Maybe I'm Just Being Cute...

[bcorps]

We know that an outside transformer can have its secondary protected by the OCPD it's feeding, by virtue of being outside.

But the way I read it, it's the conductors being protected, with the transformer secondary itself really being protected by the primary OCPD.

Which got me thinking in my normal kibitzing way....

If I run the secondary conductors below slab from an inside transformer to....wherever, really....can I skip the OCPD at the transformer secondary? I mean, under the slab is just about as "outside" as you can get.

 

[GoldDigger]

For tap rule purposes and service conductor purposes, under the slab (if thick enough) is considered outside the building.
But for an inside transformer, it seems to me that there would have to be some conductor length that is not under the slab, since you have to connect to the transformer.

 

[don_resqcapt19]

We know that an outside transformer can have its secondary protected by the OCPD it's feeding, by virtue of being outside.

But the way I read it, it's the conductors being protected, with the transformer secondary itself really being protected by the primary OCPD.

Which got me thinking in my normal kibitzing way....

If I run the secondary conductors below slab from an inside transformer to....wherever, really....can I skip the OCPD at the transformer secondary? I mean, under the slab is just about as "outside" as you can get.

If the transformer itself is outside, then you may be able to do that. It would be up to the AHJ, as the rule in 230.6 does not apply outside of Article 230, unless specifically referenced by a section in another article.

 

[xformer]

We know that an outside transformer can have its secondary protected by the OCPD it's feeding, by virtue of being outside.

But the way I read it, it's the conductors being protected, with the transformer secondary itself really being protected by the primary OCPD.

Which got me thinking in my normal kibitzing way....

If I run the secondary conductors below slab from an inside transformer to....wherever, really....can I skip the OCPD at the transformer secondary? I mean, under the slab is just about as "outside" as you can get.

The Primary OCPD does not protect the Secondary conductors except for two cases.

 

[don_resqcapt19]

The Primary OCPD does not protect the Secondary conductors except for two cases.

But 240.21(C)(4) permits outside transformer conductors of unlimited length prior the hitting the OCPD.