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Posted: 5/20/2021 5:06:07 PM EDT
[#1]
Bump for the now off work crew.
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Posted: 5/20/2021 5:10:41 PM EDT
[#2]
You cannot measure voltage from one point. You can only measure a voltage difference between two points. Asking what the voltage on a single conductor is, without referencing it to some other conductor, is a meaningless question. By convention, the neutral conductor is 0V for convenience because it's the reference point. You could call it anything you want...0V, 1000V, 1MV...the reference point is meaningless and your other two legs will always be +/- 120V from whatever you fix as the reference voltage.
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Posted: 5/20/2021 5:13:01 PM EDT
[#3]
V = IR
I is the current of the devices using that neural as the return path, and R is the resistance to ground. R is very low so even with current, the voltage will be very low. PS: Unless you have some specialized system, your neutral line will be connected to earth ground just as the ground wire is, but the ground wire does not normally carry any current, so you may see the small voltage when comparing between neutral and ground, depending on the current being carried by the neutral line. An example, 12 AWG wire is 0.001588 ohms per foot. If you have 20A using that neutral, then that's around 0.03 volts per foot from the ground connection. |
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Posted: 5/20/2021 5:30:12 PM EDT
[#4]
Ummm...what? Neutral is a return path for current. Depending on how you tap power, you'll either get 240 or 120. The power delivery is all AC because that's how it's delivered from the power plant.
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Posted: 5/20/2021 5:37:04 PM EDT
[#5]
Quoted: I’m talking about true alternating current “sine wave” pressure voltage. 'Pressure voltage'? heck? |
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Posted: 5/20/2021 5:40:37 PM EDT
[#6]
Voltage relative to what? Ground? Not much. In nearly every setting the neutral conductor is bonded to ground at the first panel after the meter at your residence. At the point of bond the difference is obviously 0V.
If it's carrying current for some reason you can have a slight voltage at one end of the wire far away from that panel equal to the wire resistance * current. The further from the bonding point, the more wire resistance, the more voltage relative to ground for a given current. |
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Posted: 5/20/2021 5:46:04 PM EDT
[#7]
Voltage is a measurement of potential difference.
Well, sort of, but trying to explain it w/o using the terms is hard. Neutral bonds to earth. So voltage (potential) difference is squat. If you measure neutral to ground, you get squat. If you measure hot to the same hot leg, you get squat. There is no DIFFERENCE. If you measure in your box L1 to neutral, you get 120v. If you measure in your box L2 to neutral, you get 120v. If you measure L1 to L2, you get 240. Wait, what? Each leg is only 120v to neutral, but they are 240 when measuring the difference between them because they are in opposite 240v appliances also don't need a neutral (unless they use L1 to power a 120v internal widget), as in the case of a 240v heater. I've installed many. You have 3 wires to the heater: L1, L2, Ground. No neutral needed. But how is this? You are measuring differences, and there is a potential difference of 240v between L1 an L2, so you don't need another conductor to have a difference to. Clear as mud? |
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Posted: 5/20/2021 5:46:20 PM EDT
[#8]
If all connections are sound, there should be no more than one volt between Neutral and Ground. Anywhere, period. And there should be no current on the ground. No switches in the neutral or ground.
Sorry I know it's just the simple answer. |
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Posted: 5/20/2021 5:47:59 PM EDT
[#9]
V=IR. Voltage between two points is the current times resistance. If the resistance is super low (as it should be in a wire) then voltage is very low, sometimes negligible, even with current.
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Posted: 5/20/2021 5:54:18 PM EDT
[#10]
Kind of related:
Our electrical power was acting weird (lights getting bright then dim all over the house) and I checked the voltage from the hot side to the neutral side at several receptacles. It was going up to about 130 volts and then down to about 110 volts, then back up, randomly. I called the power company. Squirrels had chewed the bare overhead neutral power line in two between the pole-mounted transformer and my electric meter at my house. The normal 120-volt power that feeds appliances and lights was having to find it's way from my breaker panel, down to my house's ground rod, then through the dirt to the ground rod at the power pole and then up to the transformer to close the circuit. The repair guy said that they see it all the time. There is a reason for that neutral conductor wire from your house to the transformer. Dirt is not nearly as good a conductor as metal wire, but it will do in a pinch. |
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Posted: 5/20/2021 5:59:07 PM EDT
[#11]
Quote HistoryQuoted: If all connections are sound, there should be no more than one volt between Neutral and Ground. Anywhere, period. And there should be no current on the ground. No switches in the neutral or ground. Sorry I know it's just the simple answer. A long extension cord and a power tool may cause the neutral measured at the end of the extension cord to be higher than 1V. |
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Posted: 5/20/2021 6:04:32 PM EDT
[#12]
Quoted: Is there voltage on a neutral conductor on a split phase residential system. 240v I’m not asking for the simple voltage difference bull shit answer. No shit there is no voltage differential from ground and neutral when measured on a meter. I’m talking about true alternating current “sine wave” pressure voltage. Ohms law says there has to be voltage if a conductor is carrying current. We damn well know neutral carries current. From an alternating current standpoint my mind says it has to....it’s alternating... From a sine wave center tap transformer stand point....maybe you are missing that half of the sine...but wouldn’t that mean 120v would be DC...and we know that’s not true. Someone clarify this for me please. I find most electricians only have the simple answer. Yes... ETA: Nevermind... |
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Posted: 5/20/2021 6:06:20 PM EDT
[#13]
Sounds like you are measuring from ground to 'ground' (ground and neutral are connected at the box.)
