450.3

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Isaiah

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Location
Baton Rouge
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Electrical Inspector
Construction wants to protect two 75kVA dry type transformers 480-120/208V with one, 400A primary over current device. I told them it doesn’t meet NEC 450.3 but they said it’s ok since it’s only for temp construction power...Comments


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So they are wanting to protect them series wired or parallel wired?

🤔
As an EI, let’s say there was a 75kVA already there and later they wanted to add a 75kVA transformer.
How would you allow that?
 
Both are new XFMRs - per 450.3 you have to protect one AND both at 125% or 250% at the same time. Using 400A disc won’t allow it to happen
This is a violation in my opinion and temp power doesn’t make it legal.


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Isaiah said:
Both are new XFMRs - per 450.3 you have to protect one AND both at 125% or 250% at the same time. Using 400A disc won’t allow it to happen
This is a violation in my opinion and temp power doesn’t make it legal.


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If they changed the primary side OCPD to 225A it would work for either one at 250% - and for both at the same time at 125%


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590.2 All Wiring Installations.
(A) Other Articles.
Except as specifically modified in this article, all other requirements of this Code for permanent wiring shall apply to temporary wiring installations.
 
Isaiah said:
Both are new XFMRs - per 450.3 you have to protect one AND both at 125% or 250% at the same time. Using 400A disc won’t allow it to happen
This is a violation in my opinion and temp power doesn’t make it legal.


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I understand both are new transformers… I was trying to get in a thinking moment with you as an electrical inspector.

I agree it’s a violation..
I think Dale and Don have your answer.
 
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