The Electrical Contractor Network

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

Books, Tools and Test Equipment for Electrical and Construction Trades

Topic Options
Rate This Topic
#110856 - 07/14/06 06:33 PM Screws in Buss
Webmaster Offline

Administrator
Member

Registered: 10/07/00
Posts: 3142
Loc: NY, USA
 Quote:
I have plenty of fire damaged equipment pictures but, they are rather bland and repetitious. They are only so much charred wire and breakers. However, this particular one is of interest because of the unique way the disconnect was connected to the circuit breaker panel.

The fault current returned on the white wires which were bonded in the disconnect.

Alan Nadon





Top
2014 / 2011 NEC & Related Books and Study Guides
#110857 - 07/14/06 07:26 PM Re: Screws in Buss
ShockMe77 Offline
Member

Registered: 06/11/05
Posts: 823
Loc: Rahway, New Jersey
Wow.

It's not as if a double pole 30 amp Sq D circuit breaker is is impossible to find and install.

It looks like it took more work to thread those screw holes than it would have to make a proper install.

Top
#110858 - 07/14/06 09:04 PM Re: Screws in Buss
Dave T Offline
Member

Registered: 01/22/05
Posts: 157
Loc: Waukesha, WI, USA
ShockMe77,
I agree but then there would have been no challenge. Just think of the thought that went into this. I bet the guy was proud of the way he solved his problem. Give the guy some credit for being an original thinker.
It would be interesting to know how many people have lost their lives because of such installations and how many have been just plain lucky that similar work such as this hasn't failed......yet.

Top
#110859 - 07/15/06 09:16 AM Re: Screws in Buss
CaOperator Offline
Member

Registered: 04/17/03
Posts: 56
Loc: Los Angeles, CA, USA
I sure would not have wanted to be the one to close in that disconnect when it shorted. Guy must have jumped 20 feet straight back, IF he was able to let go of the handle!

Top
#110860 - 07/15/06 10:21 AM Re: Screws in Buss
John Crighton Offline
Member

Registered: 05/16/05
Posts: 172
Loc: Southern California
Two things I don't understand:

Why did the neutrals at the top of the panel burn? They don't seem to be related to the disconnect in any way, so I'm thinking they're the result of a separate incident.

Since the disco wires themselves aren't burned, I'd guess that the panel main CB tripped quickly, helped by the very short wire run to the disco. If it hadn't, this could have been a nasty fire.

But what caused the disco bar to short to the screw terminals in the first place? I suspect that the insulating parts between the bar and the knives failed and/or disintegrated due to the water damage, allowing the bar to rotate in deeper and hit the screws. If the handle has an overcenter "snap" spring, all this may actually have happened completely unattended.

I'd have to say that any disconnect that can fail in this way, regardless of damage, is of an unforgivably bad design.

Oh yeah, and the guy who screwed those wires to the buses is an idiot.

Top
#110861 - 07/16/06 09:09 AM Re: Screws in Buss
Alan Nadon Offline
Member

Registered: 03/10/05
Posts: 398
Loc: Elkhart, IN. USA
It has been some years since i took these pictures but, if I rememeber right the neutrals burned because it was bonded at the disconnect and acted as the fault path to the CB panel. The rusted ground bar at the panel made a high resistance fault which heated the wires before the main tripped.
Pressboard insulators on the movable jaws and switch arm fell apart due to the water.
The screws at the panel is what made this a memorable installation.
Alan--
_________________________
Alan--
If it was easy, anyone could do it.

Top



ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals