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#104254 - 01/20/03 01:40 AM Loose Connections!
Joe Tedesco Offline
Member
Registered: 10/07/00
Posts: 2749
Loc: Boston, Massachusetts USA


Spin the barrel!

Loose connections, and improper use of equipment could be cited here!
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Joe Tedesco, NEC Consultant
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#104255 - 01/20/03 05:46 AM Re: Loose Connections!
Redsy Offline
Member
Registered: 03/28/01
Posts: 2056
Loc: 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.
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#104256 - 01/20/03 01:43 PM Re: Loose Connections!
HotLine1 Offline


Member
Registered: 04/03/02
Posts: 6776
Loc: 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
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#104257 - 01/20/03 04:36 PM Re: Loose Connections!
Bjarney Offline
Moderator
Registered: 04/10/02
Posts: 2527
Loc: 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).]
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#104258 - 01/20/03 04:45 PM Re: Loose Connections!
jdevlin Offline
Member
Registered: 08/07/02
Posts: 402
Loc: 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).]
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#104259 - 01/20/03 05:57 PM Re: Loose Connections!
Bjarney Offline
Moderator
Registered: 04/10/02
Posts: 2527
Loc: 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.
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#104260 - 01/21/03 06:52 AM Re: Loose Connections!
jdevlin Offline
Member
Registered: 08/07/02
Posts: 402
Loc: welland ontario canada
I see the notch now. I don't work with that type of fuse. It is new to me.
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#104261 - 01/21/03 08:10 AM Re: Loose Connections!
cubby964 Offline
Member
Registered: 10/18/02
Posts: 67
Loc: 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.
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#104262 - 01/21/03 04:23 PM Re: Loose Connections!
HotLine1 Offline


Member
Registered: 04/03/02
Posts: 6776
Loc: 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
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John
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#104263 - 01/22/03 05:33 AM Re: Loose Connections!
SvenNYC Offline
Member
Registered: 08/19/02
Posts: 1691
Loc: 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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