Under load there may be up to 2V, higher may indicate a problem. (fluke.com) |
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Posted: 5/20/2021 6:09:23 PM EDT
[#14]
Still getting the differential answer as it’s the way we measure it. I did not ask what the voltage differential from ground and neutral is.
Voltage is “pressure” to drive current. Neutral is a path back to the transformer is another thing I keep hearing that makes no sense. Its alternating current not direct. That makes zero sense. If the voltage and current changes direction 120 times a second from -170volts (or so for 240v split) to +170volts. How the hell is neutral not carrying the exact same voltage as line? That’s where I get lost. If you don’t agree that peak voltage is 160-170volts you may not want to chime in. Another that confuses me... if a circuit has a light bulb that draws 10 amps (big light bulb). If we measure current, which we can do. Neutral and line will both measure 10amps...ohms law saws? I’m not in question of what we can and can not measure. I’m questioning what’s really there that we can not. Maybe it can be measured with a scope? |
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Posted: 5/20/2021 6:14:22 PM EDT
[#15]
You understand ohms law incorrectly, it’s Va - Vb = IR. Delta V, the potential difference between two points.
You can swing from a high tension line and no current flows through you, but if you touched the ground while holding a high tension line you would die. Because there is a deltaV, Vline - Vground. |
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Posted: 5/20/2021 6:19:30 PM EDT
[#16]
Quote HistoryQuoted: Clear as mud? Very good explanation.  Ever an old master chief electrician understood it.  |
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Posted: 5/20/2021 6:33:07 PM EDT
[#17]
Quote HistoryQuoted: Still getting the differential answer as it’s the way we measure it. I did not ask what the voltage differential from ground and neutral is. Voltage is “pressure” to drive current. Neutral is a path back to the transformer is another thing I keep hearing that makes no sense. Its alternating current not direct. That makes zero sense. If the voltage and current changes direction 120 times a second from -170volts (or so for 240v split) to +170volts. How the hell is neutral not carrying the exact same voltage as line? That’s where I get lost. If you don’t agree that peak voltage is 160-170volts you may not want to chime in. Another that confuses me... if a circuit has a light bulb that draws 10 amps (big light bulb). If we measure current, which we can do. Neutral and line will both measure 10amps...ohms law saws? I’m not in question of what we can and can not measure. I’m questioning what’s really there that we can not. Maybe it can be measured with a scope? What’s the pressure at a single point? |
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Posted: 5/20/2021 6:34:56 PM EDT
[#18]
Quote HistoryQuoted: Still getting the differential answer as it’s the way we measure it. I did not ask what the voltage differential from ground and neutral is. Voltage is “pressure” to drive current. Neutral is a path back to the transformer is another thing I keep hearing that makes no sense. Its alternating current not direct. That makes zero sense. If the voltage and current changes direction 120 times a second from -170volts (or so for 240v split) to +170volts. How the hell is neutral not carrying the exact same voltage as line? That’s where I get lost. If you don’t agree that peak voltage is 160-170volts you may not want to chime in. Another that confuses me... if a circuit has a light bulb that draws 10 amps (big light bulb). If we measure current, which we can do. Neutral and line will both measure 10amps...ohms law saws? I’m not in question of what we can and can not measure. I’m questioning what’s really there that we can not. Maybe it can be measured with a scope? So the movement of electrons in an electric circuit is what does the work. Electrons repel each other, and want to spread out evenly across any conductive material. If electrons have trouble traveling in one direction or another due to resistance, they get more squished together reducing the voltage, or more spread apart, increasing the voltage. If you have a incandescent lightbulb, the filament has a fairly high resistance, which means that as electrons are pushed into and pulled out of the hot wire, only a small number of them are pushed across the filament to the neutral wire, and pulled back from the neutral wire, meaning the power plant pushing and pulling electrons can maintain the voltage "pressure". The number of electrons that cross the filament in the lightbulb is however many orders of magnitude more electrons than is needed to pressurize the hot wire to -170V and depressurize it to 170V (the capacitive load of the wire), so when looking at the current on the wire, the 10A is the measure of the number of electrons that are moving back and forth, and thus the number that cross the filament. On the neutral side those electrons that cross over the filament find a much more stable situation (although electrons are pulled back across the filament as well when the voltage on the hot side is high). There isn't a power plant pushing and pulling them around, rather there is a very large number of spikes into the ground, where they can find colossal numbers of friends to balance out with, like a huge pressure reservoir. Measuring the current on this side, even though the pressure is low, shows the same number of electrons (same amount of current) travelling to and from the neutral side of the lightbulb. But because of the stability of the ground connections, the neutral side does not have the same pressure as the power plant is putting onto the hot side. |
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Posted: 5/20/2021 6:41:14 PM EDT
[#19]
Quote HistoryQuoted: So the movement of electrons in an electric circuit is what does the work. Electrons repel each other, and want to spread out evenly across any conductive material. If electrons have trouble traveling in one direction or another due to resistance, they get more squished together reducing the voltage, or more spread apart, increasing the voltage. If you have a incandescent lightbulb, the filament has a fairly high resistance, which means that as electrons are pushed into and pulled out of the hot wire, only a small number of them are pushed across the filament to the neutral wire, and pulled back from the neutral wire, meaning the power plant pushing and pulling electrons can maintain the voltage "pressure". The number of electrons that cross the filament in the lightbulb is however many orders of magnitude more electrons than is needed to pressurize the hot wire to -170V and depressurize it to 170V (the capacitive load of the wire), so when looking at the current on the wire, the 10A is the measure of the number of electrons that are moving back and forth, and thus the number that cross the filament. On the neutral side those electrons that cross over the filament find a much more stable situation (although electrons are pulled back across the wire as well when the voltage on the hot side is high). There isn't a power plant pushing and pulling them around, rather there is a very large number of spikes into the ground, where they can find colossal numbers of friends to balance out with. Measuring the current on this side, even though the pressure it slow, shows the same number of electrons (same amount of current) travelling to and from the neutral side of the lightbulb. But because of the stability of the ground connections, the neutral side does not have the same pressure as the power plant is putting onto the line. I may have to read this ten times but may help my mind wrap around it. So you are saying the alternating push/pressure from the power company is only on L1 and L2 in this instance? It is not relative to the center tap. It’s more like a seesaw and neutral is the center pivot. On another note maybe my assumption of voltage is lacking or basic. Maybe the basic definition of comparing voltage to water pressure is not allowing me to think about the situation properly. |
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Posted: 5/20/2021 6:41:51 PM EDT
[#20]
No single line carries voltage on its own. You need both an inbound and outbound path for electricity to flow. Likewise, you need two points of contact to generate voltage. Neutral to ground should be near zero, as others have stated, neutral and ground are physically connected at the panel. You can't think of electricity like a hot spot. It's not a single point where you touch something, you get zapped. You need to think of it like a water line. Electrons flowing through a circuit are what create energy. If you cut off one line(and cap it), then no water flows no matter how much pressure you stack up on it.
