Transformer Secondary Protection

[faresos]

If any transformer (480 delta-208/120V) located in location within the building and the secondary conductors (no exposed conductors) was ran underground let?s say for 100ft, do we still need to have an OCPD at the transformer? My understanding was since it was ran underground then it will consider to be outdoors and it only required at the stup-location within 10ft of the panelboard with MCB or OCPD. Any thoughts?

Thanks,

 

[Smart $]

Generally speaking, not if the transformer is inside. That would only be true if transformer is outside. 240.21(C)

If this is a supervised industrial facility, you may be able to. 240.92(C)

 

[don_resqcapt19]

If any transformer (480 delta-208/120V) located in location within the building and the secondary conductors (no exposed conductors) was ran underground let?s say for 100ft, do we still need to have an OCPD at the transformer? My understanding was since it was ran underground then it will consider to be outdoors and it only required at the stup-location within 10ft of the panelboard with MCB or OCPD. Any thoughts?

Thanks,

The application of 240.21(C)(4) requires that the transformer be outside of the building or structure.

 

[faresos]

Thanks all for the reply.

I must was mistaken with 230.6 which defines "Conductors Considered outside the Building" but this section seems only applies to the main service.

 

[don_resqcapt19]

Thanks all for the reply.

I must was mistaken with 230.6 which defines "Conductors Considered outside the Building" but this section seems only applies to the main service.

While you are correct that 230.6 only applies to service, it would not be unreasonable to apply that to other applications.

The issue with 240.21(C)(4) is that only the load end termination is permitted in the building. You application had the supply end of the secondary conductors in the building as that is where the transformer is located.