Confusion on 3-phase Transformer

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Ohms outlaw

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Latrobe pa.
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I am the only electrician in a small Ceramics plant. My predecessor installed this Transformer. It is fed from 480 and is being used to create 110 volt power for all the computers in the building. The part where I am super confused is it is fed by both a 200 amp 3 phase panel and it is also fed by a 100 amp 3 phase panel. The 100 amp disconnect that is feeding into it on one side is coming off of a busbar. The 200 amp disconnect that feeds into the other side is coming all the way from the main distribution panel. The output of the Transformer is going into the computer breaker panel. I cannot shut it off therefore I cannot open it. I did however measure the amperage that it is consuming from its two different feeds. The 200 amp feed is pulling approximately 10 amps per leg and the 100 amp feed is pulling approximately 4 amps per leg. I am by no means a newbie electrician but I am stumped at this point. When I first saw it I thought that one of the feeds is surely abandoned but this is not the case as they are both pulling amperage. Does this setup makes sense to anyone? It seems to me based on the KVA that either one of the two feeds is oversized. If this setup makes sense to anyone please explain it to me thanks in advance.

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JFletcher

Senior Member
Location
Williamsburg, VA
wag, but it sounds like someone tapped the xfmr on the primary side to feed the 100A 480V subpanel.

eta: that, or the 200A panel feed was insufficient so a second feed from the 100A panel was run.
 

Ohms outlaw

Member
Location
Latrobe pa.
Hold the phones I just figured it out. The 100 amp disconnect that I thought was fed from the bus box is not going to the bus box anymore. It was formerly being used to feed whatever Transformer was formally in the same spot. It has now been reused to feed through the power to another 480 volt kiln. I missed the spot where they cut in and 90 out whenever I was tracing the conduit. They also forgot to relabel the disconnect. So the bottom line is that 200 amps is feeding a 45 KVA transformer feeding through to 100 amp disconnect and out to another machine. So it seems my only problem is that there is absolutely no appropriate fuse protection for the Transformer. I went back and took another look at it because as I was writing the post I realized if both were feeding it they would both have equal draw. Oh well fool me once I guess. Now all I have to do is figure out how to protect the Transformer and still feed the other load.

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Ohms outlaw

Member
Location
Latrobe pa.
wag, but it sounds like someone tapped the xfmr on the primary side to feed the 100A 480V subpanel.

eta: that, or the 200A panel feed was insufficient so a second feed from the 100A panel was run.
You nailed it while I was writing my second post. It fooled me because the disconnect used to feed it in the past and they never relabeled the disconnect. thanks for the reply

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