Does a 220v circuit have double the amperage capacity?

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  #1  
Old 05-18-12, 01:52 AM
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Does a 220v circuit have double the amperage capacity?

Hey all,
Im not much of an electrician, so i had a question regarding 220v circuits.

If the circuit is hooked up to a 20a breaker does that mean that EACH hot wire has the capacity for 20a giving the outlet a combined total of 40a? Ive always been a bit confused about that.
 
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Old 05-18-12, 03:18 AM
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Nope, each leg works independently of each other at 120 volts. One leg has an overload the entire breaker turns off, as witnessed by the bar across the handles.
Read up on Ohm's law....Higher voltage, lower amperage use. Conversely lower voltage, higher amperage. For instance a table saw that is pulling 13 amps at 120 volts will pull 6.5 amps if the motor is wired (or can be wired) for 240 volts. Wattage is the same, so there is no savings regarding metering the two.
 
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Old 05-18-12, 08:15 PM
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Not to hijack this thread, but kind of the same subject. What if 120 volts were run to a subpanel, than a jumper was used to make the other side of the panel hot? Would that in theory, give you 240 volts? Or, would that be 240 volts with the same amperage as the 120 volt feeder?
 
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Old 05-18-12, 09:23 PM
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No, it would just be a 120v subpanel and there would only be 120 volts present. That is in fact done in special cases such as a 120v only panel in an RV. I think you are thinking that 240 volts is derived from two 120 volt feeds but it isn't. Actually your house is supplied with 240v and the 120 volts is derived from one leg of that 240 volts and the grounded center tap of the secondary of the transformer suppling your house.
 
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