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Posted: 5/20/2021 6:50:13 PM EDT
[#21]
Quote HistoryQuoted: I may have to read this ten times but may help my mind wrap around it. So you are saying the alternating push/pressure from the power company is only on L1 and L2 in this instance? On another note maybe my assumption of voltage is lacking or basic. Maybe the basic definition of comparing voltage to water pressure is not allowing me to think about the situation properly. Yes, the electric company usually distributes 3 phases of power, but houses are only wired with 2, and 120V circuits only use one of those 2. The neutral is basically a huge capacitor charged to 0V that you can run any one of the 3 phases produced by the electric company off of independently. It's a bit more complex than that in reality, but the electric company may or may not even use the neutral line directly in the generators. Edit: correction that 3 phase generators can use the neutral line, but whether that is through earth return or direct wire it will have a large connection to the same 0V virtually infinite electron source and sink that your house is connected to. It may be a lower resistance path to use the electric companies neutral line, but with the number of earth ground connections that wire is connected to across the electric grid, it's anyone's guess where your electrons are coming or going to, or where any electrons the power company is using are coming or going to. |
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Posted: 5/20/2021 6:51:28 PM EDT
[#22]
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Posted: 5/20/2021 7:00:11 PM EDT
[#23]
Resi 240v CT has the CT jammed into the earth (zero point). Each end to earth (zero) is 120v all the same phase. A resi 240v CT is one phase of a typical 3ph feeder.
If you lifted the neutral off of the GND wire in the panel, then touching the neutral to ground might bite you with 120vac(rms), and amps through you would vary depending on the resistance of the return path back to the source. As for current meaning voltage, yes, but see, the lines that carry the amps have relatively low ohms, and with some current you do have a small volt diff from the N point on the load to the N point in the panel. The load uses up the potential energy of the electrons (eV), the electrons lose their energy in the load and the electrons keep going back home. Does that explain it for you OP? Some might find this odd too, the xfrmer never really has 240v, a 240 CT 1ph has ±120v at the ends, which flip-flops 60Hz in US, 50Hz in other countries/places. The diff at the ends is 240v and each end to the CT is 120vac(rms). |
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Posted: 5/20/2021 7:08:21 PM EDT
[#24]
Quote HistoryQuoted: ... Maybe the basic definition of comparing voltage to water pressure is not allowing me to think about the situation properly. Think of neutral as a pipe to open air, and the hot wire as a pipe with alternating pressure and vacuum. If you have a high resistance passage between the hot side and the neutral, air will move between them, but because it's slow, compared with the small diameter hot and neutral pipes, it won't change the pressure on the neutral pipe which can quickly balance with the open air. The big problem with the analogy is that a lot of air is needed to make a sbustantial pressure difference in a pipe (the pipe analogy has tremendous capacitive load just in pressurizing and depressurizing the pipe) there is a lot of air moving back and forth just to make the pressure. In wires, very few electrons have to move to generate a large voltage. So alternating a wire between -170V and 170V, or even -1,000,000V and 1,000,000V takes a relatively small number of electrons for that "pressure", so there is very little capacitive load in wires. Although with million volt transmission systems, it is not insignificant like it is for 120V systems. |
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Posted: 5/20/2021 7:17:36 PM EDT
[#25]
Quote HistoryQuoted: Still getting the differential answer as it’s the way we measure it. Maybe I'm not understanding your question...but you seem to be asking for a definition of voltage that excludes the definition of voltage. Electrons like to flow from regions of high concentration to regions of low concentration. That difference in concentration is the voltage. It's convention to pick some part of the circuit and declare it to be the reference point, or 0V, and that's usually neutral/ground. Just because it's 0V doesn't mean it doesn't carry current. 0V is just an arbitrary reference point in the circuit and all other things are compared to it. Instead of 0V with +-120V legs, you could also do +380V on the neutral and 500V/260V legs, and the system would behave identically. It's just a matter of convention. There is no absolute voltage...only a difference between two points. |
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Posted: 5/20/2021 7:31:09 PM EDT
[#26]
I think where you are getting confused is not taking the load into account of the equation and how a load affects voltage.
