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Panel to Jbox conversion found when trouble shooting open neutral. #103700
10/29/02 08:36 PM
10/29/02 08:36 PM
Joe Tedesco  Offline OP
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Panel to Jbox conversion found when trouble shooting open neutral.

[Linked Image]
[Linked Image]

Photo's by Tom Horne

Joe Tedesco, NEC Consultant
2017 / 2014 NEC & Related Books and Study Guides
Re: Panel to Jbox conversion found when trouble shooting open neutral. #103701
10/30/02 03:54 PM
10/30/02 03:54 PM
mamills  Offline
Joined: Nov 2001
Posts: 745
Wharton, Texas, USA
Judging by the long and narrow dimensions of this box, it looks like this was home to a SqD XO frame or an ITE pushmatic breaker frame at one time...

Do the circuits in this Jbox terminate in the panel to the left through the single large MC raceway (a wire-fill issue here)? Are there multiple neutrals pulled through the same raceway and landed with the existing neutrals on the same buss (double-lugged)? Did the open neutral occur in this Jbox?

Is there a cover of some sort for this Jbox (possibly removed for the pic or during servicing)?

Mike (mamills)

Re: Panel to Jbox conversion found when trouble shooting open neutral. #103702
10/30/02 07:00 PM
10/30/02 07:00 PM
tdhorne  Offline
Joined: Mar 2001
Posts: 345
Maryland, USA
I found this panel cabinet to junction box conversion while trouble shooting an open neutral on a branch circuit.

The cover was removed to permit access for trouble shooting and photography. Circuits in this cabinet originate in a lighting and appliance panelboard on the floor above. The cabinet to the left is another converted panel. There is no connection between the two. The open neutral occurred on the buss bar in this cabinet that was used to terminate all of the neutral conductors from the Panel on the floor above as well as all of the existing branch circuit neutrals. When the geniuses that did that work ran out of holes they simply doubled up. Strangely enough it was one of the single terminations that went bad.

All I have done so far is to re tighten all of the connections and order terminal strips that have sems pressure washers under each screw. I plan to terminate all of the conductors in circuit numerical order on the terminal strips. I will have to ring out and tag the multi wire branch circuits that run through this cabinet in order to avoid a repeat of a previous problem.

The tenant that occupied this space before brought in someone to install an additional panel powered from a feeder supplied from the panel that used to be to the left of this one. In order to free up two slots for the feeder breaker this "morrune" added replacement only tandem breakers to that panel. In the process he managed to disarrange a multi wire branch circuit so that all three ungrounded conductors were on the same phase. Since this was the main lighting circuit for a gymnasium the circuits neutral ended up carrying forty eight amps. Even XHHN 12 gauge will not put up with that. If the failure had not taken an ungrounded conductor with it we would have been unaware of it for a long time. Because the affected circuit had been run in EMT by real electricians their careful work was carrying the neutral current all the way back to the service equipment bonding jumper and thence home to the X0 of the transformer set.

[This message has been edited by tdhorne (edited 10-30-2002).]

Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use" Thomas Alva Edison


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