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Circuit Breakers Voltage Ratings

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jcrollman

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I have a question regarding circuit breaker voltage ratings. I am looking at a breaker (the allen bradley 1489) which can be purchased in the 1/2 to 25A range for a 480Y/277VAC distribution system, or 1/2 to 40A range for a 240VAC system.

My question is, can these breakers be used in other systems?

What if I tried to use the afformentioned breaker in a 240Y/120V system? Would it trip in a different current range? Why or why not?

Thanks,

Jeff
 
All circuit breakers trip at their rated current. They pay attention to current, not voltage.

Circuit breakers have a voltage rating because the amount of current the breaker can safely interrupt is determined by the voltage. As you can imagine, a higher voltage creates a larger and longer arc which is more difficult to interrupt. In the worst-case the arc would not extinguish and the fault current would keep flowing even with the breaker open, at least until the contacts were completely burned away. Some larger breakers have a magnetic coil in series with the circuit that generates a magnetic field across the contact gap to help blow out the arc. Thus the higher the fault current, the larger the magnetic field.
 
So from my understanding then, it would be ok to use the aforementioned breaker on a 240Y/120V system, but not on a 600Y/347V system due to the possibility of interrupt failure.

If I were to use the breaker on a 240Y/120V system, would that cause any listing (say UL) violation because it is rated at a specific voltage? Or is that rating simply a max, and any voltage under the rated voltage is appropriate?
 
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You can always use a breaker at less than the rated voltage (which is a maximum rating). But you should not use a breaker at above it's rated voltage.
 
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