Yes, the neutral carries current and if you broke the connection of a neutral and a load was connected, you would be able to measure the voltage on it but the load would not be able to work. |
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Posted: 5/20/2021 7:32:04 PM EDT
[#27]
Quote HistoryQuoted: Yes, the electric company usually distributes 3 phases of power, but houses are only wired with 2, and 120V circuits only use one of those 2. The neutral is basically a huge capacitor charged to 0V that you can run any one of the 3 phases produced by the electric company off of independently. It's a bit more complex than that in reality, but the electric company may or may not even use the neutral line directly in the generators. Edit: correction that 3 phase generators can use the neutral line, but whether that is through earth return or direct wire it will have a large connection to the same 0V virtually infinite electron source and sink that your house is connected to. It may be a lower resistance path to use the electric companies neutral line, but with the number of earth ground connections that wire is connected to across the electric grid, it's anyone's guess where your electrons are coming or going to, or where any electrons the power company is using are coming or going to. A resi single family dwelling is 1ph, not 2. A neighborhood will have a 3ph feeder nearby, and then those 3ph's are divided up among the homes, blocks using ph1, other blocks using ph2, and some more blocks using ph3. A 240CT xfrmer has only one (1) magnetic field in it, hence it's only a 1ph xfrmer. |
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Posted: 5/20/2021 7:37:24 PM EDT
[#28]
Quote HistoryQuoted: A resi single family dwelling is 1ph, not 2. A neighborhood will have a 3ph feeder nearby, and then those 3ph's are divided up among the homes, blocks using ph1, other blocks using ph2, and some more blocks using ph3. A 240CT xfrmer has only one (1) magnetic field in it, hence it's only a 1ph xfrmer. Quote HistoryQuoted: Quoted: Yes, the electric company usually distributes 3 phases of power, but houses are only wired with 2, and 120V circuits only use one of those 2. The neutral is basically a huge capacitor charged to 0V that you can run any one of the 3 phases produced by the electric company off of independently. It's a bit more complex than that in reality, but the electric company may or may not even use the neutral line directly in the generators. Edit: correction that 3 phase generators can use the neutral line, but whether that is through earth return or direct wire it will have a large connection to the same 0V virtually infinite electron source and sink that your house is connected to. It may be a lower resistance path to use the electric companies neutral line, but with the number of earth ground connections that wire is connected to across the electric grid, it's anyone's guess where your electrons are coming or going to, or where any electrons the power company is using are coming or going to. A resi single family dwelling is 1ph, not 2. A neighborhood will have a 3ph feeder nearby, and then those 3ph's are divided up among the homes, blocks using ph1, other blocks using ph2, and some more blocks using ph3. A 240CT xfrmer has only one (1) magnetic field in it, hence it's only a 1ph xfrmer. Ah okay. I see yeah. I always thought it was strange that it was called 240V with (what I thought was) only 120 degrees phase difference, that makes a lot more sense now. Thanks. |
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Posted: 5/20/2021 7:41:44 PM EDT
[#29]
Quote HistoryQuoted: Maybe I'm not understanding your question...but you seem to be asking for a definition of voltage that excludes the definition of voltage. Electrons like to flow from regions of high concentration to regions of low concentration. That difference in concentration is the voltage. It's convention to pick some part of the circuit and declare it to be the reference point, or 0V, and that's usually neutral/ground. Just because it's 0V doesn't mean it doesn't carry current. 0V is just an arbitrary reference point in the circuit and all other things are compared to it. Instead of 0V with +-120V legs, you could also do +380V on the neutral and 500V/260V legs, and the system would behave identically. It's just a matter of convention. There is no absolute voltage...only a difference between two points. Well, technically, there is absolute, because when you whittle it down, it's all about joules. A plate of charge, like in a capacitor, when you do work (expend energy) to push electrons to one side, 1J per 1C of electrons = 1v. In this example the cap holds potential energy in the electrons of 1J (1C x 1v). v=J/C. So technically there is absolute voltage, and you can read this using a V meter that has infinite ohms when you attach the probes. You only get amps when the differential is connected (ckt completed) so the electrons that have potential energy can rush-a-homa. |
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Posted: 5/20/2021 7:48:08 PM EDT
[#30]
Quote HistoryQuoted: I may have to read this ten times but may help my mind wrap around it. So you are saying the alternating push/pressure from the power company is only on L1 and L2 in this instance? It is not relative to the center tap. It’s more like a seesaw and neutral is the center pivot. On another note maybe my assumption of voltage is lacking or basic. Maybe the basic definition of comparing voltage to water pressure is not allowing me to think about the situation properly. Quote HistoryQuoted: Quoted: So the movement of electrons in an electric circuit is what does the work. Electrons repel each other, and want to spread out evenly across any conductive material. If electrons have trouble traveling in one direction or another due to resistance, they get more squished together reducing the voltage, or more spread apart, increasing the voltage. If you have a incandescent lightbulb, the filament has a fairly high resistance, which means that as electrons are pushed into and pulled out of the hot wire, only a small number of them are pushed across the filament to the neutral wire, and pulled back from the neutral wire, meaning the power plant pushing and pulling electrons can maintain the voltage "pressure". The number of electrons that cross the filament in the lightbulb is however many orders of magnitude more electrons than is needed to pressurize the hot wire to -170V and depressurize it to 170V (the capacitive load of the wire), so when looking at the current on the wire, the 10A is the measure of the number of electrons that are moving back and forth, and thus the number that cross the filament. On the neutral side those electrons that cross over the filament find a much more stable situation (although electrons are pulled back across the wire as well when the voltage on the hot side is high). There isn't a power plant pushing and pulling them around, rather there is a very large number of spikes into the ground, where they can find colossal numbers of friends to balance out with. Measuring the current on this side, even though the pressure it slow, shows the same number of electrons (same amount of current) travelling to and from the neutral side of the lightbulb. But because of the stability of the ground connections, the neutral side does not have the same pressure as the power plant is putting onto the line. I may have to read this ten times but may help my mind wrap around it. So you are saying the alternating push/pressure from the power company is only on L1 and L2 in this instance? It is not relative to the center tap. It’s more like a seesaw and neutral is the center pivot. On another note maybe my assumption of voltage is lacking or basic. Maybe the basic definition of comparing voltage to water pressure is not allowing me to think about the situation properly. Pressure, like water pressure in a hose, is read as the differential pressure between what is in the hose and atmospheric pressure on the outside of the hose. maybe that helps. |
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Posted: 5/20/2021 7:48:40 PM EDT
[#31]
Maybe OP has a "wild leg".
