is ocpd needed?

[4thgensparky]

ok here is the flow of equipment
-35kv-208/120v transformer feeds,
-1200a, 208/120 auto transfer switch which feeds
-600a main circuit breaker panel "a"
- and 600a main circuit breaker panel "b"
this is per the EE's scope of work. my question is that it seems there should be ocpd before or after the ats. any advice will be great.

 

[charlie b]

I agree with you. There is an OCPD (two of them, actually) after the ATS. The main breakers on the two panelboards will serve that purpose. If the transformer secondary conductors were run directly to the two panels, and if they were properly sized, this would be acceptable. But I think that the first component after the transformer cannot be an ATS. The way I read 240.21(C)(2)(3), if you did not put an OCPD right at the transformer secondary, then the secondary conductors must be in a raceway that extends from the transformer to a switchboard, a panelboard, or a "control device." I do not believe that an ATS counts as a "control device," in this context.

 

[qcroanoke]

I agree with you. There is an OCPD (two of them, actually) after the ATS. The main breakers on the two panelboards will serve that purpose. If the transformer secondary conductors were run directly to the two panels, and if they were properly sized, this would be acceptable. But I think that the first component after the transformer cannot be an ATS. The way I read 240.21(C)(2)(3), if you did not put an OCPD right at the transformer secondary, then the secondary conductors must be in a raceway that extends from the transformer to a switchboard, a panelboard, or a "control device." I do not believe that an ATS counts as a "control device," in this context.

What if the ATS were service rated? Wouldn't that be acceptable?

 

[malachi constant]

What if the ATS were service rated? Wouldn't that be acceptable?

Isn't a service rated transfer switch essentially a transfer switch with an OCPD in front of it? I assume based on the OP that this does not have an OCPD in front of it, and that it's not a service rated switch.

 

[qcroanoke]

Isn't a service rated transfer switch essentially a transfer switch with an OCPD in front of it? I assume based on the OP that this does not have an OCPD in front of it, and that it's not a service rated switch.

No, the ocpd would be in the ATS.

 

[skeshesh]

I agree with Charlie on 240.21(C)(2).

You also cant use 240.21(C)(6) since condition (2) is not met: "the secondary conductors terminate in a single circuit breaker or set of fuses that limit the load current to not more than the conductor ampacity..."

I do wonder, however, about 240.21(C)(3) since it does not mention anything requiring termination in specific enclosures or overcurrent protective devices. I'm also unsure about the definition of "industrial installation" - is this term referenced in the IBC or some other standard?

I agree with the OP that ocpd is required. A service rated ATS would be acceptable IMO.