240V Question

[HiPlainsDrifter]

I'm hoping an expert here can clear up my understanding of 240 vs. 120 volt wiring. I'm reading the book Wiring Simplified and there is a statement that is really confusing me.

In describing a 240 volt circuit, it says "If you touch both hot wires, you will be completing the circuit from one hot wire to the other, and you will receive a 240-volt shock. But if you touch only one of the wires, you will be completing the circuit through your body, through the earth, back to the grounded neutral in your service equipment, and you will receive a shock of only 120 volts."

I understand the 240-volt shock from the two wires. What I was definitely not aware of is that I can get a shock from touching just 1 wire in a 240 circuit?? And, if that is the case, can touching just one wire in a 120 volt circuit give a shock? I would think it would have to be, since the single hot wire in a 120 is the same as one of the hots in 240.

I'm trying to just get a better handling on AC wiring, which I don't have very much experience with.

Thanks,
Travis

 

[rockwithjason]

the short answer is yes you can get a shock from just touching the hot wire in a 120v circuit. you can also get a shock from the neutral wire in certain situations.

 

[Steevo]

Wear good rubber soled shoes and touch only the one wire, and you'll barely feel a thing . . .

 

[rockwithjason]

i was trying to stay out of the whole ground path discussion

 

[cnttxmdc]

i was trying to stay out of the whole ground path discussion

The first time I clicked on this thread and saw the responses already posted I thought to myself "back... away... slowly...."

 

[wyliesdiesels]

I'm hoping an expert here can clear up my understanding of 240 vs. 120 volt wiring. I'm reading the book Wiring Simplified and there is a statement that is really confusing me.

In describing a 240 volt circuit, it says "If you touch both hot wires, you will be completing the circuit from one hot wire to the other, and you will receive a 240-volt shock. But if you touch only one of the wires, you will be completing the circuit through your body, through the earth, back to the grounded neutral in your service equipment, and you will receive a shock of only 120 volts."

I understand the 240-volt shock from the two wires. What I was definitely not aware of is that I can get a shock from touching just 1 wire in a 240 circuit?? And, if that is the case, can touching just one wire in a 120 volt circuit give a shock? I would think it would have to be, since the single hot wire in a 120 is the same as one of the hots in 240.

I'm trying to just get a better handling on AC wiring, which I don't have very much experience with.

Thanks,
Travis

If you touch a grounded object(as in connected to the ground or neutral bus in your electrical panel) with one hand and a hot wire in the other, yes u can get shocked.

Ive touched hot wires before and have not been shocked because I was not grounded some place on my body and my boots are electrically insulated, so i did not complete the circuit.

Now, the part about the electricity returning through earth is pretty rare as the earth has a pretty high resistance. Merely standing on dirt, with shoes on, creates a very high resistance path so u may feel a light shock but most likely none at all because of the high resistance.

 

[ddawg16]

240 VAC is actually 2 120Vac lines.

If we are talking about the power coming into your typical house....you have 3 wires....one is the neutral...the other 2 are 120Vac.....but because those 120 Vac lines are 180 degrees out of phase relative to each other....you get 240 Vac if you measure across them.

If your standing on an isolated pad (no electrical connection to ground), you could touch either wire and not get shocked....but if you touch both at the same time....your going to get shocked.

If your grounded and you touch either wire...your going to get shocked.

I find that it's best to not touch wires that are energized. I don't like getting shocked.

 

[abnorm]

First question in five years ?......ummmm Welcome to the forum

 

[ez-duzit]

Simple--DON'T TOUCH HOT WIRES, EVER!

 

[HiPlainsDrifter]

Thanks a lot for the help. I wasn't asking because I want to be in the business of touching hot wires, or because I want to work any less carefully-- it was just a case of "inquiring minds want to know".

Everything about 240v being 2 120v hots out of phase with each other makes perfect sense, it only surprised me because the conclusion I had to come to was that touching a single 120v hot wire, while grounded through the earth, could theoretically shock a person (depending on the particulars of where you're standing, wearing, etc.) Makes perfect sense now.

Thanks again. --Travis

 

[theoldwizard1]

Bare feet (or even sandals) and electricity are not a good combination.

 

[PowerMan]

Thanks a lot for the help. I wasn't asking because I want to be in the business of touching hot wires, or because I want to work any less carefully-- it was just a case of "inquiring minds want to know".

Everything about 240v being 2 120v hots out of phase with each other makes perfect sense, it only surprised me because the conclusion I had to come to was that touching a single 120v hot wire, while grounded through the earth, could theoretically shock a person (depending on the particulars of where you're standing, wearing, etc.) Makes perfect sense now.

Thanks again. --Travis

Actually, 240V is both ends of the SAME circuit in the power company transformer (usually on a pole outside), the "winding" or coil of wire in the transformer that is the secondary side of a much higher line voltage going down the power poles (usually 10-12kV). That transformer winding is producing 240V from one end to the other, which are the two "hot" leads brought to your house. But that winding is also "tapped" in the middle and that middle point is connected to ground at the pole, which becomes the Neutral wire that is run to your house. So one end of the transformer to Neutral is 120V, the other end of the transformer winding to Neutral is 120V as well, then one end to the other end is the full 240V. The reason why you get shocked by touching either end (as a "120V" hot wire) is because you are completing that circuit to ground, the "other end" of that half of the winding.

 

[J Persons]

I once bought an investment property, (rent house) where the previous owner had installed a 240V window A/C, plugged into a 120V circuit that had been rewired to provide 240V. They had removed the white from the neutral buss and connected it to the other hot buss at the fuse panel. They also used the ground wire as the neutral, but it just went to ground. I called an electrician to run a new circuit, explaining to him that it wasn't me that wired it up. He just sort of laughed, saying that fixing things like this was keeping him in business and profitable.

 

[wyliesdiesels]

I once bought an investment property, (rent house) where the previous owner had installed a 240V window A/C, plugged into a 120V circuit that had been rewired to provide 240V. They had removed the white from the neutral buss and connected it to the other hot buss at the fuse panel. They also used the ground wire as the neutral, but it just went to ground. I called an electrician to run a new circuit, explaining to him that it wasn't me that wired it up. He just sort of laughed, saying that fixing things like this was keeping him in business and profitable.

Are u sure they used the ground wire for the neutral? A 240v device doesnt need a neutral.

 

[Falcon67]

Are u sure they used the ground wire for the neutral? A 240v device doesnt need a neutral.

That. My 240V compressor circuit uses regular Romex 12-2 w/ground. The white wire is remarked with black ink at both ends - two hot leads and the grounding wire, no neutral required.