NQO breakers

[nizak]

I am looking at converting an existing fast food establishment into retail space. I opened the 2 panels (Sq D NQO 225A 120/208 3 phase) and noticed on what appears to be the original install QO plug in style breakers were used. Out of the total 84 spaces only 6 breakers are of the "bolt on type". Does anyone know if using the conventional plug in style QO's is a violation in this particular panel? I won't be back to the site for a few days so I'm unable to see what's listed for breakers on the cabinet interior. Thanks.

 

[LEO2854]

I am looking at converting an existing fast food establishment into retail space. I opened the 2 panels (Sq D NQO 225A 120/208 3 phase) and noticed on what appears to be the original install QO plug in style breakers were used. Out of the total 84 spaces only 6 breakers are of the "bolt on type". Does anyone know if using the conventional plug in style QO's is a violation in this particular panel? I won't be back to the site for a few days so I'm unable to see what's listed for breakers on the cabinet interior. Thanks.

The last time I worked on one of those, it seems those breakers are made for those panels.


This is from the squire D web site;

What is the difference between NQO and NQOD panelboards.

NQO is an obsolete panelboard that accepted plug-on breakers only and the NQOD is a current panelboard that accepts plug-on and bolt-on breakers.

 

[augie47]

One of our esteemed members, Jim Dungar, addressed way back when. If I may I will quote him:
In the 70's and 80's it was very common to see specifications that said "Panelboards shall be Type NQO - or approved equal - as made by Square D, General Electric, Westinghouse, and Cutler-Hammer".

In reality NQO was a type of Square D panelboard, rated 240V max, that used QO plug-on breakers. Its sister panel was the NQOB, which used QOB bolt-on breakers. These panels were replaced around 1990 by the NQOD one, which accepted both style breaker. The current generation of panels is the NQ.

For the trivia buffs, Square D has used the prefix letter N to indicate a 'lighting and branch circuit' style panelboard since the 1940's, the letter Q has been used to mean 240V max equipment since the 50's, and the letter O probably started out as a number 0, since there are breakers numbered Q1, Q2, and Q4 as well as QO.

 

[GoldDigger]

So my question for the OP is how are those six bolt-on breakers fitting into the NQO panelboard?
Are they in feeder positions or otherwise specially located?
Or is it actually an NQOD panelboard?

 

[jim dungar]

So my question for the OP is how are those six bolt-on breakers fitting into the NQO panelboard?
Are they in feeder positions or otherwise specially located?
Or is it actually an NQOD panelboard?

It was possible that somebody field modified the NQO panel to accept bolt-on breakers by using an appropriate branch breaker assembly. This was not a common practice, although I believe it was sometimes done when a 'retained' breaker was required, like for a backfed main.

The NQOD, and now the NQ, did away with the either/or branch assembly and each space can now accept both style breakers.

 

[StarCat]

Field Report

Field Report

It was possible that somebody field modified the NQO panel to accept bolt-on breakers by using an appropriate branch breaker assembly. This was not a common practice, although I believe it was sometimes done when a 'retained' breaker was required, like for a backfed main.

The NQOD, and now the NQ, did away with the either/or branch assembly and each space can now accept both style breakers.

I have 2 of those panels on property and they both sport both kinds of breakers inside as I found them.
All appears normal.

 

[rt66electric]

3p or 2 pole same panel

3p or 2 pole same panel

I know of a house built in the 50's looks like a normal SquareD QO panel,,, BUT.....

It had a 3 phase riser to the meter then to a 3p M.L.O. board..

the top 3 slots were 3 phase, then the rest were 2-pole.????

(someone else incorrectly added a 3phase subpanel, A-phase A-phase and B phase????)

The bus-tabs were interchangeable. a person could move the bus-tabs to whichever phase was needed.

 

[jim dungar]

the top 3 slots were 3 phase, then the rest were 2-pole.????

This was a typical construction for a 240/120V 3-phase 4-wire panel. A limited number of 3-phase spaces meant there was little chance of plugging on to the high leg by mistake.

There might have been some type of commercial enterprise associated with the 'house' that required 3-phase power.