Dimming fluorescents...

I've known for some time now that the Europeans use 230 volts and that we Americans use 120 volts for most household items and 240 volts for large appliances. Even though I've never really given it much thought, I've always imagined that the US system is somewhat less efficient than the European system because of the lower voltage and higher amperages that our electrical devices have use to compensate for the lower voltage. But I was talking to an electrician the other day and he told me that this is not really the case between the breaker box and the transformer. According to him, if all the 120 volt loads that are connected to one hot leg exactly matched the loads that are connected to the other, it would be as if half the loads were connected in series with the other half. At the same time, you would find that the neutral is not carrying any current at all. In the real world, some of the current does have to pass through the neutral since the loads being imposed on both legs are not perfectly balanced. But most of the current that's delivered to our homes comes as 240 volts through the hot wires because of this effect. This would also explain why a double receptacle circuit with a shared neutral wire doesn't have to use a neutral wire that can accommodate the amperages of both 120 volt hot wires. Could this also mean that a double receptacle circuit connected to two individual breakers on the same leg could overheat the neutral wire? Robert

I am doing some work on a small horse barn, and they currently have one 220V Mercury vapor light installed in the roof joists. I am trying to find out how much it is costing to operate this light and compare it to flouresent or smaller 110V sodium vapor lights. Does anyone know where I can find a cost comparsion based on type, size and length of usage? The light is approx. 15 feet off the floor. Thanks.