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Old 07-13-2013, 07:22 AM   #1
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HOT Neutral


Drawing "A"
http://microlightstore.com/lamp_and_...t-jumpered.jpg

Drawing "B" http://microlightstore.com/lamp_and_...e_jumpered.jpg


Drawing "A" is about what I was attempting to understand in my previous thread where I muddied up the waters with a too wordy (not that this is not too wordy and partially technically incorrect post, about why an appliance can become HOT after dangerously and illegally jumpering a neutral terminal on a receptacle to the ground screw, in order to complete a circuit that's not workig due to an OPEN neutral.

The first thing in that muddied post was a statement about my understanding of how an OPEN Neutral can become hot, just as Point "A" in Drawing "A" is HOT. No voltage is dropped across the load (lamp) because of the lack of current flow, so there is full source voltage from the HOT side of the receptacle, thru the hot side of the lamp cord, thru the lamp resistance (the Incandescent light bulb), then continuing on via the lamp cord neutral, and on (internally) to the receptacle's neutral post and on to Point "A" in the drawing. I was detailing this screnario in case I was wrong about any part of it, while figuring someone would correct me if so. However, I do know that it's correct now, because I set this same configuration up on my workbench and put a voltmeter (also a clamp-meter for xtra kicks!) to it - measured 120vac from Point "A" to Ground.

Now on to what I really wanted to understand in my original post titled:
Hot appliance due to jumpering receptacle neutral to groud screw . I wanted to understand exactly how an appliance becomes HOT after jumpering the netural to ground screw at a receptacle, because I occasionally troubleshoot electric problems, mostly in mobile homes - basic stuff - and based on some of the stuff I've seen so far, I won't be surprised to run across this situation one day, at least in one particular trailer park. In other words, if/when I do run across a hot appliance one day, I wanted to know/understand what one of the causes could be.

In Drawing "B", I was figuring this configuration was what was meant by an appliance becoming HOT after jumpering a neutral to ground screw on a receptacle. This configuration was my interpretation of MTN REMODEL LLC'S post from an older, unrelated thread, but I should have asked for MTN REMODEL's permission to use his post....because it turns out that as I interpreted his post (Drawing "B", which is the experiment I set up on my workbench), the lamp case does not get HOT after adding the jumper from Neutral to Ground. I'm not saying MTN REMODEL was wrong, I'm saying my interpretation of his mention (the jumpering causing a HOT appliance) was/is, no doubt, not according to the acutal circumstances of his prior experience.

Anyway, all this has led me to my work-bench experiment, which has helped to drive home how an OPEN Neutral can be HOT, as well as how an appliance can become HOT. Best for relative newbies like me to assume everything's HOT, me thinks (when troubleshooting, etc.). The appliance (the lamp in my experiment) did not become HOT, however, in my version of the jumpered Neutral, and I believe I can explain why it did not - please correct me if I'm wrong.

The current returning from the lamp reaches the receptacle neutral terminal, then down the jumper to the ground screw, then on to the bare copper ground wire and back to the source, completing the circuit. Since there is the completed circuit thru the lamp and on back to the source, all the voltage is dropped across the load (lamp), and there is nothing left on the neutral side of the circuit to find its way to the lamp case.

Don't mean to be so wordy, but it helps to put it in my own words and then ask for confirmation (or not). Please correct me for anything you find wrong in this post (and I'm sure you will , assuming that this post makes more sense than the original one, if you've seen that one), or if you have anything to add to this one...

Happy weekend!

Ducky

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Old 07-13-2013, 07:53 AM   #2
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HOT Neutral


I don't really follow your post. The definition of a "hot" appliance case is that the case is maintained at a voltage above "ground". This happens if the hot leg contacts the metal case, which can occur if the insulation on the hot wire frays, or some internal component of the device comes loose and contacts the case. Once the case is contacted by any hot wire, the case will become energized at 120 volts, or 240 volts, depending on the circuit voltage. This has nothing to do with an open neutral or faulty ground, if the hot water touches the case, the case gets energized.

Even if you have a perfectly functioning neutral, the case is still hot. If your ground wire is intact, current will flow from the case along the ground wire, and if the fault is bad enough, you will trip the breaker. If it is only a small hot wire (say one strand of a stranded hot wire comes loose) touching the case, the resistance of the wire will limit the current flow, and you may not trip the breaker. In that case, you can certainly get a shock by touching the case, since it is at 120 or 240 volts, and you are at ground potential, so if you are sufficiently grounded when you touch the case (you have wet hands and you are touching a grounded pipe for example) you will feel current flow through you because current will always flow through a device (you) inversely proportional to the resistance of the device. If you are dry and not well grounded, you will probably feel nothing, since human resistance is something like 1500 ohms dry.

