QO breaker Question- tab extension on hold-down?

Status
Not open for further replies.
Just guessing: something related to 'Circuit Total Limiting' breakers that restrict 'skinny' breakers to a subset of panel locations.

-Jon
 
winnie said:
Just guessing: something related to 'Circuit Total Limiting' breakers that restrict 'skinny' breakers to a subset of panel locations.

-Jon
Click to expand...
Don't think so.

Every time I have seen it was on two pole non tandem's like OP posted. Also was always on breakers likely manufactured before I was even born or at least was very young, and before CTL became a thing.

They don't plug into any panels made since they went away with the metallic foot rail that I have seen, they don't plug into many the so called newer metal rail panels (that are at least 30-35 years old now) either though.
 
It's a device to keep you from putting a tandem in certain slots. This stems from the days where there was a limit on 42 poles in the panel.
 
rnatalie said:
It's a device to keep you from putting a tandem in certain slots. This stems from the days where there was a limit on 42 poles in the panel.
Click to expand...
Would make sense if it were attached to a tandem breaker. Every one I seen like OP pictured is on a two pole breaker just like he has.
Keep in mind these are always on QO breakers that I am certain came from sometime before the 1970's when the tandems that were out there had no rejection features.

I bet if I look through what older breakers I do have I can find a couple like that. (not sure why I'm keeping them)
 
The QO circuit limiting feature is a 'hook' not this tab.

I only saw this tab on larger ampacity breakers. I have never seen the official description of why they existed.
My technical literature from 1960 does not mention this construction. My guess is they were to provide stability when the larger conductors were used with 2 pole breakers in the older metal interiors. A similar construction existed on 2 pole QF fusible devices.
 
jim dungar said:
The QO circuit limiting feature is a 'hook' not this tab.

I only saw this tab on larger ampacity breakers. I have never seen the official description of why they existed.
My technical literature from 1960 does not mention this construction. My guess is they were to provide stability when the larger conductors were used with 2 pole breakers in the older metal interiors. A similar construction existed on 2 pole QF fusible devices.
Click to expand...
Over 60 (maybe 70) amps and those breakers back then spanned across both sides the panel and took up four single pole spaces. That alone provided a fair amount of securing/stability of the unit. Then if it were a main breaker it still had an additional hold down clamp.
 
Over 60 (maybe 70) amps and those breakers back then spanned across both sides the panel and took up four single pole spaces.
[/QUOTE]

No.
It was only the 80, 90, and 100A that spanned across the panel because they were Q1 construction until the late 70's.

The stab does not show up in any of my literature, so it served no specific purpose like circuit limiting or breaker securing.
I only saw it on 2 pole devices, which is why I assumed it was for stability.
 
jim dungar said:
Over 60 (maybe 70) amps and those breakers back then spanned across both sides the panel and took up four single pole spaces.
Click to expand...

No.

It was only the 80, 90, and 100A that spanned across the panel because they were Q1 construction until the late 70's.

The stab does not show up in any of my literature, so it served no specific purpose like circuit limiting or breaker securing.
I only saw it on 2 pole devices, which is why I assumed it was for stability.
[/QUOTE]
did you look at 480's link?

Doesn't make sense to have them today, but back then maybe it did if it were like I said a similar thing to having type S fuseholders.

This would have been at a time when there were still a lot of fuse panels around, and probably lots of temptation for non qualified to put in a larger breaker for one that gives them frequent tripping. Granted if determined enough they probably find a way to get it done anyway, but this was something to make it a little harder maybe? According to his link there was something like this on even single pole 30 amp breakers - though I have never seen it.
 
kwired said:
Doesn't make sense to have them today, but back then maybe it did if it were like I said a similar thing to having type S fuseholders.
Click to expand...

You are probably correct.

I have the speciation catalog in front of me right now. So this is probably the best answer we will have,
How my loadcenter sheets from 1960, refer to a UL Class NI construction feature that limits installation of breaker to 15 and 20A in any position. The mouning rail need a hole punched into it to accept a breaker 30A and larger (Square D even had a tool available for punching this hole). According to the writeup this 30A restriction was a requirement of the NEC to prevent unauthorized people from putting higher breaker in place of lower rated ones.
The breaker dimension drawings, dated 1967, does not show this stab on any QO breaker, so the NEC must have been changed by that time.

Oh, I also noticed the 70A breaker would have been a Q1 construction also.
 
I wonder if it was part of a locking device during that period that breakers were designed not to be removed? Cutler Hammer had tamperproof screws that did not allow you to remove the bolt-in breakers. Wish I had a picture of it, but that building is long gone now, panels and all. I had heard about them from an instructor at the tech school I went to, and actually seen one a couple of years later. Supposedly they found out it was a bad idea, and discontinued it.
 
servlet.ImageServer
 
Just guessing...
Perhaps a rejection feature that would only allow the higher amperage breakers to be installed near the top of the panel?

My daughter’s house has a 1960 vintage QO panel that I’ll try to go have a look at once I’m out of quarantine!
 
retirede said:
Just guessing...
Perhaps a rejection feature that would only allow the higher amperage breakers to be installed near the top of the panel?

My daughter’s house has a 1960 vintage QO panel that I’ll try to go have a look at once I’m out of quarantine!
Click to expand...
According to my 1960 spec sheet, there were no 'factory' supplied spaces for the 30A and larger breakers. The hole would be punched in the field by a not 'unqualified person'.
My 1968 spec sheet no longer refers to this NI feature.
 
Status
Not open for further replies.
Top