Why do they make this breaker?

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chevyx92

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VA BCH, VA
These pics are from a Square D I-Line Panelboard 480V. The breakers in the panel as you can see occupy 3 spaces but they are actually 2 pole breakers. Look close you will see there is no lug on "B" phase on these breakers. And no its not broken. These are factory made. Its a waste of space!! Has anyone else seen these and why would they make a 2 pole breaker that looks like and takes the space of a 3 pole? :confused:
 
Seems like a bad design to have all dp breakers in a 3 phase panel. I assume it is 3 phase, No? All loads would be on 2 phases so you would need to calculate the load based on that.

I assume they are made that way simply because they need the room for the components of the breakers. I would guess there are no sp I-line breakers available.
 
1 pole are available.
2 pole are available.
For the two pole, phase options are AB, AC, BC.

Reference is SQD digest 175, p9-24

I've never needed to use this option. I can't think of a reason why one would. However, SQD likely wouldn't show the option available unless there was a market - I just don't know what it would be.

cf
 
Seems like these are 3 pole breakers with the center terminal remove, Ive seen these around but can't remember where or why but if you notice the 5th breaker down is a "true" 2pole breaker
 
You can order the I-Line breakers by phase so you can balance the load.
On stab or bolt on panels you could just skip the stab where the I-Line design won't allow this.
 
shepelec said:
You can order the I-Line breakers by phase so you can balance the load.
On stab or bolt on panels you could just skip the stab where the I-Line design won't allow this.
Click to expand...
shep -
I'm not disagreeing with you. But SQD even makes these for QO panels. They even make a 3 pole I-Line with CBA

:confused:

cf
 
I could see the QO breaker for 120/240 applications on a high leg delta. Though most of us would just count the phases and use a 2 pole.

I do not know about the CBA on the I line, that would seem to be a specialty item maybe for connecting to a buss system in a control cabinet.:confused:
 
Dennis Alwon said:
okay good info but no one has suggest why the breaker takes up 3 spaces. Does the SP also take up 3 spaces?
Click to expand...

No the 1pole is made to just take up 1 space the 2 pole 2 spaces (see breaker #5 from top). Why anyone would use this type of install is beyond me seems like a waste of breaker space.
 
Standard 2-pole breakers take only 2 spaces, but these breakers are made special for 480V Corner-Grounded (grounded B-phase) systems. Even though they are only 2-pole they are built using a 3-pole frame.
You can find more information in Square D's Supplemental Digest.
 
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jim dungar said:
Standard 2-pole breakers take only 2 spaces, but these breakers are made special for 480V Corner-Grounded (grounded B-phase) systems. Even though they are only 2-pole they are built using a 3-pole frame.
You can find more information in Square D's Supplemental Digest.
Click to expand...
Jim do you work for Sq. D? You seem to have a wealth of knowledge about them.
 
Dennis Alwon said:
Jim do you work for Sq. D? You seem to have a wealth of knowledge about them.
Click to expand...
Among other things, I was a Square D sales engineer for 11 years (basically during the 80's). For the past 6 years I have not been directly involved with Square D products.
 
Its a frame size - all of the breakers in that frame size will be the same. Go to the next frame size - bigger... They are sized by Amperage and AIC - not the number of poles - while you might be hard pressed to find a single pole CB the over 100A I don't think I've seem them*, 2-3 poles are all 3 pole cases of that frame no matter if there are 2 or 3 poles of the breaker actually in it.

*See page 12
 
Although I don't have the answer to the OP question, I would GUESS that they do this to give you the maximum number of options in your switchgear. I work in a large building that had the original 1930's gear (all exposed bare copper buss) replaced with this same gear. The building is 208v, but the switchgear is 600v rated. They used all 3-pole breakers, even though most of the loads are single phase panels. They just used 2 poles on most of the breakers. As somebody pointed-out, if you wanted to have a 2-pole load on A & C, you would need one of these. (or if you were trying to avoid the high leg on a delta system) Who knows? But as you can see, they can be 2-pole (2 space) as well. One thing I KNOW. These breakers are VERY expensive!
 
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