User Tag List

Results 1 to 2 of 2

Thread: Explain the AS/AF, AT/AF sizes

  1. #1
    Join Date
    Aug 2011
    Location
    New York, NY
    Posts
    32
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Explain the AS/AF, AT/AF sizes

    looking to have a better understanding about trip and fuse, but it seems everything I see is under manufacturer

  2. #2
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    8,244
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by mepengineer View Post
    looking to have a better understanding about trip and fuse, but it seems everything I see is under manufacturer
    Not all mfrs are the same, that’s why. AS/AF for fused switches means Amp Switch /Amp Fuse. So for example 600AS/500AF means you have a 600A rated switch holding a 500A rated fuse. The switches come in only a certain number of switch sizes; typical for North America (NEMA KS-1 design specs) is 30, 60, 100, 200, 400, 600, 800, 1200, 1600, but not all mfrs offer all of those sizes, especially above 800A. But there are a LOT more fuse sizes than switch sizes.

    AF/AT are the same concept for Circuit Breakers, except Amp Frame / Amp Trip. Frame sizes vary a lot more from mfrs to mfr, so some have 100AF, some are 125AF, some only start at 150AF, etc. then in larger frames, some mfrs have dropped some old traditional frame sizes such as 600AF because their newer 800AF is the same physical size anyway. So bottom line, don’t get too excited about being rigid on the numbers unless future upgrade capability is of importance. So for example you need 400A now, but plan on increasing to 500A in the future. You can size the conductors for 500A and call for a 600AF/400AT Breaker, then in the future you can just change the trip unit or rating plug in that breaker to 500A. Had you used a 400AF/400AT Breaker, you would have to change out the entire breaker. You may also need to use a larger frame with a smaller trip if you have to increase the conductor size for voltage drop to a size that can’t fit in a smaller frame.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •