ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Top Posters(30 Days)
twh 10
Admin 4
Recent Posts
Windows 10, who's upgraded?
by ElectricianBud. 05/27/17 11:02 AM
How do you find a good employee?
by ElectricianBud. 05/27/17 10:58 AM
Recall notice: Bosch Solar panels
by ElectricianBud. 05/27/17 10:53 AM
Correct rotation, wrong sequence
by Potseal. 05/27/17 12:15 AM
Dryer, Range grounding from "Main" panel
by sparkync. 05/25/17 05:49 PM
New in the Gallery:
SE cable question
Popular Topics(Views)
236,902 Are you busy
171,910 Re: Forum
164,800 Need opinion
Who's Online Now
1 registered members (richard), 64 guests, and 9 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate This Thread
#176922 - 04/16/08 09:56 AM What caused this situation?  
Admin  Offline

Administrator
Member
Joined: Oct 2000
Posts: 3,443
NY, USA
What caused this situation?

submitted by Joe Tedesco:

[Linked Image]


Tools for Electricians:

#176923 - 04/16/08 10:42 AM Re: What caused this situation? [Re: Admin]  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Here's another picture of a situation that is constantly questioned by many everywhere!

The termination's of the EGC and Grounded (Neutral) conductor.

[Linked Image]


Joe Tedesco, NEC Consultant

#176928 - 04/16/08 12:07 PM Re: What caused this situation? [Re: Joe Tedesco]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,080
Estero,Fl,usa
(ref top pic)
A loose connection and an uncleared ground fault?
It looks like the bottom conductor wasn't inserted all the way through and missed being clamped by the screw


Greg Fretwell

#176933 - 04/16/08 12:27 PM Re: What caused this situation? [Re: gfretwell]  
SteveFehr  Offline
Member
Joined: Mar 2005
Posts: 1,206
Chesapeake, VA
The panel EGC and neutral look awfully small... And the terminal bus is rusty.

Looks also like the insulation wasn't stripped properly on that burnt wire, either- not only was it offset and the screw not properly clamping it, but might have been insulated from the screw preventing proper contact, too. Poor contact = not enough fault current to trip the breaker + excessive heating = fire.

This isn't an FPE panel, is it?


#176947 - 04/16/08 07:35 PM Re: What caused this situation? [Re: SteveFehr]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,826
Brick, NJ USA
Top pic...bad connections, two conductors under 1 screw. Result of low quality workmanship. This design of neutral/ground buss was in GE panels, and the installer had to get the conductor directly under the screw to get a decent termination. Two conductors result in deflection to the sides of the screw, resulting in a poor termination. the poor termination results in a high resistance connection, creating heat on the neutral conductor, and you have a pic of the ultimate end result. This is based on my opinion, and experience.

The second pic, IMHO is an OLD panel that has a corrosion situation. Also, it appears that the two conductors under 1 screw situation is here also.


John

#176956 - 04/16/08 11:15 PM Re: What caused this situation? [Re: HotLine1]  
WESTUPLACE  Offline
Member
Joined: Mar 2004
Posts: 251
Kingwood, TX USA
Two wires of different gauge in 1 hole. Only one tight.


#176958 - 04/17/08 12:02 AM Re: What caused this situation? [Re: WESTUPLACE]  
rhagfo  Offline
Member
Joined: Apr 2001
Posts: 43
Portland, OR. USA
Top Pic Why double lug??? Looks like there a plenty of avaiable unused terminals.


#176963 - 04/17/08 06:11 PM Re: What caused this situation? [Re: rhagfo]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,826
Brick, NJ USA
Rhagfo:
Terminating the neutral and ground conductors in one lug, or under 1 screw was a 'trade practice' in some areas. The reasoning was to keep the neutral & grd 'together' for tracing purposes. BTW, not a 'practice' that I have done, nor taught to anyone, but something the 'old-timers' passed on to the 'young guys'.



John

#176986 - 04/18/08 06:07 AM Re: What caused this situation? [Re: HotLine1]  
Elviscat  Offline
Member
Joined: Aug 2005
Posts: 214
Seattle Washington USA
I'd venture that a loose connection+neutral current on the EGC leads to a burnt/corroded connection. In times gone by it used to be common practice to put 2 neutrals under one screw, this created a definite hazard when one of the circuits is a multiwire, and the other circuit was being removed or serviced.


#176993 - 04/18/08 12:55 PM Re: What caused this situation? [Re: Elviscat]  
mikesh  Offline
Member
Joined: Jun 2006
Posts: 613
Victoria, BC, Canada
Current code would of course demand 1 neutral per terminal.
Manufacturers instruction state 1 conductor per terminal for Grounded circuit conductors. The bonding terminal however are allowed 2 #14 or 2 #12 copper or 2#12 or 2#10 aluminum under 1 screw. 1 wire per terminal for larger bonding conductors up to the largest wire permitted for the particular bonding terminal which is often #6. Larger bonding conductors can be accommodated by adding factory approved lugs to the bonding strips or to the enclosure.
I have always followed the 1 neutral 1 screw but until about 10 years ago it was as many bonding wires as would fit as long as we twisted them all together.



Member Spotlight
togol
togol
NW In. USA
Posts: 421
Joined: September 2005
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: 0.035s Queries: 15 (0.003s) Memory: 0.8113 MB (Peak: 0.9935 MB) Zlib enabled. Server Time: 2017-05-27 21:15:02 UTC