Page 1 of 2 12 LastLast
Results 1 to 10 of 18

Thread: Feeder Sizing

  1. #1
    Join Date
    Sep 2012
    Location
    NJ
    Posts
    2,159

    Feeder Sizing

    Have some feeders where only the switch size( in amps) is shown and the fuse size of the switch. These feeders are feeding other panels. When sizing these feeders do you go off the switch size, fuse size or panel size? I think the breaker or switch should be sized to the panel being fed, correct? Thanks,

  2. #2
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    25,862
    The designer should tell you the switch size, fuse size, feeder size and panel size. Without that info you're just guessing.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #3
    Join Date
    Sep 2012
    Location
    NJ
    Posts
    2,159
    Quote Originally Posted by infinity View Post
    The designer should tell you the switch size, fuse size, feeder size and panel size. Without that info you're just guessing.
    He does give switch, fuse and panel size. Left out feeder sizes. It's a budget and I'd like size based on what's given.

  4. #4
    Join Date
    Dec 2015
    Location
    Texas
    Posts
    170
    Quote Originally Posted by mstrlucky74 View Post
    He does give switch, fuse and panel size. Left out feeder sizes. It's a budget and I'd like size based on what's given.
    Size based upon the OCPD for the Feeder. For example, if it's a 600A rated panel, but it's fused for 450A, size the feeder to 450A. I think this is what you're asking right?

  5. #5
    Join Date
    Sep 2012
    Location
    NJ
    Posts
    2,159
    Quote Originally Posted by tw1156 View Post
    Size based upon the OCPD for the Feeder. For example, if it's a 600A rated panel, but it's fused for 450A, size the feeder to 450A. I think this is what you're asking right?
    yes it is thanks. So your saying to size based on the switches fuse and not the switch size? Why is that? Just curious, thanks.

  6. #6
    Join Date
    Dec 2015
    Location
    Texas
    Posts
    170
    Quote Originally Posted by mstrlucky74 View Post
    yes it is thanks. So your saying to size based on the switches fuse and not the switch size? Why is that? Just curious, thanks.
    The switch size only indicates the max size of the OCPD (fuse for example) that can be placed in it. Example Disconnect Frame sizes are 30, 60, 100, 200, 400, 600, but you're not required to use those same size fuses in them. You can have a 600A Frame Disconnect with 450A fuses if your load only needs to be sized for this. Just so I'm understanding your terminology, when you refer to switch, do you mean Disconnect?

  7. #7
    Join Date
    Sep 2012
    Location
    NJ
    Posts
    2,159
    Quote Originally Posted by tw1156 View Post
    The switch size only indicates the max size of the OCPD (fuse for example) that can be placed in it. Example Disconnect Frame sizes are 30, 60, 100, 200, 400, 600, but you're not required to use those same size fuses in them. You can have a 600A Frame Disconnect with 450A fuses if your load only needs to be sized for this. Just so I'm understanding your terminology, when you refer to switch, do you mean Disconnect?
    Thanks, got it. I mean fused switch in a switchboard.

  8. #8
    Join Date
    May 2018
    Location
    Boston
    Posts
    39
    I basically asked this same question and got the same answer. Here is the thread:

    http://forums.mikeholt.com/showthrea...768&highlight=

  9. #9
    Join Date
    Jul 2003
    Location
    New Jersey
    Posts
    25,862
    Quote Originally Posted by mstrlucky74 View Post
    Thanks, got it. I mean fused switch in a switchboard.
    Then use the "weakest link" for the feeder, if the switch is 200 amps but the panel or fuse size is 125 amps then the feeder needs to only be 125 amps.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  10. #10
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    16,900
    I agree. Use whatever the OCPD rating is.
    Bob

Posting Permissions

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