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Old 07-13-2013, 11:01 AM   #3
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HOT Neutral


Well the neutral will always be hot if the lamp was on open or not... And the shock from the neutral is usually worse then from the hot....



The old 3 prong dryers and etc used the ground to run the controls and was a problem ... That is one reason the now make U put a 4 prong in so the neutral carries the 120 v and not the ground
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Old 07-13-2013, 12:06 PM   #4
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HOT Neutral


Quote:
Originally Posted by Philly Master
the shock from the neutral is usually worse then from the hot....
Why is that?
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Old 07-13-2013, 12:08 PM   #5
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HOT Neutral


Ohm's Law
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Old 07-13-2013, 12:12 PM   #6
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HOT Neutral


Quote:
Originally Posted by Philly Master
Ohm's Law
Lower resistance on the return path because its past the load?
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Old 07-13-2013, 12:15 PM   #7
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HOT Neutral


And the concept that on the neutral you are more than likely in series ...unlike on the hot you re more than likely in parallel
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Old 07-13-2013, 12:23 PM   #8
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HOT Neutral


I think I get it - if you gt bit on the hot side it's likely because you shorted the circuit in the same way as the load. On the neutral it's likely because you completed the neutral circuit. Is that right?
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Old 07-13-2013, 08:41 PM   #9
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HOT Neutral


I think that's what he saying (not sure why)

The only way (I can think of) to get shocked by a Neutral, is if its broke/cut, load on the circuit, touch the neutral and ground.

Not sure of the difference between that and touching hot to ground.....
120 jolts is 120 jolts

not saying ... just saying
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Old 07-14-2013, 06:51 AM   #10
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HOT Neutral


Quote:
Originally Posted by Philly Master View Post


The old 3 prong dryers and etc used the ground to run the controls and was a problem ... That is one reason the now make U put a 4 prong in so the neutral carries the 120 v and not the ground

This is untrue, older 3 wire dryers used the NEUTRAL as a ground, not the other way around. Also, all dryers contain a 120v motor, only the heating elements are 240v.
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Old 07-14-2013, 06:57 AM   #11
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Quote:
Originally Posted by Philly Master View Post
And the shock from the neutral is usually worse then from the hot....

AC current is alternating, it is the same result whether you receive a shock from the supply side or the return side.
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Old 07-14-2013, 08:27 AM   #12
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Quote:
Originally Posted by stickboy1375

AC current is alternating, it is the same result whether you receive a shock from the supply side or the return side.
I dont fully understand this yet myself but i have read EC's on other forums say the same thing - that shocks from neutral hurt more. The way I get my is that if you were to cut the wire on either the hot or neutral side and grab both ends then you are in series with the load. If you were to grab bare wire on both the hot and neutral then you are parallel with the load. If in series then you are conducting full current. If in parallel you are sharing the current with the load. For some reason I don't yet get, it seems that if you are zapped by the neutral only then it is likely that you are in series but i don't fully understand why. Maybe it has something to do with the ECG providing a better path.

Like I said - I'm trusting it until I can reason it out and don't yet understand it fully.
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Old 07-14-2013, 08:40 AM   #13
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I dont fully understand this yet myself but i have read EC's on other forums say the same thing - that shocks from neutral hurt more. The way I get my is that if you were to cut the wire on either the hot or neutral side and grab both ends then you are in series with the load. If you were to grab bare wire on both the hot and neutral then you are parallel with the load. If in series then you are conducting full current. If in parallel you are sharing the current with the load. For some reason I don't yet get, it seems that if you are zapped by the neutral only then it is likely that you are in series but i don't fully understand why. Maybe it has something to do with the ECG providing a better path.