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Posted: 5/20/2021 7:50:41 PM EDT
[#32]
Not an EE.
Multi-wire residential branch circuits utilize 1 neutral for 2-120 volt circuits. 277/480 volt single phase circuits can use 1 neutral for 3 circuits. As I recall, current-wise it works due to the different phase angles of the power circuits. |
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Posted: 5/20/2021 7:57:13 PM EDT
[#33]
Quote HistoryQuoted: Ah okay. I see yeah. I always thought it was strange that it was called 240V with (what I thought was) only 120 degrees phase difference, that makes a lot more sense now. Thanks. This can be seen in areas where you see those cylindrical xrmers atop the pole, and three 7.2kv wires running pole to pole all around the neighborhood, and along the way the cylindrical 240CT xfrmer's will be attached to one of those three 7.2kv lines. Each 240ct will typically feed several homes in close proximity to the xfrmer. The poco will stagger the 240CT xfrmers to help create balance across their 3ph system. A single 3wire 3ph 240v delta delivers 240v only per phase (ph to ph, no CT for 120v). Using this xfrmer a poco can connect many homes in the neighborhood to a single xfrmer. Hi leg delta can give 120v/240v/208v, they add a CT to a coil in the delta. |
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Posted: 5/20/2021 8:04:25 PM EDT
[#34]
Quote HistoryQuoted: Not an EE. Multi-wire residential branch circuits utilize 1 neutral for 2-120 volt circuits. 277/480 volt single phase circuits can use 1 neutral for 3 circuits. As I recall, current-wise it works due to the different phase angles of the power circuits. You are talking about a multi wire branch ckt (MWBC), which is two breakers (a tied 2pole), one ckt on each pole, and they share one neutral wire. This is only a wiring method per the NEC codebook. Really has nothing to do with how many ckts a N could technically carry back to the panel. I could connect ten 15amp ckts and then use #14 from the loads tied back to say a #6 and then carry that back to the panel. This is not an allowed method by the NEC, MWBC is the only wire sharing method they allow. |
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Posted: 5/20/2021 8:14:24 PM EDT
[#35]
I think the OP is really meaning to ask does the Neutral wire carry current which, of course, yes it does.b
I think some of the confusion stems from the way that N is tied to ground. Most people generally understand what a ground fault is, and that it's undesirable, and so it doesn't seem right that N should carry current and appear to be a ground. The answer is that while the center tap of the transformer and the N of the panel are both connected to ground, in reality little to no current flows to ground, unless something has gone wrong, because the wire between the transformer and panel is a far lower resistance path for the current to follow. GFCI sockets work by measuring the difference between current flowing through the hot and neutral. Any difference means current must be flowing through the ground wires, which is potentially (ha!) dangerous. |
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Posted: 5/20/2021 8:18:23 PM EDT
[#36]
60hz
Which means a complete cycle every 0.016 seconds. Everything else has already been stated OP. The sine wave represents the shift between the neutral and hot as the cycle completes. Voltage measured as the potential between a source and ground, nothing else. So if the neutral doesn’t technically carry load, it can’t be a source can it? |
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Posted: 5/20/2021 8:35:29 PM EDT
[#37]
Quote HistoryQuoted: Still getting the differential answer as it's the way we measure it. I did not ask what the voltage differential from ground and neutral is. Voltage is "pressure" to drive current. Neutral is a path back to the transformer is another thing I keep hearing that makes no sense. Its alternating current not direct. That makes zero sense. If the voltage and current changes direction 120 times a second from -170volts (or so for 240v split) to +170volts. How the hell is neutral not carrying the exact same voltage as line? That's where I get lost. If you don't agree that peak voltage is 160-170volts you may not want to chime in. Another that confuses me... if a circuit has a light bulb that draws 10 amps (big light bulb). If we measure current, which we can do. Neutral and line will both measure 10amps...ohms law saws? I'm not in question of what we can and can not measure. I'm questioning what's really there that we can not. Maybe it can be measured with a scope? Measuring voltage isn't like measuring, say, temperature, or pounds, where you have an absolute unit w/ built in reference. It's more like measuring feet, it makes no sense unless you have two points to measure between. You won't have your voltage right behind every electron pushing it down the wire. Another thing amiss with the garden hose/pressure analogy BTW (I'm digressing a little): at some points in time, a garden hose can just be empty, just a hollow tube w/ no water inside. Turn the faucet on, and it takes a moment for water to transverse the hose and spray out the end. This is never true of a wire. The electrons are always already there in the copper wire itself, and rather than seeing an electron enter one end of the wire and expecting the same electron to emerge from the opposite end when the current flows, what you're really getting is more like a relay race, where the electrons already present in the copper atom's valance shells begin to displace one another; one new electron in, and old one pops out the other end, in chain fashio. Picture Newton's cradle, a good example of transfer of energy. |
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Posted: 5/20/2021 8:36:04 PM EDT
[#38]
