Sunday, January 27, 2008

240 volt circuits

Here is where 220-240 volts starts:

The buss bars in the breaker box are set up to where every other position is a different phase. This means that there are two separate 120 volt power sources coming from the 240 volt breaker.

The small breakers with only one hot lead are called single pole breakers. The ones with two hot leads are double pole breakers.

In a 240 volt circuit is referred to as ungrounded. What that means is, there is no neutral conductor involved. Here is a simple 240 volt circuit:

This diagram shows only the circuit and switches for a 240 volt motor. Only 2 wires of 120 volts are needed. The power comes in through both wires and is neutralized within the motor. Power does not have to travel back through a neutral conductor.

Shown is a perpendicular 240 volt outlet. In reality the motor would be plugged into the outlet with a matching plug. There are several kinds of 220-240 volt outlets and plugs. Here are some.

The 20 amp can be found on some room air conditioners. The 30 amp can be found on clothes dryers. The 40 can be found on some electric ranges.

In some instances the grounding conductor is used as a neutral. I am not sure exactly how this works, but it is allowed. Here is a demonstration:

This is a 220-240 volt clothes dryer. The motor and heat element are 220 volts. The motor control circuit (including the timer) is 120 volts. In some cases there is a 4 wire plug and outlet that utilizes a neutral wire.

This diagram is not correct as shown, but only for demonstration purposes. In reality, there would be switches and the motor control circuit operating the unit.

Each chapter in this series is to give you general information. It is my hope that it will encourage you to learn more about electricity as it can be a most fascinating thing.

The last chapter is a review of the series. I hope you have enjoyed. :)

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