120 and 240 VAC question?

As quick and easily as I can explain this:

When you think of the word, "circuit" think of circle. A circuit must form a complete "path" or circle for current to flow. 120 Volts needs a neutral so that a complete path can be formed. 120 is the measurement of what's called "difference of potential."

240 Volts has two hots or ungrounded conductors. These two provide a path as each one comes from a different "phase" on the power supply.

A water heater works kind of like a light bulb. A light bulb connects the hot and neutral together inside the bulb which is why it glows. It's called a controlled dead circuit or resistive lighting. The water heater elements are the same. Phase A connects to phase B within in the element, thereby producing the heat.

I know this is no where near an in depth answer, but I hope it gives at least the idea. There is much more to be said, but not to be typed.

E-mail me from my site and I'll be glad to explain further if necessary.

Try this answer for simplicity. A 120 volt circuit has 120 volts between the hot wire and earth ground, usually a green wire.

A 240 volt circuit is two 120 volt circuits, but they are 180 degrees out of phase with each other. Therefore, because the two circuits are out of phase with each other there will be 240 volts between them. The current travels between the two 120 volt circuits, and therefore no ground is necessary.

This is why only two power wires come from the power pole to your house. The earth ground is only necessary when using an 120 volt circuit alone.

Thus: in 240 volts, the current travels between the two phases, and in a 120 volt circuit the current travels between the hot wire and earth ground.

I'm not a master electrician, but I've been working with and teaching basic electricity for a long time and it's always been my understanding that a 220 volt line is just like having two 120 volt lines side by side. If you have two pieces of #10 romex wire, with a black, a white and a ground in each and you connect the two whites together, the two grounds together and attach the two blacks one each to the hot sides of the switch with the whites connected to the neutral bar, and the grounds to the ground bar you should have 220 across the two black lines and 120 to each of the two black/white combinations. In all of these switches I've installed, you have to bring a lead off the 120 side as the timer is run by 120 instead of 220.

I couldn't have explained it any better, Rick. Good job!