I have 240V powering our water well (used only for irrigation and not critical to day-to-day living).  The wire is 2 hots plus an unshielded copper ground, and is wired to the pump's pressure switch.

Can I create a 120V leg by wiring a hot to one of the 240V legs and also grounding the 120V at the switch? If so, do I need a neutral & what should it be connected to?

My objective: I've got my Pod parked about 100' away from the house. Only nearby electricity is the water well, and I'd like to stop running out my heavy extension cord for shore power between trips.

Sure will appreciate some advice. I know a bunch of you folks are way ahead of the pack where electricity is concerned, and I'd sure like this to be done right .. and safe.

Thanks in advance ..

I might be inclined to repurpose one of the hot legs as neutral, changing it to a 120v circuit (assuming that the well is no longer in use).  But, its definitely against code.

Ideally, you'd be running 4-wire with the two hot legs, a common (white) and a ground before even considering this as an option.

+1 on this. If you had a 220 like on a household drier of range with 3wire and a ground you coiuld tap 120 off of one side but not with two wire.

Edit:  You could do this with a step down transformer but I have no practical experience with this only theory. 

Generally, in residential wiring for 220 (e.g. stove or electric dryer), you'd see a 4-prong; partially for standardization, partially because some appliances also need 120v (e.g. an oven generally has a 120v light, a stovetop usually has a 120v utility outlet on it).

For industrial applications and sometimes even in home workshops (e.g. arc welders), a pure 220v run will be used.  After all, 3-wire is cheaper than 4.

 

And just to clarify, yes, the well has been operational (30+ yrs) & will remain in service.  Wiring is 2 wire (both hot) + bare ground.

But where do I connect the neutral at the pump switch?  I only have two posts (both hot) + a ground post to connect to.  Reason for my question: I've seen houses wired with 2 hots and a ground coming into the main service panel.  The subpanel idea looks like the same thing but on a smaller scale.  No?

There are so many things you would have to do to make this safe and to code it will be far easier to just run a new 10 gauge underground-rated line out to the pod.  Won't be cheap though.

<span style="line-height: 1.4;">I've seen houses wired with 2 hots and a ground coming into the main service panel.  The subpanel idea looks like the same thing but on a smaller scale.  No?</span>

What you are seeing, if this is the main panel being fed from the utility, and there is a meter (within 10') in-between, is not a ground, it is the Neutral.  The Ground is derived from pounding in an 8' rod into the earth. 

I agree with others, go get #10-2 UF (that is direct bury wire) and run a new single pole circuit to the Pod.

It would end at the sub panel.  What I heard you ask is that could you install a sub panel at your well, then put breakers there to serve both the well & POD.  The answer is yes, if you size everything correctly.  You would have a breaker in your main, sized to protect the wire to the sub panel, then in the sub panel, a breaker for the pod & a breaker for the well.  The POD breaker would be 30A single pole, the well double pole of whatever size you need.  Mine at home is 30A. The neutral would not run to the pump, only the pod.  It has been a while since I did my wiring, would have to go back & consult the books to verify exact requirements.

I work on the utility side of the electric industry, so that is my area of concentration.  As a consequence, I learn quite a bit of the customer side of the meter, enough to seek out the right answers, but not enough to be second nature.

Electricity is fun, as long as you keep it in the wires.