220 double pole breakers

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  #1  
Old 12-26-01, 06:41 AM
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220 double pole breakers

I would like to know if you have a double pole circuit breaker 2 x 120 and you have 30 amp breakers in each pole is that double the amps for a 220 line? In other words you have 60 amps generated at 220 volts? Or is it 30 amps at 220? Thanks
 
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  #2  
Old 12-26-01, 08:34 AM
Wgoodrich
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The 60 amp rating of a 240 volt breaker is 60 amps. Try to follow the following circle.

120 amp 120 volts = 60 amp 240 volt or 30 amps 480 volts.

Example.

14400 volt amps [or watts approximate] if run using a 120 volt power source your amp load would be calculated by dividing 14400 Va / 120 V = 120 A

14400 volt amps if run using 240 volts power source your amp load would be calculated by dividing 14400 Va / 240 V = 60 amps

Yet 14400 volt amps if run using 480 volts power source your amp load would be calculated by dividing 14400 Va / 480 V = 30 amps.

The volt amps [approximate watts] are relative to any of the voltages.

It takes only one phase to use 120 volt [single breaker] 120 @ 60 amps would carry only half as much work as the same double pole breaker. [2 -120 volt breakers made as one tapping to two phases]

When it says 60 amp 240 volt it means a total of 60 amp @ 240 volts.

When it says 60 amp 120 volt it means a total of 60 amp @ 120 volt.

60 amp multiplied by the voltage 240 volts = 14400 Volt amp capacity.

60 amp multiplied by the voltage 120 volts = 7200 Volt amp capacity.

Hope that helped

Wg
 
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Old 12-26-01, 11:23 AM
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If you had a two pole, 30 ampere circuit beaker, no matter what voltage, the trip device will allow 30 amperes max in each of the two poles before tripping. If you could draw 10 amperes in one pole and 35 in the other, both poles will trip simultaneously because one pole is overloaded. Think of it as two single pole 30 ampere circiut breakers with their handles tied together. So you could have a multiwire circuit drawing up to 60 amperes if you drew equal amounts of current from each pole (phase).
 
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Old 12-28-01, 03:43 AM
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30amps is 30amps regardless of the voltage.

you have 30 amps at 220v.

It gets more complex when you discuss Power. You have 2 times the power i.e. "Watts" Hopefully this feed is to a 220v "appliance" and not some kinda split circuit. Regardless the breaker will trip if you exceed 30amps in either leg.

hope this helps
 
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