What if I have a three prong plug 240 volts and want to convert to 120 volts?

Answer 1

For USA, Canada and countries running a 60 Hz supply service.

If you're asking this question you shouldn't be installing an electrical service.

If someone were to give you an answer here, you might attempt to do something you shouldn't be doing, and that may cost someone a shock, a home fire, or their life.

If you don't want to have a new 120 volt branch circuit correctly installed in that area, to be able to use the appliance there, you should just plug it into an existing 120 volt outlet somewhere else.

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You want to power an appliance which has a 3 prong 120 volt plug: One hot, one neutral, one ground.

But, where you want to use the appliance, you have a 3 prong 240 volt outlet: Two hots and one neutral or one ground.

So you either have the ground and not the neutral or the neutral and not the ground.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

Answer 2

If you are referring to US household power, the three prong 240VAC appliance plug is simply two opposite phase 120VAC lines sharing a common neutral. The hot lines are black and red (pick either one) and the common neutral is white. This has no ground/earth wire.

However if this is going to be a permanent connection, to meet code I believe you need to insert a fuse or breaker in the "new" 120VAC circuit as the existing 240VAC dual phase breaker might not trip reliably.

If this is not US household power, a transformer is probably necessary as it would probably be single phase 240VAC with hot, neutral, and ground/earth wires.