Square D QO load centers

Status
Not open for further replies.
J

jordan0316

Member
Location
Broward County, FL
Has anyone heard of any issues with Square D QO load centers? A few times when opening up a QO panel I have noticed an arcing sound and smelled burning. I checked the breakers to make sure they were seated correctly, they were but when I pressed on the breaker I could hear the arcing again. :?
 
Welcome to the Forum.

The SqD QO line is a good stable line of hardware. Given the QO history of reliability, that helps, to hint at what to look for first. The symptom you describe seems like a failing connection. Dispassionately examine each splice and termination of branch circuit wiring to the breakers and terminal bars.

You're hearing it and smelling it. . . an excellent lead to localizing it. Don't forget to examine each neutral connection.

If no joy on the branch circuits, examine the Line conductor terminations.
 
Everybody has there issues even Sq D.
Sounds like you should check to see if the breaker is seating on the buss bar properly (is it arcing there? or is the contacts within the breaker beginning to fail and arcing occurring there?)
Do you see insulation on the wire attaching to the terminal on breaker burnt?
 
Square D QO load centers

Did service calls for a little while and I saw a lot of what your describing with QO.
I saw more problems with older QO than older FPE believe in or not.
I think QO is the most overrated. I would use cutler hammer or Siemens before QO. But I respect it because you see it all over the place.
JMO.


Sent from my iPhone using Tapatalk
 
Last edited:
Any type of panel can be damaged by arcing if someone plugs circuit breakers on or off the busbars while they are on and there's a load connected. (And that sort of damage can be compounded over the years if left in place such that tiny arcs continue to damage the panel, or if breakers are used and jostled a lot.) Maybe you're just noticing it more with QO because on average they are older. Or maybe the QO busbar design makes it more prone to breakers popping off accidentally; I could maybe agree with that but I'm not sure. Or maybe it's just random that you haven't noticed it with other old panels.

(As for Pizza's comparison with FPE, I don't think the problem with FPE was the stab design. It was that the breakers didn't trip when they should.)
 
al hildenbrand said:
Welcome to the Forum.

The SqD QO line is a good stable line of hardware. Given the QO history of reliability, that helps, to hint at what to look for first. The symptom you describe seems like a failing connection. Dispassionately examine each splice and termination of branch circuit wiring to the breakers and terminal bars.

You're hearing it and smelling it. . . an excellent lead to localizing it. Don't forget to examine each neutral connection.

If no joy on the branch circuits, examine the Line conductor terminations.
Click to expand...

First time I noticed it was very obvious it was coming from the connection to the buss. Tried reseating the breaker and no luck, just arcing every time I pushed on it. At that point I replaced the breaker and got the same result. I did some rearranging and replaced the breaker with yet another new one (supply house is going to take them back under warranty anyway) and the issue went away.

The most recent time I noticed it I was going to make corrections from an inspection. Someone decided they weren't going to install any romex connectors and they were going to put all the lock nuts on upside down. I open up the panel and there is the arcing sound and smell once again. This time I did the same thing, pushed on each breaker but I couldn't get it to duplicate this time. I checked all the wires very well, as I had to remove EVERY circuit to flip the locknuts and install romex connectors. when I put everything back together I still couldn't duplicate it... maybe I fixed the connection issue on that one.

I know everyone puts a lot of faith in Square D, but I just want to make sure what I am installing is safe.... I wasn't in the business (or even out of diapers) when FPE was popular, but I'm sure the same conversations were had about those panels.
 
jordan0316 said:
Tried reseating the breaker and no luck, just arcing every time I pushed on it. At that point I replaced the breaker and got the same result. I did some rearranging and replaced the breaker with yet another new one (supply house is going to take them back under warranty anyway) and the issue went away.
Click to expand...

Bare in mind, this loose connection arcing tends to be a micro arc. The arc, even that tiny, is extremely hot and will vaporize the metal on either side of it, creating pits and oxides. The pits distort the contact surface and reduce the surface area in contact shared by the bus and the breaker clips increasing the resistance in their connection. The oxides of the metals of the bus and the breaker clips also increases the overall resistance of the contact.

The increased resistance results in greater heating as load current flows, which results in greater thermal expansion and contraction, a relative movement that tends to lead to the re-striking of the micro arc and more metal vaporization.

You don't mention examining the metal contact areas of the breaker or the buss. Any recollection?

I have found I have to retire a particular buss tang, and in extreme cases, replace the panel.
 
al hildenbrand said:
Bare in mind, this loose connection arcing tends to be a micro arc. The arc, even that tiny, is extremely hot and will vaporize the metal on either side of it, creating pits and oxides. The pits distort the contact surface and reduce the surface area in contact shared by the bus and the breaker clips increasing the resistance in their connection. The oxides of the metals of the bus and the breaker clips also increases the overall resistance of the contact.

The increased resistance results in greater heating as load current flows, which results in greater thermal expansion and contraction, a relative movement that tends to lead to the re-striking of the micro arc and more metal vaporization.

You don't mention examining the metal contact areas of the breaker or the buss. Any recollection?

