I currently have a well house that has a 240V source on 12-2 wire powering a submersible well pump. I would like to wire in a 120V light. Can this be done using the 12-2 wire already in place or do I need to remove the 12-2 wire and install 12-3 wire? (It is approximately 60ft from the main house breaker to the well house and the wire runs underground.)

I understand that if I use 12-3 wire then, the neutral (white wire) is connected to the neutral strip of the panel, the two hots (black and red wire) come out from the double circuit breaker and the ground wire goes to the ground strip of the panel. At the well house, one hot and the neutral make the 120V for the light and the two hots make the 240V for the pump with no neutral. All grounds are connected together.

Hopefully, there is a way to wire in a 120V light with the 12-2 wire I already have in place.

Thanks.

This statement is exactly correct:


I understand that if I use 12-3 wire then, the neutral (white wire) is connected to the neutral strip of the panel, the two hots (black and red wire) come out from the double circuit breaker and the ground wire goes to the ground strip of the panel. At the well house, one hot and the neutral make the 120V for the light and the two hots make the 240V for the pump with no neutral. All grounds are connected together.

This statement has no hope, and will not work:


Hopefully, there is a way to wire in a 120V light with the 12-2 wire I already have in place.

The only way you can use the two wire 240 volt circuit is to use a 240 volt to 120 volt transformer at the well house end of the circuit.

Thanks for the help.

In using the step-down transformer, your saying it can be wired using the 12-2 wire I already have in place? Wouldn't this be a better option than running a brand new 12-3 wire?

It maybe, depending on the cost of the xfer, and the cost of the 12-3 plus labor.

Use a 500 watt (.5KVA) dry type xfer, with 240 volt primary and 120 volt secondary. This will provide enough power for a 100 watt lamp, and leave 400 watts for a portable drill, etc. If more power is needed, use a 1KVA xfer.

The primary only will need the 2 wire 240 volt feed, plus the ground, don't ever forget the ground.

I have another question regarding wiring.

If I swap out the 12-2 wire with 12-3, there really isn't any way for one to get the 12-3 wire back into the fuse panel without tearing the wall out. In the crawl space under the house, there is a junction box where the 12-2 240V wire changes from NM-B to UF-B to go underground. Very near to this junction box is a light with 120V wire running to it.

My question: Is it OK to start running the 12-3 wire from this junction box with the two hots back to the fuse panel still on the 12-2 NM-B wire and using the neutral wire from the nearby light to connect the neutral wire of the 12-3 wire?

Thanks again for the help.

Cheapest and easiest thing might be to pick up a European 220 volt fixture and bulb. Take tkrussel's word on whether that would meet code. I doubt he go along with picking up that other neutral. What you could do is extend that circuit to the well.

Absolutely not, your plan with the neutral. No,no. Forget it.

Quite frankly, I did not think of a 240 volt light bulb.

They do make 240 volt light bulbs that are exactly the same as a standard household bulb, and you don't need a special fixture. I don't think of suggesting these in residential because this socket will have 240 volts in it, and if some unsuspecting person installs a 120 volt bulb, they will need a new pair of shorts.

However, you can, with a little searching, find what appears to be a standard medium base socket with left hand threads, and left hand light bulbs.This will prevent the possible hazard of someone screwing a 120 volt bulb in the regular socket with 240 volts and having the bulb explode in their hands.

Labman is always thinking how to save money. I think he still has he first dollar he ever made. Good idea LM!