13kV xfmr - room needs 3-hr fire rating?

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malachi constant

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I was under the impression a 13kV 1000kVA transformer, when installed indoors, needs to be in a 3-hr rated vault. Looking at the code I see 450.21(B) requires xfmrs rated over 112.5kVA to be in a 1hr rated room, and 450.21(C) requires (by referencing Part III and 450.42) that transformers rated over 35KV be in a 3-hr rated vault.

So am I correct that the 13kV, 1000kVA transformer, installed indoors, needs a 1-hr rating - not a 3-hr rating?
 
My batting average is not very good today, but would it not depend on the transformer being oil-filled or not ? (I don't see that mentioned by the OP)
 
augie47 said:
. . . would it not depend on the transformer being oil-filled or not ?
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True. Oil filled transformers installed indoors need to be in a vault (there are several exceptions, but they do not apply to the transformer in question). Given that the OP cited 450.21,and not 450.26, I inferred that we are dealing with dry-type. But nothing should be assumed, as they say.
 
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