×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Article 409 and Tap Rules

Article 409 and Tap Rules

Article 409 and Tap Rules

(OP)
A particular 480V Industrial Control Panel in a "Supervised Industrial Installation" is fed from a large (say 2000 kVA) transformer, without any type of OCPD on the transformer's secondary side, and without a Main CB inside the panel. Instead, the 15-foot long tapped supply conductors terminate onto two separate CB's inside the control panel.

New Article 409 for the 2005 NEC requires that either a single OCPD be located ahead of an Industrial Control Panel, or a Main CB (i.e., ONE CB) be located within the Industrial Control Panel. But 409.21 states that this protection shall be provided in accordance with 240.21 Parts I, II, and IX.

Can the reference above (to 240.21) be interpreted to mean that the Industrial Control Panel is allowed to NOT have a Main CB (Main implies ONE), nor an upstream feeder CB by satisfying one of the tap-rules of 240.21?

RE: Article 409 and Tap Rules

It would seem to me that the reference requiring the feeder to comply with the tap rules of Article 240 would mean that you would still need an OCPD in the tap conductors where they recieve their supply and/or that the feed must comply with the rules regarding termination in a single Main as well as lenght and physical protection limitations.

RE: Article 409 and Tap Rules

(OP)
What I want to focus in on is the point you made regarding the "single Main" inside the Control Panel. Let's assume that 240.21(C)(3) is satisfied, including the requirement that the OCPD's are "grouped" (i.e., there is no single MCB; but two branch CB's that the supply conductors terminate onto instead). Then it seems that all of 240 is now satisfied. But there is still the nagging 409.21(B) OCPD Location statements that there be a single OCPD ahead of the panel or a MCB (i.e.,  one) within the panel.

RE: Article 409 and Tap Rules

I think it's a problem, but in the end, the only opinion that matters is the AHJ.  

If you're in NEC-land, you also may need UL labeling of the control panel, and I think that will require a single main device.  

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources