Two feeders off Transformer secondary to two locations.

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ezdrocks

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Houston, Texas, USA
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I&E Designer, Industrial Electrical and Instrumentation design (NOT an engineer but close)
I've searched online but am having a hard time with this one.

I have a 7,500kva, 12,470x4,160 transformer that I need to feed to two separate locations.

Originally, the secondary was to feed a set of MV MCC gear inside an MCC building. This gear was going to have a breaker to feed out to a 1500kva 4,160x480 transformer. However, the company that specified the MCC gear, did not put in this breaker, and didn't leave room in the building to add one. So now I am trying to figure out how to feed a) The original incoming main on the 4,160 MV MCC Switchgear, and b) The primary side of the 4,160x480 transformer, from the secondary of the first transformer.

I would like to feed both directly off the secondary side of the 12,470x4,160 transformer, but I need to protect the incoming primary on the smaller transformer. I was going to put something like a Square D Mini-Break with a 250A Fused disconnect in line between the first and secondary transformer, but NEC 240.21(C)(3)(3) says "All overcurrent devices are grouped".

The transformers would be next to each-other, and the incoming main inside the MCC building would be within the 25' length, but the overcurrent devices are not grouped.

I looked at 240.21(C)(4) "Outside secondary Conductors", and this seems like a viable option, except I'm questioning point (2), "The conductors terminate at a single circuit breaker of a single set of fuses...". Is this statement saying that there can only be one fuse (or other OCPD) total, or for each set of conductors leaving the transformer secondary?

Thanks for your help.
 
I've searched online but am having a hard time with this one.

I have a 7,500kva, 12,470x4,160 transformer that I need to feed to two separate locations.

Originally, the secondary was to feed a set of MV MCC gear inside an MCC building. This gear was going to have a breaker to feed out to a 1500kva 4,160x480 transformer. However, the company that specified the MCC gear, did not put in this breaker, and didn't leave room in the building to add one. So now I am trying to figure out how to feed a) The original incoming main on the 4,160 MV MCC Switchgear, and b) The primary side of the 4,160x480 transformer, from the secondary of the first transformer.

I would like to feed both directly off the secondary side of the 12,470x4,160 transformer, but I need to protect the incoming primary on the smaller transformer. I was going to put something like a Square D Mini-Break with a 250A Fused disconnect in line between the first and secondary transformer, but NEC 240.21(C)(3)(3) says "All overcurrent devices are grouped".

The transformers would be next to each-other, and the incoming main inside the MCC building would be within the 25' length, but the overcurrent devices are not grouped.

I looked at 240.21(C)(4) "Outside secondary Conductors", and this seems like a viable option, except I'm questioning point (2), "The conductors terminate at a single circuit breaker of a single set of fuses...". Is this statement saying that there can only be one fuse (or other OCPD) total, or for each set of conductors leaving the transformer secondary?

Thanks for your help.
The rule applies separately to each set of transformer secondary conductors.
 
The rule applies separately to each set of transformer secondary conductors.
So I would be okay if one set of conductors goes to a Mini-Break with a fused disconnect and then to the second transformer, and the second set of conductors goes into the building MV MCC incoming main?
 
I've searched online but am having a hard time with this one.

I have a 7,500kva, 12,470x4,160 transformer that I need to feed to two separate locations.

Originally, the secondary was to feed a set of MV MCC gear inside an MCC building. This gear was going to have a breaker to feed out to a 1500kva 4,160x480 transformer. However, the company that specified the MCC gear, did not put in this breaker, and didn't leave room in the building to add one. So now I am trying to figure out how to feed a) The original incoming main on the 4,160 MV MCC Switchgear, and b) The primary side of the 4,160x480 transformer, from the secondary of the first transformer.

I would like to feed both directly off the secondary side of the 12,470x4,160 transformer, but I need to protect the incoming primary on the smaller transformer. I was going to put something like a Square D Mini-Break with a 250A Fused disconnect in line between the first and secondary transformer, but NEC 240.21(C)(3)(3) says "All overcurrent devices are grouped".

The transformers would be next to each-other, and the incoming main inside the MCC building would be within the 25' length, but the overcurrent devices are not grouped.

I looked at 240.21(C)(4) "Outside secondary Conductors", and this seems like a viable option, except I'm questioning point (2), "The conductors terminate at a single circuit breaker of a single set of fuses...". Is this statement saying that there can only be one fuse (or other OCPD) total, or for each set of conductors leaving the transformer secondary?

Thanks for your help.
240.21(C) doesn't apply to your installation at all.
 
You're over 1000V. Check out 240.1 Scope
Well damn...I'm used to dealing with smaller transformers.

So I've moved on to 240.100 now. It looks like I'm okay. Check out this sketch and let me know what you think.
1696015109415.png
 
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