Quote HistoryQuoted: You are talking about a multi wire branch ckt (MWBC), which is two breakers (a tied 2pole), one ckt on each pole, and they share one neutral wire. This is only a wiring method per the NEC codebook. Really has nothing to do with how many ckts a N could technically carry back to the panel. I could connect ten 15amp ckts and then use #14 from the loads tied back to say a #6 and then carry that back to the panel. This is not an allowed method by the NEC, MWBC is the only wire sharing method they allow. Quote HistoryQuoted: Quoted: Not an EE. Multi-wire residential branch circuits utilize 1 neutral for 2-120 volt circuits. 277/480 volt single phase circuits can use 1 neutral for 3 circuits. As I recall, current-wise it works due to the different phase angles of the power circuits. You are talking about a multi wire branch ckt (MWBC), which is two breakers (a tied 2pole), one ckt on each pole, and they share one neutral wire. This is only a wiring method per the NEC codebook. Really has nothing to do with how many ckts a N could technically carry back to the panel. I could connect ten 15amp ckts and then use #14 from the loads tied back to say a #6 and then carry that back to the panel. This is not an allowed method by the NEC, MWBC is the only wire sharing method they allow. That's true. I was hoping to further show how neutrals do carry current. |
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Posted: 5/20/2021 8:54:46 PM EDT
[#39]
Quote HistoryQuoted: I think you're taking the "pressure" analogy too far. It's not really a pressure in any physical sense, that's just the easiest analogy. Measuring voltage isn't like measuring, say, temperature, or pounds, where you have an absolute unit w/ built in reference. It's more like measuring feet, it makes no sense unless you have two points to measure between. You won't have your voltage right behind every electron pushing it down the wire. Another thing amiss with the garden hose/pressure analogy BTW (I'm digressing a little): at some points in time, a garden hose can just be empty, just a hollow tube w/ no water inside. Turn the faucet on, and it takes a moment for water to transverse the hose and spray out the end. This is never true of a wire. The electrons are always already there in the copper wire itself, and rather than seeing an electron enter one end of the wire and expecting the same electron to emerge from the opposite end when the current flows, what you're really getting is more like a relay race, where the electrons already present in the copper atom's valance shells begin to displace one another; one new electron in, and old one pops out the other end, in chain fashio. Picture Newton's cradle, a good example of transfer of energy. In general that's true for wires, although there are other ways of generating voltage differentials. A Van De Graff generator is a great example of that, where it has a non conductive belt to physically carry electrons from one conductor to another (and since the two conductors are insulated from each other, they can't find a way back). Very high voltages can be achieved, and it can be done safely enough you can buy a tabletop version for yourself that can generate 100,000 volts. The reason why is that while the voltages are high, that's only because of the substantial insulation between the conductors, and low capacitance. The small number of electrons needed to reach a 100,000 volt differential are not enough to do any significant work when released, even with the high voltage potential. Just enough to make a brief visible spark through the air. |
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Posted: 5/20/2021 8:57:19 PM EDT
[#40]
Quote HistoryQuoted: Voltage is a measurement of potential difference. Well, sort of, but trying to explain it w/o using the terms is hard. Neutral bonds to earth. So voltage (potential) difference is squat. If you measure neutral to ground, you get squat. If you measure hot to the same hot leg, you get squat. There is no DIFFERENCE. If you measure in your box L1 to neutral, you get 120v. If you measure in your box L2 to neutral, you get 120v. If you measure L1 to L2, you get 240. Wait, what? Each leg is only 120v to neutral, but they are 240 when measuring the difference between them because they are in opposite phase. L1 is -120v when L2 is +120v, etc. That is why you can power your entire panel with a 120v generator, just not run any 240v appliances. 240v appliances also don't need a neutral (unless they use L1 to power a 120v internal widget), as in the case of a 240v heater. I've installed many. You have 3 wires to the heater: L1, L2, Ground. No neutral needed. But how is this? You are measuring differences, and there is a potential difference of 240v between L1 an L2, so you don't need another conductor to have a difference to. Clear as mud? Opposite phase? So the power company brings in 2 phases? Neat! #learningnewthings |
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Posted: 5/20/2021 8:58:11 PM EDT
[#41]
Quote HistoryQuoted: Yes... ETA: Nevermind... Quote HistoryQuoted: Quoted: Is there voltage on a neutral conductor on a split phase residential system. 240v I’m not asking for the simple voltage difference bull shit answer. No shit there is no voltage differential from ground and neutral when measured on a meter. I’m talking about true alternating current “sine wave” pressure voltage. Ohms law says there has to be voltage if a conductor is carrying current. We damn well know neutral carries current. From an alternating current standpoint my mind says it has to....it’s alternating... From a sine wave center tap transformer stand point....maybe you are missing that half of the sine...but wouldn’t that mean 120v would be DC...and we know that’s not true. Someone clarify this for me please. I find most electricians only have the simple answer. Yes... ETA: Nevermind... I got a lot of amusement out of this post. 
