ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Violation?
by renosteinke - 01/27/23 09:52 PM
Does NEC 551.71 (F) apply to dwellings?
by BigB - 01/20/23 10:46 AM
Power submeter connections
by HotLine1 - 01/19/23 09:09 AM
AFDD's coming to the UK
by Texas_Ranger - 01/17/23 07:22 PM
New in the Gallery:
Burger King crown sillyness
Burger King crown sillyness
by wa2ise, December 11
240/208 to a house
240/208 to a house
by wa2ise, October 9
Who's Online Now
0 members (), 25 guests, and 10 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#89971 10/26/04 08:48 AM
Joined: Sep 2004
Posts: 86
N
Member
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

Stay up to Code with the Latest NEC:


2020 NEC & Related Reference & Study Guides
2020 NEC & Related Reference & Study Guides
Pass Your Exam the FIRST TIME with these Exam Prep Combos:
 

>> Master Electrician Exam Prep     >> JourneyMan Electrician Exam Prep
 

#89972 10/26/04 09:30 AM
Joined: Sep 2003
Posts: 650
W
Member
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


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC Now Available!
 
* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
The Watt Doctor
The Watt Doctor
Humble, TX
Posts: 440
Joined: December 2001
Top Posters(30 Days)
BigB 9
triple 3
Popular Topics(Views)
302,528 Are you busy
231,897 Re: Forum
216,532 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5