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How do you get 120V from a single circuit breaker box that has a 240V line coming into the box that has one black one white and one bare line?


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Wiki User
2015-07-15 20:55:21
2015-07-15 20:55:21
The s given below are ONLY for USA, Canada and countries using similar 120/240 Volt, 60 Hz mains power supply systems.If the box has 3 wires at 220V you can't get 110V. The reason is you have the two hots and the ground, but not the neutral. If you pull a neutral through the conduit or re-run the *-2 wire with *-3 you can get 110V at this panel.


However, if you no longer want 220V at this fixture you can derate it to 110V. The key here is the current capacity of the old wire. You cannot exceede the current capacity of the wire as that is a fire hazard. Also the fixture must be on a dedicated circuit. You cannot mix 110 and 220, you have to derate the whole circuit. To derate:

  • Get a 110V fixture of equal or lesser current to the old one that you want to use.
  • Get a 110V appropriately sized for your fixture.
  • Remove the 220V breaker and replace it with the 110V breaker. The white wire that went to the breaker now goes to your neutral bus.
  • Replace the 220V fixture with the 120V.

Always, if you are not 100% sure of what you are doing, buy a book. It will answer your questions and serve as a handy reference during the job. Do it right or hire a professional. Negligence is fatal with electricity.IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB



If you do this work yourself, always turn off the power

at the breaker box/fuse panel BEFORE you attempt to do any work AND

always use an electrician's test meter having metal-tipped probes

(not a simple proximity voltage indicator)

to insure the circuit is, in fact, de-energized.


Related Questions

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Depending on how the two wires are connected in the circuit ,one scenario is the breaker to that circuit will trip.

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If you need a 220v circuit at only 15 or 20 amps: Get a new breaker to replace your 110v single pole breaker with a 220v double pole breaker. (You cannot exceed the original breaker's amperage rating unless you also replace the wire with a larger size). Shut off the panel's main breaker (the wires coming into the main breaker will remain hot, so don't touch them.) Remove the old 110v circuit's neutral (white) from the neutral bus bar in your distribution panel. Remove the old 110v circuit's hot (black) from the old 110v breaker. Remove the old 110v breaker. Install the new 220v breaker in place of the old breaker. (This may require you to rearrange some breakers if the old breaker was in between others) Reconnect the black wire to one terminal of the 220v breaker, and reconnect the white wire to the other terminal. Turn on the main breaker, and your new 220v breaker. Before you do this, be sure where the actual circuit goes. Changing 110v to 220v if the circuit is feeding regular 110v receptacles will cause damage to devices plugged into them. Be sure you remove all 110v devices (receptacles) from the circuit before converting it. If you need a 220v circuit for a dryer or other large appliance, your existing wiring will not be sufficient to do the above. You will need to install a new breaker and wiring. For this task, you should consult a professional electrician.

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Simple. The branch circuit you're feeding with the breaker should have a black, (hot), a white (neutral), and a bare ground wire. The bare ground gets screwed under the ground bar with the other grounds. The black wire goes under the appropriate screw on the breaker. Also the neutral goes to the breaker under the screw with a white dot by it. Then the curled up white wire attached to the breaker gets screwed into the neutral bar where all the other white wires are.

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