Transformer disconnect w/ double lugs sketch

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Npstewart

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Hi everyone. I ran into a electrician buddy of mine who is doing an install based on a sketch that an architect drew. He asked my opinion on it to see if it was legal. I re-drew the sketch real quick for purposes of this post. Over-all, this seems legal as long as the load doesen't exceed 200A, but this setup is extremely strange to me. I just wanted to get some opinions on it.


If you are wondering, I have no idea why they bought such a large transformer for such a small load and fused it down to 200A.
 

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Npstewart said:
Hi everyone. I ran into a electrician buddy of mine who is doing an install based on a sketch that an architect drew. He asked my opinion on it to see if it was legal. I re-drew the sketch real quick for purposes of this post. Over-all, this seems legal as long as the load doesen't exceed 200A, but this setup is extremely strange to me. I just wanted to get some opinions on it.


If you are wondering, I have no idea why they bought such a large transformer for such a small load and fused it down to 200A.
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The 2 sets of 3/0 from the xformer seem useless, why not just use 1 set? You may have trouble getting lugs on the disconnect approved for this many conductors and have wire space issues as well. Why not 1 set of 3/0 to the 200 amp disco, then 1 set to the first panel (order it as a feed though), then to to the second panel with 3/0?
 
Maybe they got a deal on the transformer. I don't have a problem with it. If that is what they want to pay you to do, why would you care? I can't see any code violations. as someone mentioned you might have an issue with wiring room for the feeder into the disconnect.
 
I agree that there are probably 3 other ways to do this better. This is not my design though, I just duplicated the sketch that was given to me and was asked to give my opinion. If I were designing this, depending on the specifics, I would have installed a 75 KVA transformer and had one panel, if more spaces were required I would have sub-fed it or done a feed thru.
 
Npstewart said:
I agree that there are probably 3 other ways to do this better. This is not my design though, I just duplicated the sketch that was given to me and was asked to give my opinion. If I were designing this, depending on the specifics, I would have installed a 75 KVA transformer and had one panel, if more spaces were required I would have sub-fed it or done a feed thru.
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Agreed. But I still say you can't put 16, 3/0 conductors in a 200 amp breaker enclosure or even in a safety switch.
 
Does seem a bit silly. For the cost of (1) additional 200 amp disconnect he could double his capacity. Everything else is already size to do so.
 
augie47 said:
Does seem a bit silly. For the cost of (1) additional 200 amp disconnect he could double his capacity. Everything else is already size to do so.
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It would probably cost less than whatever extra gutters it takes to make the wires fit in one disconnect.

I run across this kind of thing now and then. Often, it does not make much sense to me, but sometimes how it came to be almost makes sense when I know the whole story.

We have had customers specify PLC systems that cost tens of thousands of dollars to handle <20 I/O. We make sure that they udnerstand there are more cost effective options, but if that is what they want, that is what they get.
 
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