Converting 230v to 115v receptacle

[Fritzread]

I want to convert an existing 230v appliance receptacle to a pair of 115v receptacles. I expected to find two hot leads and a neutral, but when I opened the box I found two hots and a bare ground wire. This is an older house (ca 1902) with some knob and tube, some recent bx rewiring, and some of uncertain age. Most normal circuits appear ungrounded, with only a hot and a neutral, but some of the newer circuits are three-wire, though I don't know if the ground is good or not. In addition, in most of the older lighting circuits the neutral is switched rather than the hot leg.

So, the immediate question is: how do I convert the receptacle from 230v to 115v? The bigger question: does the present setup sound unsafe? Should I have the whole place rewired?

Thanks!

[Wgoodrich]

It is absolutely unsafe to use a bare wire as a current carrying neutral conductor. You can not split the branch circuit that you desire. You will need to install a new branch circuit with a white wire in the cable to use 115 volts. DON'T DO IT.

If you truly have grounded [aka neutral] conductors switched then you have an unsafe house. Problem here is that I question that is true. Often times a white wire in a three or more switch system uses the white wire as an intermittent hot wire. Switch legs in the past were allowed to use the white wire as an intermittent hot wires on switch systems only. Then again the NEC still allows white wires to be used in a single pole switch system or a white wire feeding power to three way or more switch systems. Then the NEC also allows a/c units or motors to use a white wire as a hot wire because no neutral would be used on that type branch circuit.

I would have a qualified electrician take a look at your house and cofirm what you believe before you decide on a complete rewire. If what you say is true then you have major concerns for safety if grounded legs 115 volt or neutrals 220 volts are switched.

Be careful

Wg

[Fritzread]

What are the specific safety concerns that come with switching the neutral wire? I've scheduled an electrician to come look things over; his initial reaction, and that of an electrical engineer I sometimes have worked with, is pretty much the same as yours: yes its unsafe. But they haven't said just how or when its unsafe.

The house has been this way pretty much forever, without any apparent problems, and both the electrician and the electrical engineer tell me it used to be quite common, the normal way of wiring houses. They weren't the least bit surprised.

I'd like to understand this a bit better, so I know just how worried to be, and so I know how I should be wiring things when I replace old switches. Do I keep things as they are, with the switch on the neutral side, or rewire as I go? If I can't afford to rewire the whole place now, what do I do in the interim? What kind of risk am I taking?

Thanks.

[Wgoodrich]

Chances are all that would need to be done is to open each switch and change the wiring inside the box so the hot is switched and not the neutral. Then open each receptacle and light fixture box and ensure that the hot wire is connected to the brass screw of the receptacles and not to the silver screw of the receptacle then in the light box the hot wire is connected to the black wire of the light and not the white wire of the light. This means you would have to shut off the main breaker in your panel shutting off the entire home. Then go to the farthest room and open each receptacle and switch and light fixture. Take an electronic voltage tester and touch the positive test lead to the hot wire. It should buzz telling your that is the hot wire. If you have a sweep meter style voltage tester then drive a pipe into the ground outside and run a single wire through your house to the location your are testing. Test from that temporary test lead to the hot wire. It should show voltage reading on the hot wire an no voltage reading from the neutral wire if no load is connected. Just make sure the wires are disconnected and hanging in open air when you test. Then Connect the hot wire to the brass screw and the white neutral wire to the silver screw of the receptacles. Do the same in the switches. Use your temporary test lead to earth. Test to find the hot wire in the switch and connect the hot wires to the switch and the neutral wire that reads no voltage to that test pipe connect together wire wire nuts not connected to the switch. Make sure your light fixture is unwired during that switch box test. Then in the light box again use the temporary test wire to find the wire in that light fixture that measures voltage to the black wire of the light fixture.

If you have a switch that only has two insulated wires in it then you must go to that light fixture it controls and confirm that the white wire going to that switch that only has to conductors coming from one cable in that switch box and the black wire coming from that light switch to that light fixture box is connected to the black wire of the light fixture only and not the white wire if the light fixture.

Polarity is where the hot is connected to where the white neutral wire is connected. This can energize the metal frame of your equipment if a failure of insulation is experienced or you have an older appliance plugged in.

The major concern for safety when switching a white grounded leg p[aka neutral conductor] is that you have a loaded wire seeking a return path back to the transformer. The best method of explaining the dangers involved concerning a white grounded leg [aka neutral conductor] or true neutral conductor is in my mind easiest to paint a picture as follows;

Picture the loaded return path to the transformer [open white grounded leg or neutral] as a ballon. When you blow the air into the balloon no reaction other than the balloon expands. Now you have a balloon full of compressed air. Picture this compressed air as an open grounded leg or neutral. Now if you let the air out gradually your ballooon just gets smaller releasing that pent up pressure of compressed air. This would be like a connected grounded leg or neutral that has a complete return path to the transformer. The loaded grounded leg or neutral would just return the unbalanced load to the transformer as it is present dissapating any pressure thus no reaction just like the balloon.

Now picture letting the compressed air out of that blown up balloon suddenly by punturing the balloon with a pin or needle. You would experience a boom from that rapid release of that air.

A loaded grounded leg or neutral has what is called an inrush of current when that loaded grounded leg or neutral suddenly finds a return path to the transformer or any location that you can pass this current seeking a path. The earth can be that path to release that loaded grounded leg or neutral conductor. When this inrush happens the reaction is much like the balloon bang sound. The inrush rapidly reduces the pressure of this open grounded leg or neutral just like when the baloon explodes. That rush of current unloading causes a massive increase of both voltage and current until the load is equalized back to normal conditions. This is why a loose neutral will create an experience of an overly bright light bulb. The loose neutral is working some times and not working some times causing this inrush of current which causes the light bulb to over work dumping the volage or current suddenly on the load side of the light bulb. The key point is you have an open conductor on the load side of a product such as a motor or light bulb. This creates that inrush of current or voltage when that open conductor on that load side of that product trying to do work finds a path to unload. This inrush creates a surge of power that can and will back feed up an equipment grounding conductor much like a surge of power like lightening causing the metal cases of your appliances to become energized.

The above explaination you must understand happens in a fraction of a second. However if you are in that path or completing that return path to ground [center tap of hte transformer or earth] then that rush of current can and will kill a living being.

There is more that happens but the laymen's discription above is my attempt to provide a picture in your mind the safety hazards that exist when you have a loaded open grounded leg or neutral conductor [white or gray wire]

You don't really have to rewire your home pulling new wires. YOu just have to ensure proper polarity and that no grounded leg or neutral conductor is being opened by a switch. You can start at one end of your home and do as discribed above and make your own home safe if you have some knowledge in electricity.

Let us know how you come out. Hope you enjoyed the picture I tried to paint in your mind and hopefully shed some light to the knowledge you seek.

Hope this helps

Wg

[Fritzread]

Thanks so much for the reply. It sounds like I have a winter project ahead of me. I'll let you know how it goes.

[Wgoodrich]

Good luck with your project

Wg