ECN Forum Forums General Topics of the Trade General Discussion Area Square D Breaker failure

Last week I had a service call out to a home with an inoperable circuit. After some looking and talking heres what I found.

Split level home with a 125amp Square D panel in basement.The problem circuit ran from panel straight up to living room hit 6 plugs and some lighting and then dropped back downstairs to a pullchain.

The owner took the power out of the light ran it into a singlegang box for rec then up to a switch then back to the light. All his work appeard fine and no sign of damage anywhere, I looked very closely.

The breaker to this circuit is now dead,in tripped position will not reset. Each and every plug upstairs and through the switch's main feed on to the next plug have done a melt down, things just melted to each other causing shorts everywhere. The burn did not continue to inside the sleave of the romex but was contained in the box.

This was true of every wire upstairs both the hot and the nuetral. On the downstairs wire there was no sign of damage.

My best guess at this point is the homeowner goofed and wired his plug a dirrect short. He swears he didn't and has done things like this before. He seemed somewhat competant.

This was all on a 15amp square D homeline breaker. Homeowner said when he turned it on he could hear the buzzing for some time but didn't know what it was

Heres the Q's. Why didn't it damage the wire downstairs where he would have made his mistake like it did the upstairs.

When he moved the wire maybe yanked it causing an already to tight staple to cut into the wire? Doubtfull. All wiring has been replaced. No sign of that and it was all looked at closely.

Also should a rep be notified this rings of FP breakers. Or should say UL be notified.

This is obviously a problem of a short and a major overcurrent through the wire compounded by a faulty breaker. Is it just a fluke?

Neil

[This message has been edited by Bomzin (edited 03-28-2004).]

Hey Neil!

Welcome to the forum.

You paint an interesting picture. I'm curious about the through-splices of the branch circuit. In the outlets in the living room, were the receptacles splicing the conductors together, or, were the conductors spliced with wirenuts and a pigtail?

I'm guessing that the "back stabs" on the receptacles were used, or that the terminal screws were consistantly loose, leading to "glowing connections".

Had a heavy load been put on the end of the circuit? . .something like an electric heater or a dehumidifier? The heat degradation over time of the connections behind the living room receptacles, followed by the mis-wiring of the new switch / outlet into a short circuit would result in a higher than normal resistance, strangling the short circuit current. Hence the long buzzing.

Of course, the bad breaker hypothesis is a good one. It's just that SqD, in my experience, has had such extraordinary quality, I would try to rule out any other possiblity.

It sounds to me like poor connections in the fault path, in which case the breaker may have been fine. The path could have provided enough resistance to not "pop" the breaker right away, also resulting in heat and spaterings of metal at each loose connection throughout the circuit.

As to the proper notification procedure: It would be a noble thing for you to report if indeed it was a manufacturer defect. Nothing in it for you, but the manufacturer could learn and/or take corrective action, curbing their liability and, more importantly, increasing future public saftey. All this of course if it was a bad breaker, otherwise a waste of time.

But if you did find out the quickest, easiest way to hande reporting such suspicions, either to UL or manufacturer, let us know. It'd be more likely to report such things myself if I didn't have to do the pre-research.

... I agree with Jps1006, and if possible send the offending breaker back to Square "D"'s R&D dept..Good Luck,..I'm honestly surprised that it failed...I tout Square "D" to my customers as the "Cadillac" of breakers,...well,at least the QO style anyway,...
Russ

After the rewire all lights and everything in the living room where turned on. 4.3 amp load at test.

Rec made the connection throughout the circuit.

This happend right after he did a small rewire downstairs. Although no damage was present downstairs.

All the grounds were twisted with green wire nuts. I also noted the grounding on the water pipe, 2 clamps , did not check outside service.

I have been a service man for going on 9yrs now with electronic experience before that. I always find the cause of the problem. This one has me stumped.

If the Homeowner did short it downstairs why no damage? Last point of damage was upstairs.

I took some pics will post if I can figure out how.

Neil

Also the wire going to the breaker had also done a meltdown along with neutral.

Would a loose connection at the very first point cause this with a short placed at the end of the circuit.


Neil

oops I need to work on my reading comprehension..... sorry Bomzin

[This message has been edited by sparked (edited 03-30-2004).]

At least the breaker failed in the "open circuit" condition. A safe failure. Not like FPE breakers that are known to fail in the "on" position and become stuck on passing large quantities of fault current.....

Sounds to me like the effective ground-fault current path is not so effective. Enough heat was developed to melt the insulation, but not trip the breaker. The 'buzzing' sound means the breaker was at it's very limit. For how long is anyones guess at this point. It does not seem the homeowner will give you much help in figuring this out.

Pierre

At least two things had to happen at once here.

First, a large amount of current had to have been drawn from a point at least after the last damaged receptacle and conductors. This may or may not have been more than OPD was rated for.

Second, the connections to those existing receptacles HAD to have a high resistance. This is evidenced by the burned and overheated insulation only in the vicinity of the connections. (This is exactly the same problem you see with aluminum wiring which is caused by the connections becoming loose.) A normal connection should easily carry a current equal to that of the conductor and the cable would have also faulted if enough current were drawn.

As to the breaker, you say that the wire was also burned on its screw. Question is then, did the breaker fail to open due to an excessive current condition or was there a high current draw within the rating of the breaker which caused the connections to overheat, including the terminal (which was also loose) on the breaker and THAT is what did the breaker in.

Now, a couple of things that bother me about this story. Did the extension wired by the homeowner ever work or was this problem started (and was evidenced by the breaker buzzing) when he completed his work and turned the breaker back on for the first time? If the latter then that would indicate either a problem with something he did or there was something plugged into a receptacle AFTER the last damaged receptacle that drew a lot of current when the breaker was turned back on. I suspect somebody (not you) is being less than forthcoming here.

As I said above, even if the breaker was actually bad (which I doubt), there had to be a reason for the current draw first for anything to happen and we are not hearing about that.

It would be impossible for the breaker to cause this by itself. Once we know exactly what caused the current draw, a determination can be made as to how much it was and only then we can say whether the breaker failed to trip or it was a victim of overheating itself.

-Hal