xformer question

[spearxspark]

I am trying to find out if you can,by code come off the secondary side of a transformer twice to feed two 100A panels.The xfmr will be located outside two temporary construction trailers. Xfrmr is 75 kva 480/240 3 ph. Secondary wiring will be in rmc.Panels are 100A single ph 120/240 panels to be used for temporary power to the work trailers, lights /receptacles/air and or heat. I would like to use lugs designed for parallel wiring to come off the secondary side of the xfrmr and run one pipe to each panel. Is this acceptable by code? I have not been able to locate this in my nec handbook. Any input would be great.

 

[earlydean]

Re: xformer question

Yes, check out 240.21(C)(4) for the details. Then check out 450.3(B) for the primary OC protection.

 

[spearxspark]

Re: xformer question

Thank you early, i had previously read the mentioned code articles. My question was really about coming off the secondary twice, and if that in fact violated any codes or required additional o/c precautions. I was leaning towards it being ok, butit never hurts to get a second opinion. Thanks for your time

 

[steve66]

Re: xformer question

See also Note #2 to table 450.3(B). The handbook has diagrams illustrating this for over 600V, and also notes that it applies for less than 600V.

But this seems to indicate that the panels have to be grouped. Where is the service point where the utility stops?


Steve

 

[lady sparks lover]

Re: xformer question

Originally posted by spearxspark:
Is this acceptable by code? I have not been able to locate this in my nec handbook. Any input would be great.

Yes, done this many times!

 

[charlie]

Re: xformer question

Of course the 2005 NEC is not here yet but this has always been intended. To make it more clear, CMP-10 has made the following change to the 2005 NEC:

Panel Meeting Action: Accept in Principle

Revise existing 240.21(C) to read as follows:
"Each set of conductors feeding separate loads shall be permitted to be connected to a transformer secondary, without overcurrent protection at the secondary, as specified in 240.21(C)(1) through (6)."

This will permit any number of taps from the secondary of a transformer whether it is inside or outside. Remember that the transformer is to be protected in accordance with Article 450 and the transformer secondaries are to be protected in accordance with Article 240.