Can a 240V circuit be split to make two 120V circuits when 240V is no longer needed?

Question

I have a 240V circuit that is no longer needed. Can I split it into two 120V circuits?

Answer 1

Short answer - you can easily convert to a single 120V circuit but you can't convert to two circuits, you have two wires and you need three or four.

Your 240V branch circuit is supplied by two wires originating at a two pole breaker in the panel. You could remove the two pole breaker, install a single pole breaker, land one wire on the breaker and the other on the neutral bar, and you have a 120V circuit.

To get two 120V circuits, you have two options:

• two separate circuits wired with four wires
• a single multiwire branch circuit with three wires - two hots and a shared neutral

If you're wired with conduit and have the space, it's usually pretty easy to add one or two wires from the breaker to the outlets. If you're wired with cable - either nonmetallic / romex or armored MC / AC / BX, it's more of a project. But it's not a simple conversion.

Answer 2

First, this will not be possible unless the 240V line has a ground/safety earthing wire. However, ground wires can be retrofit. It will also only work in North America, Japan and a few nations in South America.

Case 1: a 120/240V circuit with neutral wire

If there is a neutral wire present with the two hots, you can create a multi-wire branch circuit aka shared neutral. You can extend off of it with two circuits, one grabs one hot and neutral, the other grabs the other hot and neutral. You will need to reduce the breaker size, and you must use a 2-pole breaker where both sides throw together, not a duplex/twin/double-stuff. The breaker must be a 2-pole 15A if any wire in it (old or new) is 14 AWG in size (or #12 aluminum). Otherwise a 20A breaker is correct.

Case 2: A 240V only circuit, with black and white wire

In this case, you can make one circuit out of this by moving the white wire from the circuit breaker to the neutral bar. You may need to resize the breaker, the same rules as above. You are free to replace the 240V 2-pole breaker with two 1-poles, or a 1-pole and a blank cover, or a 2-pole breaker will also be fine (you'd only use half of it).

Case 3: You are in the conduit wiring method with individual wires

In this case, the individual wires are both colored (not white or gray) and all go through conduit together and follow a specific route. You can fish in an additional white wire on the same exact route, and then follow case #1.

Case 4: Transformer and subpanel

You have to really want this one, because it'll cost. You feed the 240V output of the existing circuit into a transformer. Have that feed a subpanel and tap your new circuits off the subpanel. The details are beyond the scope of this answer.

Otherwise, no, you cannot do it.