NEC 2011, 240.21(C)(6)

[rayp1]

For secondary lengths longer than 25 feet what are the risk or hazards associated with this scenario? Some lengths found are up to 700 feet, but are not accessible to the public and on site there is 24/7 maintenance staff.

 

[Smart $]

For secondary lengths longer than 25 feet what are the risk or hazards associated with this scenario? Some lengths found are up to 700 feet, but are not accessible to the public and on site there is 24/7 maintenance staff.

The risks and hazards are no different than when limited to 25'. However, the probability of an undesired event will be factored by the multiple of that distance... perhaps a bit more if we consider the less obvious, such as line of sight, communicability, structural changes, etc.

Even in a supervised industrial installation you are limited to 100' for compliance.

PS: Welcome to the forum :thumbsup:

 

[rayp1]

Thank you for the reply.

1. What are these risk or hazards?

2. Do you have a code reference for the 100 feet you mention in Industrial applications?

Thank you.

 

[Smart $]

Thank you for the reply.

1. What are these risk or hazards?

2. Do you have a code reference for the 100 feet you mention in Industrial applications?

Thank you.

First, I have to assume we are discussing transformer secondaries which are considered not protected by the primary ocpd [see 240.21(C)(1)]. As such, the fault current will not even go through the secondary ocpd and the primary ocpd may not trip because the event power may be distributed through all the primary conductors (will explain more if necessary). The risks and hazards are any associated with an uncontrolled fault condition.

For supervised industrial installations, see 240.92 in general, then likely (C) or (D) for the scenario we are discussing.

 

[rayp1]

Perfect, thank you.

 

[cadpoint]

Google can also be your friend here.


Welcome to the Forum!