I have found I have to retire a particular buss tang, and in extreme cases, replace the panel.
Click to expand...
There was a few years in some older generation QO panels from maybe the 70's that used an aluminum bus. Those seem to be more prone to a bus to breaker connection failure. Often replacing the breaker was only a temporary fix as the bus was deteriorated at the connection point and was eventually going to work on the destruction of the new breaker.

Once the bus or breaker connection has been overheated neither one will ever work well again, this goes for all makes and models not just QO.
 
al hildenbrand said:
Bare in mind, this loose connection arcing tends to be a micro arc. The arc, even that tiny, is extremely hot and will vaporize the metal on either side of it, creating pits and oxides. The pits distort the contact surface and reduce the surface area in contact shared by the bus and the breaker clips increasing the resistance in their connection. The oxides of the metals of the bus and the breaker clips also increases the overall resistance of the contact.

The increased resistance results in greater heating as load current flows, which results in greater thermal expansion and contraction, a relative movement that tends to lead to the re-striking of the micro arc and more metal vaporization.

You don't mention examining the metal contact areas of the breaker or the buss. Any recollection?

I have found I have to retire a particular buss tang, and in extreme cases, replace the panel.
Click to expand...

On the first I did not inspect the metal contacts on the breaker(s) since I replaced it with a new breaker but I did inspect the buss, but in retrospect not as closely as I should have, I only looked for burns and/or discoloration.

On the second I did not, I tried for about 5 minutes to duplicate it but wasn't able too, So I did not know what breaker(s) to look at.

I also don't know how much damage I would have seen if it was not obvious since these were both brand new panels, the first one I was opening for the inspection the second one I was making corrections from the inspection.
 
jordan0316 said:
... Tried reseating the breaker and no luck, just arcing every time I pushed on it. ...
Click to expand...

Yeah, well, don't push on the breaker when it's on. That's not going to help things. Al gave a pretty good explanation of why.

I learned about this sort of problem a long time ago working with a damaged theatrical dimmer set. The theatrical lights were connected to the dimmers with 3-pin 'stage pin' connectors. Well at some point probably just one of these connections had some arcing. Problem is, they re-patch the connectors for every show with a different lighting design. So the arc-damaged pins on that connector presumably had a bad connection to the socket on the next dimmer they were plugged into, causing more arcing. The problem spreads like a sexually transmitted disease; bad pins get plugged into sockets, which cases small arcing damage to the sockets. The next pins plugged into that socket get damaged, and so on.

Someone had tried fixing the problem by filing the blackened metal off the pins, but this just made the problems worse with un-even surfaces.

Same thing goes for ordinary Edison plugs and outlets. If you have an arc damaged cord pin, stop using the cord. If you have an arcing breaker, replace it, and don't move it to another spot on the busbar.
 
jordan0316 said:
On the first I did not inspect the metal contacts on the breaker(s) since I replaced it with a new breaker but I did inspect the buss, but in retrospect not as closely as I should have, I only looked for burns and/or discoloration.

On the second I did not, I tried for about 5 minutes to duplicate it but wasn't able too, So I did not know what breaker(s) to look at.

I also don't know how much damage I would have seen if it was not obvious since these were both brand new panels, the first one I was opening for the inspection the second one I was making corrections from the inspection.
Click to expand...

Possible the arcing you were hearing wasn't from a bad bus connection but rather poor contact inside the breaker, or even loose load terminal.
 
Flipping the lock-nuts?
If on romex connectors what's the issue.
If on EMT or GRC as long as not used for grounding and is wrench tight again what is the issue.
 
Personally I think Cutler Hammer CH-CH is a better product than QO, the buss mounting system is similar but CH's is superior IMO.
 
kwired said:
Possible the arcing you were hearing wasn't from a bad bus connection but rather poor contact inside the breaker, or even loose load terminal.
Click to expand...

Another possibility with Sq D, maybe, is counterfeit breakers- in which case there is no telling what the fakers put (or left out:p) inside that breaker or how off (however minuscule) spec they are when jabbed in. I do concur too with Hildenbrand above about closer inspection of that bus, sometimes minor discoloration can have a way of hiding if you're not careful.
 
user 100 said:
Another possibility with Sq D, maybe, is counterfeit breakers- in which case there is no telling what the fakers put (or left out:p) inside that breaker or how off (however minuscule) spec they are when jabbed in. I do concur too with Hildenbrand above about closer inspection of that bus, sometimes minor discoloration can have a way of hiding if you're not careful.
Click to expand...
You need to expose more then just the bus position in question or you may not even notice minor discoloration. You need to pull adjacent breakers to compare. Also newer QO with more non metallic shielding over the bus can sometimes give away hot spots because there may be signs of melting of that non-metallic shielding.
 
One thing about QO breakers is that they really are "Quick Open". The other day I was working on two panels. One was a bolt-on ITE panel, the other was a QO panel. While livening up a circuit on the ITE panel there was a short. There was a small arc-flash contained mostly within the breaker, but I saw light. There was a small explosion sound. The breaker tripped.

Same scenario on the QO panel. I hadn't even gotten the handle completely closed and there was a click and the window showed orange. No flash, no explosion sound.

I felt a little embarrassed however, since both times were because there was one box I had missed down the line where they had cut the old lights down by cutting the BX whip. It was dark up in that ceiling, but there was no reason I should have missed them.
 
Status
Not open for further replies.
Top