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Hey Folks,

Concerning installing 240v power I've noticed sometimes its required to have a 3 wire/wgrnd and other times it seems only a 2 wire/wgrnd is required. Can someone explain when and why there are sometimes different requirements? Is it an Amp related reason?

It helps when I can understand the concept/reasoning.

Thanks
 

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Hey Folks,

Concerning installing 240v power I've noticed sometimes its required to have a 3 wire/wgrnd and other times it seems only a 2 wire/wgrnd is required. Can someone explain when and why there are sometimes different requirements? Is it an Amp related reason?

It helps when I can understand the concept/reasoning.

Thanks
It is a voltage question. 240 V equipment needs two wires and a ground. But 120/240 V equipment needs three wires and ground. Your electric clothes dryer, for instance is NOT a 240 V appliance. It is 120/240 V. The dual voltage rating means that the appliance itself has some internal equipment that use 120 V, and other parts that use 240 V. A neutral is needed in this case to supply the 120 V loads.

Wire size, on the other hand, is determined by amps. An amp is an amp, no matter what voltage.
 

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Registered
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1,758 Posts
Hey Folks,

Concerning installing 240v power I've noticed sometimes its required to have a 3 wire/wgrnd and other times it seems only a 2 wire/wgrnd is required. Can someone explain when and why there are sometimes different requirements? Is it an Amp related reason?

It helps when I can understand the concept/reasoning.

Thanks
Two hots and a neutral are needed for a 120/240 circuit, like a dryer. Part of the dryer runs on 120, while the heating element requires 240. The neutral allows for a return path for the 120V portion of the circuit. A 'straight' 240V circuit requires two hots and a ground. The two hots complete the 240V circuit, no neutral is required. The ground is required for both, of course.
 
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