ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals

ECN Shout Chat
Top Posters(30 Days)
Admin 19
Recent Posts
fuse rejectors
by NORCAL. 03/29/17 01:44 AM
Old decora style outlets
by NORCAL. 03/29/17 01:41 AM
NFPA stuff
by gfretwell. 03/28/17 08:08 PM
Anyone hiring inspectors?
by HotLine1. 03/27/17 08:03 AM
ESA Arc flash course
by TheShockDoctors. 03/24/17 10:15 AM
New in the Gallery:
SE cable question
Popular Topics(Views)
231,878 Are you busy
166,758 Re: Forum
160,875 Need opinion
Who's Online Now
0 registered members (), 88 guests, and 10 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#89971 - 10/26/04 09:48 AM Using a sub feed lug  
Norstarr  Offline
Member
Joined: Sep 2004
Posts: 86
Wi
Have a 100 amp main breaker panel in a residence. Have to add a sub panel and plan to feed it with #4's and use a sub feed lug instead of a breaker. The sub panel is then protected by the 100 amp main breaker. Any code violation here?
Ron


2017 / 2014 NEC & Related Books and Study Guides

#89972 - 10/26/04 10:30 AM Re: Using a sub feed lug  
winnie  Offline
Member
Joined: Sep 2003
Posts: 649
boston, ma
I would double check the stab ratings on the main panel that is feeding the sub. Some panels limit the maximum current ratings of loads connected to a single bus stab.

Also the use of #4s falls right onto an ugly bit of NEC 310.15(B)(6). #4Cu is permitted to be protected with a 100A OCPD when it is used to supply the _main_ power feed of a single residence. #4Cu does not have sufficient ampacity to be protected at 100A _in general_, but for the specific load described in 310.15(B)(6) it is permitted to do so. This means that #4Cu is _not_ sufficient for the feed to a 100A subpanel.

But there is yet another exception, which is that the feed to any subpanel in a residence is not required to be larger than the main feed. So I think that using the #4Cu as you describe will be okay until such time as the main service is upgraded, at which point you will need to protect the subpanel at less than 100A.

-Jon



Member Spotlight
Joe Tedesco
Joe Tedesco
Boston, Massachusetts USA
Posts: 2,749
Joined: October 2000
Show All Member Profiles 
Featured:

2017 NEC and Related
2017 NEC
Now Available!

Shout Box
Powered by UBB.threads™ PHP Forum Software 7.6.0
Page Time: 0.014s Queries: 14 (0.003s) Memory: 0.7417 MB (Peak: 0.8571 MB) Zlib enabled. Server Time: 2017-03-30 16:32:10 UTC