Installing new 220v circuit breaker

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Old 10-26-09, 04:36 PM
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Installing new 220v circuit breaker

This is a very basic (naive?) question about 220v and 110v power inside my breaker panel.

I need to install a new 220v circuit in my breaker panel, and there are no remaining slots (I believed I needed a dual slot for the wider 220v breaker). An electrician looked at it and told me I can remove the existing, old style WIDE 220v breaker that is there for existing A/C, and replace it with two NARROW style 220v breakers--that the narrow style will fit into a single slot, so two of the narrow ones will fit into the same two slots now occupied by the one WIDE breaker; and I will end up with one of the new NARROW 220v breakers available for the new circuit I need.

I understand the red wire, black wire business for wiring 220v (downstream of the panel). What I don't understand is how does the circuit become 220v simply by installing a "220v" breaker? I assume the power coming into the house is 110v, but maybe this is the source of my confusion. I have a 220v dryer and 220v A/C, so obviously there is 220v power there. Does the power to the house come in as 220v and it is then "split" at the breaker panel? Or is there separate 220v service and 110v service, with the 220v service attached to those breakers that handle the 220v? I have not examined the 220v breakers in detail, but I have installed extra 110v breakers in this same panel and my recollection is that all the breakers are attached to the same power source (the breakers snap onto a live copper vertical bar in the panel, which is the incoming power side of all the breakers). If this is the case, how do some of the breakers become 110v and some are 220v? It the source bar is 220v, and the 110v comes from attaching only 1 black and one white (neutral) to the breakers intended for 110v circuits, then that may explain it.
 
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Old 10-26-09, 04:47 PM
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There are 2 hots legs in your panel. Each leg to ground is 120 volts. Between each leg is 240 volts. Typically every other breaker is on the alternate leg from the one above and below it. Imagine all the fingers on your left hand as A and all the fingers on your right hand as B. Now interlace your fingers. Between A and B is 240 volts, between either A or B would be 120 volts. A 2 pole breaker would hit both an A and a B finger on the buss.
 
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Old 10-27-09, 11:14 AM
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Makes sense. It sounds like all I need to do is pull the existing WIDE 220v breaker and pop in 2 NARROW ones and I'll have the new 220v circuit available to connect to. Thanks.
 
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