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#104254 - 01/20/03 05:40 AM Loose Connections!  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
[Linked Image]

Spin the barrel!

Loose connections, and improper use of equipment could be cited here!


Joe Tedesco, NEC Consultant

2017 / 2014 NEC & Related Books and Study Guides

#104255 - 01/20/03 09:46 AM Re: Loose Connections!  
Redsy  Offline
Member
Joined: Mar 2001
Posts: 2,056
Bucks County PA
What's the voltage?
The remaining KO rings should be supplemented by a bonding bushing if it is over 250 volts to ground. (per 250.97)
It would be a good idea at any voltage.


#104256 - 01/20/03 05:43 PM Re: Loose Connections!  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
Another case of a "bad connection/contact"
Probably started at the load lug. Second guess is metal fatigue at the load side fuse clips, causing 'heating scenario.
Solution, new disconnect, fuses, and possibly replace the load wiring. That is: after determining the load info. BTW: 480 volt???
John


John

#104257 - 01/20/03 08:36 PM Re: Loose Connections!  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Don’t forget that it might be 600V at the right latitude.

Suppose an AC "millivolt-drop" test on Aø with a power-rated voltmeter would be guaranteed off scale here.

It's worth noting that plastic and rubber cable insulation gets rock hard {or turns into conductive carbon} with any significant time in this condition.


[This message has been edited by Bjarney (edited 01-20-2003).]


#104258 - 01/20/03 08:45 PM Re: Loose Connections!  
jdevlin  Offline
Member
Joined: Aug 2002
Posts: 402
welland ontario canada
Why does the center fuse look too short? It is only half in the bottom clip. Is it the wrong fuse?
Could that be what happened to the fuse on the left? It looks like the same type.

[This message has been edited by jdevlin (edited 01-20-2003).]


#104259 - 01/20/03 09:57 PM Re: Loose Connections!  
Bjarney  Offline
Moderator
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
jdev — The center fuse has a universal "rejection" notch included with all NEC/UL class-R ferrule fuses. These days, it's just about impossible to find replacement fuses without that feature, and class-R fuses are, in most all cases, considered an acceptable replacement for class-H and class-K fuses.


#104260 - 01/21/03 10:52 AM Re: Loose Connections!  
jdevlin  Offline
Member
Joined: Aug 2002
Posts: 402
welland ontario canada
I see the notch now. I don't work with that type of fuse. It is new to me.


#104261 - 01/21/03 12:10 PM Re: Loose Connections!  
cubby964  Offline
Member
Joined: Oct 2002
Posts: 67
USA
Had this happen in a 400 amp disconnect on a 208 volt service to a 7-11 (convenience store). The fuse clip, wire lug, and about two inches of 500 kcmil copper all melted into a puddle in the bottom of the can, along with a pile of sand. The fusible element was 100% intact.


#104262 - 01/21/03 08:23 PM Re: Loose Connections!  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
Cubby:
Sounds like a fuse fail at the link to ferrule joint/connection. Gets hot as hell from the arcing (internal) heats the spring clips, deteriorates them eventually, then the wire/lug heat & deteriorate and poof...a meltdown.
An IR scanner (cheap ones available now) shows most hot spots, and is a good investment isf you can get the clients to do it.

BTW, Bussman may be interested in the "failed" fuse if you have it. I have a Bussman Fuseologist around here, and he loves to get burnouts for his lab.
John


John

#104263 - 01/22/03 09:33 AM Re: Loose Connections!  
SvenNYC  Offline
Member
Joined: Aug 2002
Posts: 1,691
New York City
Quote
The center fuse has a universal "rejection" notch


What's the rejection notch for? How's it supposed to work? Do some fuse holders have some sort of protrusion that's supposed to fit into these things?


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