115 Volt from 230 circuit?
 

Is it possible to split off a 115 volt outlet from a 230 volt circuit?

You have to change the outlet, then in the breaker box, remove the dual pole breaker and put in a single pole..

That is how I found some wiring in the house. YIKES!!!

Wouldn't that make the entire circuit 115 V?

Yes, it would, but it's the only way you can do it.. You can't split off it...

Believe me, if you could, I'd be doing it myself.. I have to install a water system, and I don't have 115 for the pump and carbon tank.. but I do have a 230 outlet for the well pump... Sadly no way to split it.. I have to run another cable and wire in a new breaker and outlet.. .

They do however make adapters that you can plug into a 230v outlet that will give you two 115v outlets, BUT, it's either or.. You can't have both 230v and 115v...

If you have 3 wires, 2 hots and a neutral, yes you can take off 120v. You have 240v between the 2 hot wires, and 120v between neutral and either of the hot wires. There's an outlet in my house that does exactly that -- looks like a standard 2-outlet setup, but one outlet is 120v and the other is 240v and takes a slightly different plug.

Of course, whether it meets code, or is workable for whatever you have in mind, are entirely different questions.

There's the problem with it.. It doesn't meet code and it's a really dangerous thing to do... I've already lost one place to a fire.. That's why I said NO.. not possible..

In life anything is possible, but that doesn't mean it's a smart thing to do.. I would never give someone advice to do a wiring job that is not an acceptable practice.. I don't think you'd find any electrician to do it even as a friendly favor.

I plan to spend a few hours running a new line for a new outlet instead of spending 10 minutes to take a really stupid shortcut..

Depends, you can drop a 120 off 240 but make sure you run a separate box and have a 15 or 20 amp breaker. Otherwise you have a high amp wire and it will not trip back to the 240 breaker....James

Making poor connections that overheat and start a fire, is dangerous.

Using wire that's too small and overheats and starts a fire, is dangerous.

Not having proper breakers or fuses on a circuit, is dangerous.

Taking 120v off a 240v circuit, and drawing current that's well within the capabilities of the wiring and the circuit breaker, is exactly what every 120v circuit in every house has always done. It may (or may not; I don't know) be a code violation to do it outside the breaker panel instead of inside, but it's not dangerous.

Electricity is dangerous if you don't know what you're doing, and it's a lot more dangerous if you think you know what you're doing but don't. That's why there are codes; govern yourself accordingly.

I prefer to help him learn, and let him be the judge of what safe and prudent course he wants to take once he's considered all relevant factors.

Lots of ways to rig it, i'll add another possible solution. Use a voltage step down transformer. They are used extensively and are safe, these are not adapters but quality built transformer box with terminal inputs and outputs. One of these would work but it would add a piece of equipment that could fail in the future. Not worth it in my opinion and likely not code for your application.

If it we're me I would change the breaker and wiring configuration to address your water pump application. Easy to do and cheap as well. As SEMI noted, only thing you would need is a different breaker, and a new reciprocal box as the wiring is already in place.

If your not comfortable with wiring stuff please refer to a trained professional, lots cheaper than a hospital visit! Good Luck!

You also have to worry about which leg of the wiring is switched on the breaker.. Could be done right, may not be, and if it's not right and someone goes trying to split off, you may be setting up a real bad situation..

As you note, a lot of this is a bad idea.. unless he's adding another proper breaker after the 230v outlet, which WOULD NOT BE IN CODE, then you're playing with fire... I've never seen anywhere it's within code to split off a 115v leg from a 230v circuit...

Like I said.. I too need a 115v outlet by my 230v... I WILL NOT split off it, because it's not code... I can do any wiring I want, and I do not need a permit or have it inspected, but I'm not going to be doing things outside of code... for the simple reason, code is there to save people from their selves..