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Posted: 5/20/2021 8:59:26 PM EDT
[#42]
Quote HistoryQuoted: Yes, the electric company usually distributes 3 phases of power, but houses are only wired with 2, and 120V circuits only use one of those 2. The neutral is basically a huge capacitor charged to 0V that you can run any one of the 3 phases produced by the electric company off of independently. It's a bit more complex than that in reality, but the electric company may or may not even use the neutral line directly in the generators. Edit: correction that 3 phase generators can use the neutral line, but whether that is through earth return or direct wire it will have a large connection to the same 0V virtually infinite electron source and sink that your house is connected to. It may be a lower resistance path to use the electric companies neutral line, but with the number of earth ground connections that wire is connected to across the electric grid, it's anyone's guess where your electrons are coming or going to, or where any electrons the power company is using are coming or going to. Quote HistoryQuoted: Quoted: I may have to read this ten times but may help my mind wrap around it. So you are saying the alternating push/pressure from the power company is only on L1 and L2 in this instance? On another note maybe my assumption of voltage is lacking or basic. Maybe the basic definition of comparing voltage to water pressure is not allowing me to think about the situation properly. Yes, the electric company usually distributes 3 phases of power, but houses are only wired with 2, and 120V circuits only use one of those 2. The neutral is basically a huge capacitor charged to 0V that you can run any one of the 3 phases produced by the electric company off of independently. It's a bit more complex than that in reality, but the electric company may or may not even use the neutral line directly in the generators. Edit: correction that 3 phase generators can use the neutral line, but whether that is through earth return or direct wire it will have a large connection to the same 0V virtually infinite electron source and sink that your house is connected to. It may be a lower resistance path to use the electric companies neutral line, but with the number of earth ground connections that wire is connected to across the electric grid, it's anyone's guess where your electrons are coming or going to, or where any electrons the power company is using are coming or going to. This is good stuff! Thanks! |
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Posted: 5/20/2021 8:59:30 PM EDT
[#43]
Quote HistoryQuoted: I think you're taking the "pressure" analogy too far. It's not really a pressure in any physical sense, that's just the easiest analogy. Measuring voltage isn't like measuring, say, temperature, or pounds, where you have an absolute unit w/ built in reference. It's more like measuring feet, it makes no sense unless you have two points to measure between. You won't have your voltage right behind every electron pushing it down the wire. Another thing amiss with the garden hose/pressure analogy BTW (I'm digressing a little): at some points in time, a garden hose can just be empty, just a hollow tube w/ no water inside. Turn the faucet on, and it takes a moment for water to transverse the hose and spray out the end. This is never true of a wire. The electrons are always already there in the copper wire itself, and rather than seeing an electron enter one end of the wire and expecting the same electron to emerge from the opposite end when the current flows, what you're really getting is more like a relay race, where the electrons already present in the copper atom's valance shells begin to displace one another; one new electron in, and old one pops out the other end, in chain fashio. Picture Newton's cradle, a good example of transfer of energy. I think he’s thinking an AC line acts like a DC line in terms of current flow. |
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Posted: 5/20/2021 8:59:58 PM EDT
[#44]
Quote HistoryQuoted: A resi single family dwelling is 1ph, not 2. A neighborhood will have a 3ph feeder nearby, and then those 3ph's are divided up among the homes, blocks using ph1, other blocks using ph2, and some more blocks using ph3. A 240CT xfrmer has only one (1) magnetic field in it, hence it's only a 1ph xfrmer. Quote HistoryQuoted: Quoted: Yes, the electric company usually distributes 3 phases of power, but houses are only wired with 2, and 120V circuits only use one of those 2. The neutral is basically a huge capacitor charged to 0V that you can run any one of the 3 phases produced by the electric company off of independently. It's a bit more complex than that in reality, but the electric company may or may not even use the neutral line directly in the generators. Edit: correction that 3 phase generators can use the neutral line, but whether that is through earth return or direct wire it will have a large connection to the same 0V virtually infinite electron source and sink that your house is connected to. It may be a lower resistance path to use the electric companies neutral line, but with the number of earth ground connections that wire is connected to across the electric grid, it's anyone's guess where your electrons are coming or going to, or where any electrons the power company is using are coming or going to. A resi single family dwelling is 1ph, not 2. A neighborhood will have a 3ph feeder nearby, and then those 3ph's are divided up among the homes, blocks using ph1, other blocks using ph2, and some more blocks using ph3. A 240CT xfrmer has only one (1) magnetic field in it, hence it's only a 1ph xfrmer. This sounds like #fakenews. |
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Posted: 5/20/2021 9:01:27 PM EDT
[#45]
Quote HistoryQuoted: A resi single family dwelling is 1ph, not 2. A neighborhood will have a 3ph feeder nearby, and then those 3ph's are divided up among the homes, blocks using ph1, other blocks using ph2, and some more blocks using ph3. A 240CT xfrmer has only one (1) magnetic field in it, hence it's only a 1ph xfrmer. Quote HistoryQuoted: Quoted: Yes, the electric company usually distributes 3 phases of power, but houses are only wired with 2, and 120V circuits only use one of those 2. The neutral is basically a huge capacitor charged to 0V that you can run any one of the 3 phases produced by the electric company off of independently. It's a bit more complex than that in reality, but the electric company may or may not even use the neutral line directly in the generators. Edit: correction that 3 phase generators can use the neutral line, but whether that is through earth return or direct wire it will have a large connection to the same 0V virtually infinite electron source and sink that your house is connected to. It may be a lower resistance path to use the electric companies neutral line, but with the number of earth ground connections that wire is connected to across the electric grid, it's anyone's guess where your electrons are coming or going to, or where any electrons the power company is using are coming or going to. A resi single family dwelling is 1ph, not 2. A neighborhood will have a 3ph feeder nearby, and then those 3ph's are divided up among the homes, blocks using ph1, other blocks using ph2, and some more blocks using ph3. A 240CT xfrmer has only one (1) magnetic field in it, hence it's only a 1ph xfrmer. The power co tries to balance the loads on the phases to minimize imbalances. But reality is unkind so voltage regulators make up the difference. |
