Tapping 120v from 220v

[ultrarunner]

This might explain...

Fixed appliances on three-wire circuits:

In the USA, the cases of some ovens and clothes dryers were grounded through their neutral wires as a measure to conserve copper during the Second World War. This practice was removed from the NEC in the 1996 edition, but existing installations may still allow the case of such appliances to be connected to the neutral conductor for grounding.

You were correct... 3-wire circuits

 

[BobRip]

This might explain...

Fixed appliances on three-wire circuits:

In the USA, the cases of some ovens and clothes dryers were grounded through their neutral wires as a measure to conserve copper during the Second World War. This practice was removed from the NEC in the 1996 edition, but existing installations may still allow the case of such appliances to be connected to the neutral conductor for grounding.

You were correct... 3-wire circuits

I always wondered why they did that. I built my house in 1995 and used this older practice. I did fully understand what they were doing at the time and would not have done it if I did.

 

[carpenter383]

This isn't related to using 110 off 220, but what I don't understand is the neutral wire is connected inside the breaker box with the grounds, so aren't they both doing the same thing? How does the neutral wire take current?

 

[CurlyDave]

Around here, the neutral wire is grounded inside the breaker box and a common wire is run to a grounding rod.

The neutral wire is also grounded at the power pole or transformer.

A long time ago, I learned not to ask why this is OK, but just do it like the book says, and the inspector will pass it.

 

[Mike058]

Imagine you have a shop in an outbuilding. The cable that runs to the breaker box in the outbuilding is 3 conductor (black, red, white) plus a bare grounding wire. You have a saw that runs on 220 volts and draws 10 amps. You have one light bulb that is 110 v and draws 1 amp. The saw is hooked up to the black and red wires, but the light bulb is hooked to the black and white wires. Leave the light off for a moment and turn on the saw. Ten amps are flowing through the black and red wires. The load is balanced and no current flows through the white or bare grounding wire. Turn the saw off and turn the light on. One amp is now flowing through the black wire, but also through the white wire. No current is moving through the red or bare grounding wire. Leave the light on and turn on the saw. Ten amps of current is now flowing in the red wire. Eleven amps is flowing through the black wire and the white wire is handling the difference of one amp. Nothing flows through the bare wire. This is the case all the way back to the service entrance. Now if the white wires and bare grounding wires were connected together in the panel in the shed, you'd have a real problem. Because that one amp that was confined to the insulated white wire is now going to be shared between that white wire and the bare grounding wire that is suppose to be bonded to every piece of metal that surrounds the wires and your plumbing to boot.

The amount of current that would actually leak into the grounding system would depend on the resistance(or reactance to be really technical) of the wires, the amount of unbalance in the system and I'll bet some other stuff too.

Why is it ok (even required) to bond the neutral and grounding wires in the service entrance? I don't know. Haven't figured that out yet. Just know it works.

Bottom line: don't connect neutral and bare wires together any place but at the service entrance.

 

[MikeD74T]

Mike058, Nice explaination.
The neutral/ground imbalance has reared it's ugly head on two dairy farms I worked on in the 60's. In one case milk production dropped off significantly during the winter. Owner couldn't figure out why until he reached in to clean a waterbowl and got hammered. All 75 waterbowls in the barn were energized. Cows standing on concrete with their bare feet got zapped when they tried to drink thus were becoming dehydrated. Power Co insisted it was barn wiring. Electrician couldn't find any source then it suddenly disappeared. Later a lineman confessed that they fixed a bad neutral a mile up the road. The unbalance was coming into the farm neutral & ground. Water pipes made up the ground & cows became the shortest path to earth.
The other farm had cows electrocuted on two occasions from bad neutral. Power Co paid for their cows. That farm is currently milking 1300 cows & although they get power from the Power Co they are not connected to the neutral. Have their own engineered earth ground system.
If the well house in this thread were mine, I'd bolt AND solder a good copper clamp to the well casing & wire my bulb/outlet neutral/ground to it - but then I'm not an electrician. MikeD74T

 

[TheGoose]

Some interesting responses to this thread.

First off, the 110v is not the problem. It's the neutral, or a lack of one, that is the problem. You can come off of either leg (each leg is 110V) to get your voltage, but without a return leg or neutral it won't work. There are some ways to jerry-rig this but they would all either violate code or compromise safety.

One other thing to consider...if you have a jet pump you can convert it to 110V most likely. If it is a submersible pump no dice, they can't be converted. If you do have a jet pump look on the motor and see if it is convertable, most of them are. This is of course assuming you have a big enough wire to supply the extra amps/distance needed for your shed.

A word of caution: if you do tie into your pump supply it could create problems. Since the pumps surges when it starts it probably uses most of the capacity of the wire that supplies it. If the wire is 12 gauge (pretty standard), it is only good for 20 amps. A 1-HP pump pulls 8-9 amps when running and double at the start. If it is 110, it pulls 18 amps when running, and surges when it starts. Any kind of problem or overload at the shed and now you're without lights at the shed and water to the house. You could do it in a pinch but I would be very careful about how I set it up so that I could disconnect the shed from the main supply. At the very least you're going to need a seperate neutral. All that work to replace the wire I might would run a larger service to the well/shed and install a seperate panel.

Good luck.

On one of our properties, we have a well with a 220v pump. I want to put a small shed about 100/150 ft. from the well. I would like to put a light and one or two outlets in the shed. Can I tap into the well power and get 120v at the shed?
1. Can it be done? How (white to white and black to black (or red) and where does the 120v ground/bare wire connect) ?
2. Should it be done? What is the effect on the well pump?

Norm

 

[nap61]

Thanks again for all the replies.
This was never a "do it yourself" project for me. But, I knew the wealth of knowledge on TBN and wanted to get some ideas from the group. I have learned a lot from reading about the problems and solutions that come across this forum. The ones that have really stuck with me are the safety warnings/suggestions that the "pros" who have the experience (sometimes bad) pass on while answering others questions.
It seems that the best course is to run a new circuit from the main to the shed.
Thanks again.

Norm

 

[BobRip]

This isn't related to using 110 off 220, but what I don't understand is the neutral wire is connected inside the breaker box with the grounds, so aren't they both doing the same thing? How does the neutral wire take current?

There is an additional reason for not sending current through the ground. Electrical systems are designed so that no single failure will cause a safety hazard. If you use the ground wire to carry current and it fails then the metal case of a motor or panel can be come electrically hot (voltage is above ground potential). Depending on the unbalance this could kill you or your cows. If you have a separate neutral and ground, either one failing does not cause a hazard.

Back at the panel you do have the neutral and ground tied together, but that panel is also grounded with a wire to a ground rod. No single failure will create a shock hazard.

Before you had grounds, an electric drill case might short to the hot wire and then you would have 120 volts on the thing you are holding. If, on the other hand, the case were grounded then the fuse or circuit breaker would blow.

I hope this helps

 

[captaincrab55]

I used to come across a lot of old 220v electric ranges wired with 2 hots and a ground AND a 110v convenience outlet on the range top... so, at one time, at least in major appliances... it was possible to get 110 from a 220 circuit.

There was a Code change to prevent that and may I say that it was a good change too...