As long as the circuit breaker providing the 230V will interrupt both ungrounded conductors there is nothing against the NEC 2014 with doing this. In fact, they provide a picture of exactly what is being in question as an example. Look at Exhibit 210.2 in the NEC.

https://www.inkling.com/read/nfpa-na...ral-provisions

NOTE: You MUST use a grounded neutral conductor for the 115V circuits. Please DO NOT use the receptical ground wire in the load circuit

Your link lays it out pretty clearly, and should make it easy to get it done safely. Here's the part on multiwire branch circuits in a nice neat PDF:

http://mjobee.com/projects&news/nec%20art%20210.4.pdf

OK.. Thanks ya'll.. I stand corrected. I've been looking for this myself for a while, and everything I had found said it wasn't code... and now you saved me a lot of work running a new line... That is, so long as what is installed now is correctly wired..

Don't forget to check local regulations as well. Every area has it's own nuances.

Also this requires a modern 2-pole breaker, it is not code to do with an older screw-type fuse box of a pair of breakers with the handles connected.

I'm totally unregulated... I can build a whole house without pulling a permit or any inspections... so long as I don't need to dig a well or install a septic, I'm golden..


I still want to keep within codes for the simple fact of I don't want to burn the place down, of give myself a perm... plus it makes reselling if need be a lot easier when everything was done right.

One thing to remember is how many amps does it take to through the breaker. A regular 115 plug is rated at 15 amps so anything more than 15 amps is dangerous.

That is why I said "depends" In Simi-steadings case you could make the circuit (if heavy enough) your main into a box and make 1 240 and 1 or 2 120 circuits for other use. I am not an electrician but I have the code book and do all my own wiring. New construction and rewiring. Learned a lot from my B-I-L, his DAD was an electrician but he passed away before I married their daughter/sister. I have to have all my wiring permitted and inspected....James

yes it is possible all the 120 volt circuits in your house now are a splitting of a 240 volt system,

a little more info would help to inform you on how to do it for your application,

Taking 120v off a 240v circuit, and drawing current that's well within the capabilities of the wiring and the circuit breaker, is exactly what every 120v circuit in every house has always done. It may (or may not; I don't know) be a code violation to do it outside the breaker panel instead of inside, but it's not dangerous.


Slow down. There is a reason it isn't done. 230 volt is taking the two end taps (A & C) of the mains transformer. 115 is taking one or the other end tap and the center tap (B)which is also grounded.

If the wires are not terminated and have no load, then it is
A>B = 115
C>B = 115
A>C = 230

Once you remove the load (a toaster for example) from the point where the ground is made, and stick it on the end of a long wire, the wire which is supposedly neutral (at ground potential) shifts a few volts. If the load isn't double insulated, you can get zapped. If you only have three wires to work with, ALL THREE WIRES have to be considered hot. If you have three wires PLUS a ground wire, you are a little safer.

There is more, but that is enough for me to not recommend the practice.

Harry, the neutral wire is required to be grounded at the breaker box.

I fully understand that it is attached to a ground buss at the box. The problem is that it ONLY represents a ground level along the wire with no load attached. There are some really odd voltages that can happen in an unbalanced situation.

The voltage can only be as high as the resistance of the wire times the current. If proper wiring sizes are used it will not be significant. In either event it would be no worse than a 115V circuit.

Are you talking about the neutral between the box and transformer?

Thanks for all the info. To me as a non-electrician it seemed logical that a person could split off 115 volts by tapping into one of the hot wires but I hadn't considered the part about tripping the breaker.

As it turns out my friend needs 230 volts so there is no need to reduce it to 115 volts.

Just to show some of the weirdness that can happen when things aren't done to standards:
http://www.city-data.com/forum/house...ting-160v.html

(It doesn't directly relate to the original question buts sheds more light on some of the other issues raised.)

My "licensed" electrician took a light and 2 duplex receptacle off a 230 box meant for my pump. He didn't bother to run a common, and cost me a compressor motor. Of course, he's the same one who introduced me to "3 second toast". But that's another story.

