Originally Posted By: Gino Conner
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The service conductors that you are referring to can be aluminum or copper. In my area, most are aluminum. Some areas may require copper. In an area where either is acceptable cost will probably be the deciding factor as copper is more expensive than aluminum.
You are on the right track with your thinking. In dwelling units your 240/120 appliances are usually kitchen stove and clothes dryer. Both usually use the 240v that is available between the two power phases to power the current demanding heating elements, and the lower 120v to power the control circuitry, lamps, clocks, etc.
There are other appliances that can require 240/120. For example, I have a GE Advantium Microwave oven in my kitchen that requires a 240/120v 30a circuit because in addition to conventional microwave cooking it also has upper and lower heating lamps (Quartz Iodine I believe) to cook significantly faster and allows for browning.
There are also appliances that require 240v only. Two commonly found examples are central air conditioning system condenser units and heat pumps.
Does this help to answer your questions?