ATS's and the Tap Rule

[Shujinko]

Are Automatic transfer switch (ATS) conductors considered a tap coming off the load side terminals? If all the conductors on the normal, emergency, load side are the same size? I have an installation where the ATS is about 60' from the panel it feeds on the load side of the ATS. Am I required to place an OCPD near the ATS on the load side to protect the load side conductors?

 

[augie47]

The ATS should have a built-in over-current device if its service rated or an over-current device ahead of it on the utility side and an over-current device ahead of it on the generator side.
You "Load" conductors on the ATS are subject to the tap rules based on the size of those devices (largest)

 

[Shujinko]

The ATS should have a built-in over-current device if its service rated or an over-current device ahead of it on the utility side and an over-current device ahead of it on the generator side.
You "Load" conductors on the ATS are subject to the tap rules based on the size of those devices (largest)

But if my normal, emergency, and load side conductors are all the same size and the OCPDs on the normal and emergency side are sized to protect the load side conductors then I wouldn't need a OCPD on the load side conductors located downstream of the ATS load terminals? Per the definition of a tap conductor in NEC 240.2, in my situation the load side conductor isn't really a tap conductor because it is the same size as the normal/emergency conductors.

 

[jaggedben]

Are Automatic transfer switch (ATS) conductors considered a tap coming off the load side terminals? ...

Short answer: no. A transfer switch has zilch to do with the definition of a tap, which is a conductor that is not protected by the OCPD ahead of it.

 

[Smart $]

But if my normal, emergency, and load side conductors are all the same size and the OCPDs on the normal and emergency side are sized to protect the load side conductors then I wouldn't need a OCPD on the load side conductors located downstream of the ATS load terminals? Per the definition of a tap conductor in NEC 240.2, in my situation the load side conductor isn't really a tap conductor because it is the same size as the normal/emergency conductors.

Well, you really should not go by size. Conductor ampacity determines whether or not a tap situation exists.

 

[augie47]

Sounds like the tap rule does not apply.................
Tap Conductors. As used in this article, a tap conductor is defined as a conductor, other than a service conductor, that has overcurrent protection ahead of its point of supply that exceeds the value permitted for similar conductors that are protected as described elsewhere in 240.4.

 

[steve66]

But if my normal, emergency, and load side conductors are all the same size and the OCPDs on the normal and emergency side are sized to protect the load side conductors then I wouldn't need a OCPD on the load side conductors located downstream of the ATS load terminals? Per the definition of a tap conductor in NEC 240.2, in my situation the load side conductor isn't really a tap conductor because it is the same size as the normal/emergency conductors.

No, you wouldn't need an OCPD on the load side of the ATS. In fact, I would consider putting an additional OCPD on the load side of an ATS a really bad design. If that OCPD trips, the load will loose power, and the generator can't help.