120/240 volt--general question

diyjunkie

I've seen references in books and on this forum to "120/240 volts", but I'm confused as to the meaning. Is there a circumstance where you would put in a "120/240 volt" circuit, or are circuits normally either 120 or 240 volts? I have no particular project in mind--just curious and haven't been able to find an answer. Thanks.

Julius793

Each leg is 120 and will add to 240 then again every thing needs to be taken in context because people don't write what they mean.

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rjniles

Most general purpose receptacles and lighting circuits are 120 volt (either 15 or 20 amps).

Some appliances like a water heater are 240 volt.

Some appliances like a kitchen range or a clothes dryer are 120/240 volt. The use the 240 for the heating functions and use 120 for things like timers and clocks.

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diyjunkie

Thanks for the replies. So a recepticle will be wired for either 120 or 240. If an appliance needs both, it would have two plugs. Right?

Speedy Petey

No, it would have a 4-wire plug.

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Daltex

An appliance uses 4 wires like posted. One is a ground- this is not always present thus a 3 wire plug is sometimes seen and the neutral attaches to the case via a strap. One is the neutral. The other two prongs are both 120 volts.

To get both 240 and 120 V off the same plug, the appliance will only attach a connecting wire to one of the 120V lines and use the common neutral. The heating element (or motor or whatever needs the full 240V) would attach to both of the 120's. Thus one plug carries the supply for both the 240 needs along with the 120.

diyjunkie

Thanks, all. This is scary! I actually think I understand this now!