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Topic Closed240V stepped down to a 120 leg
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Luv2Q View Drop Down
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Posts: 309 		Direct Link To This Post Topic: 240V stepped down to a 120 leg
    Posted: 18 Nov 2014 at 9:49am
Electricity persons, I need your help.  Please!

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 ..
John & Teri
Tundra 5.7L V8 / RP 180
E2 WDH / Integrated controller (POS) replaced by Tekonsha P3
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Posts: 611 		Direct Link To This Post Posted: 18 Nov 2014 at 10:57am
I am not an electrician, but the short answer is yes, you can.  But things to consider --You may need a circuit breaker on the 120 leg to the pod.  And a ground fault thingy.  You don't want to turn off the power to the pump with a problem in the pod.  And you will probably want to put all that in its own box to keep weather out.   I would vote for getting professional advice.  That way you have someone to call if there is a problem.
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Posts: 767 		Direct Link To This Post Posted: 18 Nov 2014 at 12:40pm
To ground?  Technically, it'd work, but I wouldn't do it.  I'm not really fond of intentionally running current through an unshielded wire, and the ground wire is occasionally connected to the water system to reach earth - fine for a failsafe, but I'd rather not for regular use.

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.
Craig :: 2009 RP171 towed by a 2017 F150
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Posts: 633 		Direct Link To This Post Posted: 18 Nov 2014 at 1:06pm
Originally posted by Outbound

To ground?  Technically, it'd work, but I wouldn't do it.  I'm not really fond of intentionally running current through an unshielded wire, and the ground wire is occasionally connected to the water system to reach earth - fine for a failsafe, but I'd rather not for regular use.

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. 
Sean, 2011 Rpod RP-173,2009 Jeep Liberty Rocky Mountain Edition
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CharlieM View Drop Down
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Posts: 1797 		Direct Link To This Post Posted: 18 Nov 2014 at 2:26pm
I agree with the above comments. Intentional current in the bare safety wire of a two wire connection is against all codes, and for good reason. If the well is still in operation your best bet would be to run a new two conductor plus ground cable from your main breaker panel, protect it with a 30A single pole breaker, and install the standard 3 prong RV socket near the parking spot. For a long run like 100 feet I would use #8 or #6 AWG wire. Do it right and do it safe. 
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Posts: 611 		Direct Link To This Post Posted: 18 Nov 2014 at 4:34pm
I didn't know that one could do 220 without a ground wire.  So that pump circuit was installed some time ago?   
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Posts: 1797 		Direct Link To This Post Posted: 18 Nov 2014 at 5:36pm
It sounds like the 240 volt circuit is installed properly: two hot wires and one bare safety ground. The problem is there's no neutral, which is required for the 120 service. 
Charlie
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Posts: 767 		Direct Link To This Post Posted: 18 Nov 2014 at 5:45pm
Originally posted by john in idaho

I didn't know that one could do 220 without a ground wire.  So that pump circuit was installed some time ago?

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.
 
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Posts: 633 		Direct Link To This Post Posted: 18 Nov 2014 at 5:52pm
Originally posted by Outbound



Originally posted by john in idaho

I didn't know that one could do 220 without a ground wire.  So that pump circuit was installed some time ago?

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.
 



Most electric baseboard heaters are 220 as well.
Sean, 2011 Rpod RP-173,2009 Jeep Liberty Rocky Mountain Edition
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Posts: 309 		Direct Link To This Post Posted: 18 Nov 2014 at 6:49pm
Thank you all for the constructive & helpful comments.

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

One other option that I don't believe was mentioned (or if it was I didn't quite catch it):  From the pump switch, run 2-wire + ground 220 to a subpanel.  From the subpanel, with a 120V 30 amp breaker, run a black (hot), white (neutral) and bare ground to a 30 amp outlet. All using appropriate wire size, of course, as suggested above.

Edit: After reviewing earlier posts, I believe CharlieM suggested this very thing. Thanks, Charlie.

How does this sound?  I'd still need to be cautious on what I run in the Pod in case the irrigation pump was operating.  That pump BTW is on a 30 amp breaker so I'll be upping that to 50 or 60; the existing pump wiring will handle it.

So, what do you think? Right track, or am I off in the weeds, lost as usual? Confused  Again, thanks everybody!
John & Teri
Tundra 5.7L V8 / RP 180
E2 WDH / Integrated controller (POS) replaced by Tekonsha P3
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