Square D three phase breaker

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Greg1707

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Location
Alexandria, VA
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Business owner Electrical contractor
Can someone comment on this panel and breaker? It is a three phase Square D panel. The last breakers at the bottom are different from the ones above. They are much wider. Why are they different. I was told by Square D these breakers are obsolete.
 

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kwired

Electron manager
Location
NE Nebraska
I don't know much about the bolt on style as shown in the pictures (not sure how these wide breakers connect to the bus in a bolt on panel). I have seen many plug on style that are same way. 70 - 125 amp were all in a larger frame and took up space on both sides in a plug on panel. (a two pole would use up spaces 1,2,3 and 4 and not just 1 and 3 or 2 and 4).

I don't know when they quit making them probably mid to late 1970's. I think they figured out how to make them more compact. That was also time when they had a lot of panels with aluminum bus and I have seen many of these fail where the breaker plugs on to the bus. The aluminum bus may have been part of the reason as these breakers had about twice the size plug on jaws as the smaller breakers had.

The breakers that are a replacement for them are the ones that are installed in new panels. They just quit making them in the wider frame.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
The bottom breakers are type Q1. As Kwired said, the original the QO breaker was limited in ampacity.

QO breakers are directly interchangeable with the Q1 devices.
There were some "Top Feed" Q1 devices used as main breakers in some loadcenters which do not have direct replacements.
If you go back far enough, you can find that the Q1 family went as low as 15A. Back in the 50's there were Federal Specifications that called for E-Frame, or full width, breakers. Changes to these specs occurred in the 60's allowing for Square D to phase out of the smaller sizes. Eventually, in the 80's, the entire Q1 family was replaced by QO.
 

kwired

Electron manager
Location
NE Nebraska
The bottom breakers are type Q1. As Kwired said, the original the QO breaker was limited in ampacity.

QO breakers are directly interchangeable with the Q1 devices.
There were some "Top Feed" Q1 devices used as main breakers in some loadcenters which do not have direct replacements.
If you go back far enough, you can find that the Q1 family went as low as 15A. Back in the 50's there were Federal Specifications that called for E-Frame, or full width, breakers. Changes to these specs occurred in the 60's allowing for Square D to phase out of the smaller sizes. Eventually, in the 80's, the entire Q1 family was replaced by QO.

Do you know how the breakers in the OP photos attach to the bus? This is a bolt on panel. I have never seen the Q1 breakers in a bolt on panel before.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Do you know how the breakers in the OP photos attach to the bus? This is a bolt on panel. I have never seen the Q1 breakers in a bolt on panel before.
There are a series of "Z" connectors that run from the staggered panel bus to the 'line' end of the breaker where the bolt-on screws are located.

The mounting assembly part number for NQOB panels was SK-5666 (list price was $6.30 back in 1970)
 

Greg1707

Senior Member
Location
Alexandria, VA
Occupation
Business owner Electrical contractor
Reply from Square D Technical

Reply from Square D Technical

Here is the response I got from Square D after sending photos:

"Thank you for contacting Schneider Electric !

This breaker is obsolete. It can be replaced with a QOB3100 breaker and an SK5668 mounting kit ."
 
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