Transformer secondary conductors

[rojay]

Can anyone provide a code reference on whether or not the NEC 230.6 guidelines for service conductors considered outside of the building can be applied to transformer secondary conductors run indoors, but within a building slab?

 

[jim dungar]

Can anyone provide a code reference on whether or not the NEC 230.6 guidelines for service conductors considered outside of the building can be applied to transformer secondary conductors run indoors, but within a building slab?

Are these utility service conductors or customer owned transformer secondary conductors?

 

[rojay]

Customer owned transformer/conductors

 

[augie47]

The wording of 240.21(C)(5)(4)(c) seems to cover that. (2017)

 

[david luchini]

See 225.32

 

[jim dungar]

Customer owned transformer/conductors

Basically only the stuff connected on the utility side of the service point is subject to article 230.

 

[rojay]

See 225.32

I see your logic. If the transformer was physically located outdoors (which it isn’t) there would be no restriction on how far into the building the overcurrent device was located as long as the conductors were “outside the building “ in the slab. It’s the end part that’s says “For purposes of this section...” that makes me nervous.

 

[augie47]

I see your logic. If the transformer was physically located outdoors (which it isn’t) there would be no restriction on how far into the building the overcurrent device was located as long as the conductors were “outside the building “ in the slab. It’s the end part that’s says “For purposes of this section...” that makes me nervous.

That is a big IF. From your OP. I though the transformer was outside the building. If not, the reference I gave is likely invalid.

 

[rojay]

Yeah, it’s inside of a big warehouse.
480 distribution panel w/ 75 KVA transformer located next to it. 200 amp panel is on the opposite side of the building.

 

[tom baker]

So there is a long run of transformer secondary conductors to the 200A panel, does that panel have a ocpd on the secondary’s?

 

[rojay]

So there is a long run of transformer secondary conductors to the 200A panel, does that panel have a ocpd on the secondary’s?

There is a 200 amp main in the panel

 

[tom baker]

Got it. The transformer secondaries are protected by the primary ocpd across the warehouse. Have you reviewed Art 450? I This is not an issue I have encountered before.

 

[augie47]

Unless it is a 2 wire to 2 wire or Delta-Delta transformer (240.21(C)(1), I can't see where the install would meet any of the allowable rules in 240.21(C)

 

[Engser18]

Yeah, it’s inside of a big warehouse.
480 distribution panel w/ 75 KVA transformer located next to it. 200 amp panel is on the opposite side of the building.

You will need fuse disconnect switch, btw xformer and panel. 25 ft rule apply ( primary and secondary). If primary OCPD rated lower than primary conductors, then 25 ft apply only for secondary conductors.

 

[Llortus]

Don't know transformer details but if distribution type take a look at schematic, may already have fusing internal at least on primary.