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Posted: 5/20/2021 9:03:16 PM EDT
[#46]
Quote HistoryQuoted: In general that's true for wires, although there are other ways of generating voltage differentials. A Van De Graff generator is a great example of that, where it has a non conductive belt to physically carry electrons from one conductor to another (and since the two conductors are insulated from each other, they can't find a way back). Very high voltages can be achieved, and it can be done safely enough you can buy a tabletop version for yourself that can generate 100,000 volts. The reason why is that while the voltages are high, that's only because of the substantial insulation between the conductors, and low capacitance. The small number of electrons needed to reach a 100,000 volt differential are not enough to do any significant work when released, even with the high voltage potential. Just enough to make a brief visible spark through the air. Quote HistoryQuoted: Quoted: I think you're taking the "pressure" analogy too far. It's not really a pressure in any physical sense, that's just the easiest analogy. Measuring voltage isn't like measuring, say, temperature, or pounds, where you have an absolute unit w/ built in reference. It's more like measuring feet, it makes no sense unless you have two points to measure between. You won't have your voltage right behind every electron pushing it down the wire. Another thing amiss with the garden hose/pressure analogy BTW (I'm digressing a little): at some points in time, a garden hose can just be empty, just a hollow tube w/ no water inside. Turn the faucet on, and it takes a moment for water to transverse the hose and spray out the end. This is never true of a wire. The electrons are always already there in the copper wire itself, and rather than seeing an electron enter one end of the wire and expecting the same electron to emerge from the opposite end when the current flows, what you're really getting is more like a relay race, where the electrons already present in the copper atom's valance shells begin to displace one another; one new electron in, and old one pops out the other end, in chain fashio. Picture Newton's cradle, a good example of transfer of energy. In general that's true for wires, although there are other ways of generating voltage differentials. A Van De Graff generator is a great example of that, where it has a non conductive belt to physically carry electrons from one conductor to another (and since the two conductors are insulated from each other, they can't find a way back). Very high voltages can be achieved, and it can be done safely enough you can buy a tabletop version for yourself that can generate 100,000 volts. The reason why is that while the voltages are high, that's only because of the substantial insulation between the conductors, and low capacitance. The small number of electrons needed to reach a 100,000 volt differential are not enough to do any significant work when released, even with the high voltage potential. Just enough to make a brief visible spark through the air. What does a VDG have to do with AC power? |
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Posted: 5/20/2021 9:10:28 PM EDT
[#47]
Quote HistoryQuoted: What does a VDG have to do with AC power? Quote HistoryQuoted: Quoted: Quoted: I think you're taking the "pressure" analogy too far. It's not really a pressure in any physical sense, that's just the easiest analogy. Measuring voltage isn't like measuring, say, temperature, or pounds, where you have an absolute unit w/ built in reference. It's more like measuring feet, it makes no sense unless you have two points to measure between. You won't have your voltage right behind every electron pushing it down the wire. Another thing amiss with the garden hose/pressure analogy BTW (I'm digressing a little): at some points in time, a garden hose can just be empty, just a hollow tube w/ no water inside. Turn the faucet on, and it takes a moment for water to transverse the hose and spray out the end. This is never true of a wire. The electrons are always already there in the copper wire itself, and rather than seeing an electron enter one end of the wire and expecting the same electron to emerge from the opposite end when the current flows, what you're really getting is more like a relay race, where the electrons already present in the copper atom's valance shells begin to displace one another; one new electron in, and old one pops out the other end, in chain fashio. Picture Newton's cradle, a good example of transfer of energy. In general that's true for wires, although there are other ways of generating voltage differentials. A Van De Graff generator is a great example of that, where it has a non conductive belt to physically carry electrons from one conductor to another (and since the two conductors are insulated from each other, they can't find a way back). Very high voltages can be achieved, and it can be done safely enough you can buy a tabletop version for yourself that can generate 100,000 volts. The reason why is that while the voltages are high, that's only because of the substantial insulation between the conductors, and low capacitance. The small number of electrons needed to reach a 100,000 volt differential are not enough to do any significant work when released, even with the high voltage potential. Just enough to make a brief visible spark through the air. What does a VDG have to do with AC power? It's important because it does not take much work to alternate the voltage on the lines. Just like a Van De Graff generator can generate a very high voltage with few electrons, they can generate the high voltages on the lines quite easily without moving many electrons around. It's only when a load connects the hot line to the neutral (or to the other phase) line is any significant power needed. |
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Posted: 5/20/2021 9:19:11 PM EDT
[#48]
Quote HistoryQuoted: It's important because it does not take much work to alternate the voltage on the lines. Just like a Van De Graff generator can generate a very high voltage with few electrons, they can generate the high voltages on the lines quite easily. It's only when a load connects the hot line to the neutral (or to the other phase) line is any significant power needed. Quote HistoryQuoted: Quoted: Quoted: Quoted: I think you're taking the "pressure" analogy too far. It's not really a pressure in any physical sense, that's just the easiest analogy. Measuring voltage isn't like measuring, say, temperature, or pounds, where you have an absolute unit w/ built in reference. It's more like measuring feet, it makes no sense unless you have two points to measure between. You won't have your voltage right behind every electron pushing it down the wire. