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- Location
- Cary, Illinois
Hey Guys,
I am trying to figure out the Fuse and wire size for a 100 H.P. motor. I am an electrician and I dont do sizing on motors this big often. I think I figured it out from my code book with sizing the time delay fuse at 175% of the nameplate. But the charts that I am finding show the wire much larger than the 125% that the code says.
I have a nameplate rating of 112 A, for a 480 v, three phase motor. It looks like 196 amps, which I would use a 200 amp fuse for, and then I get 140 amps for my wire size that puts me at a #1 at 150 amps THHN. That does not seem right to me and the charts that I am finding tell me that I should be at a 2/0 or a 3/0. What am I missing? And what is correct? Also, I have a fused disconnect in my M.C.C. that is rated up to 200 amps that I was hoping I could use instead of ordering and replacing one for a 225A fuse.
I am trying to figure out the Fuse and wire size for a 100 H.P. motor. I am an electrician and I dont do sizing on motors this big often. I think I figured it out from my code book with sizing the time delay fuse at 175% of the nameplate. But the charts that I am finding show the wire much larger than the 125% that the code says.
I have a nameplate rating of 112 A, for a 480 v, three phase motor. It looks like 196 amps, which I would use a 200 amp fuse for, and then I get 140 amps for my wire size that puts me at a #1 at 150 amps THHN. That does not seem right to me and the charts that I am finding tell me that I should be at a 2/0 or a 3/0. What am I missing? And what is correct? Also, I have a fused disconnect in my M.C.C. that is rated up to 200 amps that I was hoping I could use instead of ordering and replacing one for a 225A fuse.