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


SCCR withstand and let through, UL 508A, SB4 question

SCCR withstand and let through, UL 508A, SB4 question

SCCR withstand and let through, UL 508A, SB4 question

We have a simple circuit that consits of a line (feeder?) at 480v, and a parallel circuit, we'd call a branch, with a low SCCR.  My understanding is that SB4.4.1 does not allow you to consider the current limiting capabilities of a current limiting fuse when it's located in a branch. I've been told this by 2 separate people from UL. I think if you read SB4.4.1 you might be able to get that from the text but it certainly doesn't say it in plain terms. Can some verify that this understanding is correct? Effectively, it means that you need CL protection ahead of a CL fuse in a branch. Or in our case, truely redundant fuses.  Why have they denied the ability of a CL fuse to limit current just based on it's location in the circuit?


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!


White Paper – Your Construction ERP RFP Checklist
Selecting business software for a medium to enterprise-sized construction concern is extremely challenging in large part because most enterprise resource planning (ERP) suites originated in the world of repetitive manufacturing and are therefore a poor fit for a project and asset-centric business. However, midsize to large contractors need the predictable, auditable processes that ERP delivers. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close