Transformer secondary solution lead times

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Dengineer

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Electrical Engineer
Hello all,

I am working on a new mixed use residential/commercial building where we have a 1200A switchgear being fed from a 750KVA transformer. Now we are having issues with lead times for the switchgear that go from 6months to over a year. I have been tasked with finding a cost effective solution and I have a couple of ideas that I would love to run by you guys.

1- Provide double lugs on the secondary side of the transformer and feed (2)600A MCB distribution panels. I'll need to put the panels within 10FT of the transformer or provide redundant fused disconnects within 10 feet of the transformer and run the feeder to my two panels 20+ feet away. The 600A distribution panel parts are in stock and only have lead times of 6-12weeks. Looking through the NEC this looks code compliant to me, but I am trying to figure out of I need to be withing 10FT of the transformer on the secondary side.

2- Provide a 1200A disconnect within 10FT of the secondary side of the switch gear and feed a wire trough that I can tap as needed. The 1200A disconnect has a lead time of 8-16weeks. Each tap would have a MCB panel. This also looks code compliant to me.

Does anyone see anything wrong with these two solutions or have better recommendations?
 
Hello Augie,

I have never seen those acronyms and couldn't find a clear definition on google., but I am assuming that its not a POCO transformer.

To add a little more detail there is 5000A main switchgear in the building and we are providing a step-up transformer to feed our new 1200A switchgear that will power multiple 277/480V panels throughout the building.
 
FYI: POCO Power Company .. ie: Utility Service.
From youe second post it appears this a customer transformer supplied by their service equipnwbr thus Separate Derived System in which case the 240.21(C) rules apply. If the transformer is located inside you might look at 240l.21(C)(6), 25 ft rule;; or IF the transformer is outside 240.21(C)(5), unlimited length.
 
In general there is no issue with having multiple transformer secondary conductors sets. You will need to comply with the transformer secondary conductors rules in 240.21(C) and if transformer secondary protection is required, 450.3 (B). Remember where there are multiple sets and transformer secondary protection is required, the sum of the OCPD values cannot exceed that of a single device. Also keep in mind 408.36.
 
electrofelon said:
In general there is no issue with having multiple transformer secondary conductors sets. You will need to comply with the transformer secondary conductors rules in 240.21(C) and if transformer secondary protection is required, 450.3 (B). Remember where there are multiple sets and transformer secondary protection is required, the sum of the OCPD values cannot exceed that of a single device. Also keep in mind 408.36.
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Appreciate all the code sections!

How about option 2? Looking at the code if I have a 1200A disconnect on the secondary side then I can feed a wire trough. I am discussing this design with a fellow engineer and he is saying I am technically taping a tap if I am tapping my feeders on the secondary side of a transformer.
 
If I'm following correctly.
Your tapping a feeder from the 1200 amp to feed the panels. The 1200 is the first disconnecting means with an OCPD fed from the transformer.
If correct, your not taping a tap.
 
Dengineer said:
Appreciate all the code sections!

How about option 2? Looking at the code if I have a 1200A disconnect on the secondary side then I can feed a wire trough. I am discussing this design with a fellow engineer and he is saying I am technically taping a tap if I am tapping my feeders on the secondary side of a transformer.
Click to expand...
If your connections are on the load side of an OCPD, you are not taping a tap, but those connections will be taps unless they have an ampacity equal to the rating of the OCPD.
 
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