Transformer feeder

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domeng

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Does the NEC require a single protection device for the feeders from a transformer to a power panel (not a panelboard) ?The transformer and power panel are adjacent to each other and feeder is less than 10'.
 
In general, the conductors supplied from the secondary of a transformer are considered tap conductors. You will need to follow the requirements of 240.21(C).
One of the general requirements is that the secondary conductors are landed on an overcurrent device.
 
also take a look at 240.4(F) which basically breaks the transformers into two types.
 
240.21(C)(2) would cover this application and prior to the 2008 code would have permitted you to use a power panel without a main. The changes in Article 408 for the 2005 code require that the power panel have a main or line side OCPD.
 
don_resqcapt19 said:
240.21(C)(2) would cover this application and prior to the 2008 code would have permitted you to use a power panel without a main. The changes in Article 408 for the 2005 code require that the power panel have a main or line side OCPD.
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Don,
That pretty much negates the "2 wire secondary" rule in 240.4(F)..doesn't it ? Too late for a "change", but a FPN at 240 would be nice.
Another "learned something day" for me.:)
 
Gus,
The exception to 408.36(B) permits the transformer primary OCPD to protect the panel when the primary OCPD is installed per 240.21(C)(1).
 
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