Sq D Breaker Type

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There are some Square D panels that accept both types. If you can see the bus it has both stabs and holes.
 
All panels will accept both styles since the late 80's when the NQOD series replaced the original NQO (plug on) and NQOB (bolt on). The current version, for the past two decades, is the NQ series.
 
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The only bolt-on ones I've ever seen will also take the stab-ins. I've never seen a bolt-in only QO panel.
As Jim said, the older models was bolt in only, and those older breakers will not fit the newer NQOD panels. The newer bolt in breakers have a hump to clear the stabs, where the old style is flat and will not fit.
 
No.
All QOB breakers are fully interchangeable, their basic mounting design has never been changed.
I hate to tell you, they are not. Just looked at a job a few minutes ago that has a QOB panel. If the panel wasn’t live, I would pull the breaker to show the difference. The newer QOB breakers have a hump to clear the plug on finger, the old QOB breaker does not. I know, because I ran across that problem during a panel change out. Hard to see in the picture, but the top breaker is new style, the middle breaker is old style. I will see if I still have an old style laying around my shop, but I think I have chunked all of those. 7F07F7C8-8132-4FB5-AAEA-0009975F785B.jpeg
 
I hate to tell you, they are not. Just looked at a job a few minutes ago that has a QOB panel. If the panel wasn’t live, I would pull the breaker to show the difference. The newer QOB breakers have a hump to clear the plug on finger, the old QOB breaker does not. I know, because I ran across that problem during a panel change out. Hard to see in the picture, but the top breaker is new style, the middle breaker is old style. I will see if I still have an old style laying around my shop, but I think I have chunked all of those. View attachment 2556427
I guarantee you the breakers are interchangeable.

The pictures you show, left to right, are a single pole breaker connected to an outside bus finger (say the A phase), then there is a breaker connected to the center bus (say the B phase) via a screw style finger, finally there is a breaker connected to the opposite outside bus finger (say the C phase).

The change from these old NQOB bus fingers to the new combination style resulted in the NQOD generation.

I sold these Square D products from 1978 through 2005.
 
I guarantee you the breakers are interchangeable.

The pictures you show, left to right, are a single pole breaker connected to an outside bus finger (say the A phase), then there is a breaker connected to the center bus (say the B phase) via a screw style finger, finally there is a breaker connected to the opposite outside bus finger (say the C phase).

The change from these old NQOB bus fingers to the new combination style resulted in the NQOD generation.

I sold these Square D products from 1978 through 2005.
The new breakers are, but the old breakers will not fit the newer panels. Been there, tried that. You can force it, but it bends the breaker.
 
The new breakers are, but the old breakers will not fit the newer panels. Been there, tried that. You can force it, but it bends the breaker.
There has been no change to the breaker's bolt-on connection. At least not prior to when I retired last July.

There is no information, on any Schneider Electric site, that shows you how to identify which breakers fit into which panelboard other than the generic types QO and QOB, nor anything providing any warning about potential incompatibility.

Do you have a date when this supposed change occured?
 
When I go back to do the job, I will have to shut the power off to install a new breaker in the MDP, I will pull that one to show why it will not fit newer panels. If you look at the newer QOB breakers, you will see the breaker tab is offset, where the old ones are flat. The plug in buss is raised above the the bolt in buss so the plug in breaker stays level.
 
If you look at the newer QOB breakers, you will see the breaker tab is offset, where the old ones are flat. The plug in buss is raised above the the bolt in buss so the plug in breaker stays level.
What you are describing is how QOB breakers have always been built. The dual finger design was first introduced in the late 80s, so it has been around for some 30 years without change. Prior to that NQOB center phase bus connections were actually screw in stand offs as shown in your photo while the outer busses used relatively flat fingers. The bolt-on bus point has always had to be recessed below the plug-on jaw in order to provide clearance for the bolt-on screw while keeping the breaker face at the same plane.

A QOB breaker bus connection drawing from 2008 looks identical to a drawing from 1968.

Please provide a date you think defines old style versus new style, and I will be glad to research it.
 
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Here is a picture of the panel at my house, it is a NQOD. Note the bump on the buss. Notice the offset on the QOB, and where the QO lines up. I dug through my old breakers ( surprised at how many FPE I had) and didn’t find one, but the original QOB had two pieces metal bent and folded to make the bolt on tab. 35A5A733-BF3F-4498-AA8C-60FFC1A56495.jpegD32610EB-479D-4495-81D0-9980955B2657.jpeg
 
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