Like I said - I'm trusting it until I can reason it out and don't yet understand it fully.
This is just like saying, wow it was 120 degrees out yesterday, but only 110 degrees out today, its still hot outside... And if anything, they only seem to hurt more because you were not expecting to get hit off the neutral. To say it actually hurts more is impossible to prove. Its actually the stupidest comment i've ever heard.
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Old 07-14-2013, 08:50 AM   #14
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HOT Neutral


Quote:
Originally Posted by stickboy1375

This is just like saying, wow it was 120 degrees out yesterday, but only 110 degrees out today, its still hot outside... And if anything, they only seem to hurt more because you were not expecting to get hit off the neutral. To say it actually hurts more is impossible to prove. Its actually the stupidest comment i've ever heard.
I'm not promoting it - just trying to understand why several EC's say it. There is either something to it or its cuz Bigfoot scared them causing them to knock over the tripod used to photo Nessie.
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Old 07-14-2013, 10:40 AM   #15
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HOT Neutral


There seem to be some odd ideas in this thread. Specifically, the notion that touching the neutral is going to produce the same shock as touching the hot wire. I think the difficulty lies in lack of precision about the exact scenario, so let me break down some common scenarios, and let's see if my analysis is correct.

1. The device is off (switch is off), but the breaker is on. You touch an uninsulated portion of the hot wire upstream of the switch. You touch nothing else, and you are standing on dry concrete, wearing typical footwear. What happens? The hot wire is at 120 volts potential relative to ground. You are poorly grounded, meaning there is likely at least 5000 ohms of resistance between the 120 volt hot wire and ground. By Ohm's law, you will feel V/R amps, in this case 120/5000 = .024 amps (24 milliamps). This is certainly enough to be felt, but very unlikely to kill you. Note there is zero current flowing through the device in this case, but you still got a shock.

2. Same scenario, but you touch the neutral wire. There is no current flowing through the neutral, and it should be at close to zero potential relative to ground, since the neutral is grounded at the panel. By Ohm's law, you receive 0/5000 = 0 amps of current, at zero voltage, so no shock.

3. Same scenario as 1, except you are well grounded, i.e. you are holding onto a grounded copper pipe in the house. You touch the hot. Now there is only perhaps 1000 ohms of resistance, possibly considerably less. The amperage going through you is 120/1000 = 120 milliamps, definitely going to feel this, and it could kill you. Note that if you touch the neutral only, you still should receive no shock at all, since the neutral is at zero potential.

4. The device is operating normally. You touch the hot wire, and just as in scenario 1, you will receive a shock. Note that you are in parallel with the load, which is drawing normal current. This is totally irrelevant to the shock you receive, as the amperage going through you is still based on Ohm's law, and the voltage drop across your body is still 120 volts, and your resistance has nothing to do with whether the device is operational or not. In the case of an operating device, the neutral has a small amount of voltage potential, equal to the voltage drop along the neutral wire between the device and the panel. The voltage drop is easy to calculate using Ohm's law. Since V/I = R, V = I x R, so if your device is running at say 10 amps, and the wire has a resistance of say 0.1 ohms, total voltage drop = 10 * 0.1 = 1 volt. The shock you would receive off the neutral would be V/R = 1/5000 = 0.2 milliamps, and you would likely not even feel it.

5. Suppose the neutral is broken off at the device. You flip the switch, nothing happens. You touch the hot wire and are grounded. You get a shock same as in case 1. You touch the neutral and are grounded. No shock, since the neutral is at zero potential (it is still connected at the panel). Suppose you grab the hot with one hand, and the neutral with the other. In this case, you are a series load, and the current will flow from one hand, across your chest past your heart, and to the other hand, then onto the neutral and back to ground. The current will be equal to the voltage drop (120 volts) divided by the resistance. Resistance in this case is going to be 1000 ohms or less, since resistance is entirely due to your body. If your skin is moist, or you were sweating, resistance will be much lower. The current flows directly across your heart, and this is serious trouble. The danger comes entirely from touching the hot wire, since the hot is at high voltage potential relative to ground.

My conclusion is that the neutral wire by itself is relatively safe to touch (NOT THAT I AM RECOMMENDING THIS), whereas the hot is never safe to touch. The fact that the neutral is a current carrying conductor is irrelevant, the only thing that is important is the potential difference (voltage drop) between the current carrying conductor you touch and ground. Unless the neutral is at above ground potential, I see no way you are going to get a shock by touching it. There are situations where through various conditions the neutral voltage is raised, and in this case the neutral could give you a shock. But I cannot see any merit to the claim that the neutral will give you a shock simply because it carries current.

For those looking for a history of grounding, and a more in depth discussion about problems associated with two prong (ungrounded) outlets, see the following article by the Peavey amplifier company, that discusses grounding safety, pseudo grounding, the history of grounding in the U.S., issues associated with inadvertent swapping of the hot and neutral wires, and several other interesting issues as they apply to electronic devices.

http://www.peavey.com/support/techno...hockhazard.cfm

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