That sounds exactly like what happens when you get a floating neutral (no longer connected to ground). When the person says "checked each leg" he is checking it to ground. With the neutral able to float it was carrying 40V to ground and resulted in the two readings.

Btw that is a cheap power strip if it can't handle 200V to ground.

Correct and correct. Neutral could "float" all over the scale in such a situation.

Now, how about where someone has taken a 115 volt significant load, rocket scientist fashion connected it to one leg of a 230 volt circuit, and that same circuit also has a significant 230 volt load, all at the end of a couple hundred foot run? There will be line drop AND, IIRC, a meter from A to B will show a different voltage than B to C and there will be voltage between B and a true ground lead. I'm not quite sure how a ganged breaker would handle that. An overload on one leg might cause breaker action to trip the other leg, or it might not. I'm thinking that a properly functioning one should have the strength to trip the other, but I've also flipped enough breakers (Typically about 80 per multiplex projection booth flipped twice a day) to know that some breakers are really weak. I just know that I wouldn't take a chance.

I'm not an electrician nor have I played one on TV but. . .

Couldn't you run the 230 into a small breaker box, add a ground rod at the box then put a 115 circuit on a breaker? Assuming the wire and 230 breaker are large enough you could put in more than one circuit.

After all this is what is going on in a large scale here. There's 230V out of the meter to an outside breaker box which I have my pump and some outlets connected and 230 goes out the bottom of the box to the box in the trailer where there are several 115 and a couple of 230 circuits.

You have to carry the center tap of the transformer for the neutral. The transformer windings make that tap half the voltage between the two ends.

A proper system should not conduct any current to the ground. In order to get a 115V circuit the neutral bus needs to be used.

I didn't follow all of this but realize a "ganged" breaker it's not allowed. It must be a two pole breaker that simultaneously trips both legs.

If there is more than a couple volts between neutral and ground something is wrong. Either the neutral is not grounded or the wiring does not meet code.

Ok so you are saying the electric company is doing it wrong when they run power from my outside breaker box to my inside one? Its the very same set up, just using 200 amps instead of 30-50 amps.

You are required to have your ground at the entrance. The ground on the center tap of the pig serves a different function.

Here's the set up. The weather head is on my pole and that goes to the meter box. From the meter box it runs into a breaker box. Then the main lines go out the bottom of the outside box and to the breaker box in the trailer. From there it branches out to all the necessary circuits.

I have a 230 line running from the outside box to the well. If I remove the pump why could I not simply put a box where the pressure switch used to be, use the hot wires as the two legs, the neutral as the neutral and put in a ground rod for the ground and put in two 115 circuits (assuming there are enough amps for them)? It would be the same set up, in small scale, as the wiring to my trailer's box.

Look on your trailer pole. There should be a bare thick copper wire going from the box down the pole to a ground rod driven in the ground. If that is there, and there is a bare fourth wire going to where the pump was, you are golden. Put in a box with a couple of GFI outlets. In your case, putting in a second ground rod wouldn't be needed unless it was WAY away.

what do you mean by "outside box"? Is this the meter or is this a breaker box?

You can use the 230 line and neutral from your breaker box and feed another breaker box. This is done lots of places. I believe you need to carry the ground from the first breaker box to the second and not set a new one but would have to check to be sure of that.

You can swap a double pole breaker for 2 single pole breakers. and size for load. that way if one trips it does not trip the other and you will know which one is giving you a problem.

You can, but not generally a good idea. You can sometimes burn up a motor or damage equipment that way, but more importantly when a circuit doesn't work, most people think the entire circuit is dead and start acting like that is the case.

The way its set up is (required by either the county or the electric company I can't remember which). . .the main feed from the transformer comes into the weather head on my pole and down to the meter box. It goes from there to a breaker box. Then it exits the bottom of the box and feeds into a second breaker box in the trailer.

I don't see why you couldn't do the same basic thing using a 230 line and a second ground rod. After all, all the ground rods in the world are driven into the same ground.

Yes you do the same basic thing. Use a 2 pole breaker and the neutral to feed the other box.