Parallel a disconnect off a transformer

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hernandez.vince1

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Chatsworth, ca
I need to connect a trash compactor that's 480 volts. The closest 480 is feeding a 75kva transformer. Can I parallel off the feed for the transformer? What is the code that references this situation in the nec?
 
It may be possible to parallel (splice or tap) off the transformer feed. Depends on load, conductor and equipment ratings. You did not provide any.
 
hernandez.vince1 said:
I need to connect a trash compactor that's 480 volts. The closest 480 is feeding a 75kva transformer. Can I parallel off the feed for the transformer? What is the code that references this situation in the nec?
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of course you can.

whether it will work or meet code requirements is another issue.

there is no specific single code provision that covers this situation. you have to figure out whether when you are done if the end result meets all the code requirements and actually works.
 
Smart $ said:
It may be possible to parallel (splice or tap) off the transformer feed. Depends on load, conductor and equipment ratings. You did not provide any.
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The conductors feeding the Xfmr are 1/o. The trash compactor is being relocated from an existing site. There its being fed with 3 # 12's, Which feed the control panel for the compactor.
 
hernandez.vince1 said:
The conductors feeding the Xfmr are 1/o. The trash compactor is being relocated from an existing site. There its being fed with 3 # 12's, Which feed the control panel for the compactor.
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I realize it seems like it should be simple... but to be completely compliant requires due diligence and makes it a lot more complex determination. In the end, it could prove to be simple, but until you jump through all the hoops, you'll not know for certain.

I'm not sure what you mean by being relocated from an existing site. The only thing that matters is whether it was powered by the same 480V system the transformer is powered by. If so, that would exclude having to perform a capacity determination of the 480V system (i.e. load calc', and equipment, OCPD, and conductor ratings ahead of the transformer OCPD).

Here's a brief list of issues that come to mind:
  • Adding or just relocating load on 480V system (mentioned above)
  • Transformer rating (kVA)
  • Transformer primary conductor rating (just size isn't enough)
  • Transformer primary OCPD rating
  • Transformer secondary OCPD rating(s), if any
  • Load served by transformer or other parameters which establish the primary conductors and OCPD would not be underrated with the added load, if not already covered by the preceding.

If all okay, then you have to deal with the tap conductor and OCPD ratings requirements to power the compactor...
 
As others noted, the devil is in the details....
Generic answer would be in most cases you can install a tap from an existing feeder/branch circuit to supply another circuit.
Making the tap in a Code compliant manner is another issue.
If your tap method is acceptable, if the existing circuit will handle to added load and if you comply with the 240.21 tap rules it can be accomplished.
 
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