain way that when something looks almost right, it almost passes us by. If you're ignorant, then I'm an absolute moron!


#112501 - 07/01/01 11:02 AM Re: 200 - 225  
sparky  Offline
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Ok, now that we have established the obvious, as applied to the original Q, what would happen if these fuses were called to duty?
In a worst case scenario ( all i can think of is a dead short), would we have the equivalent of 3 grenades?
[Linked Image]


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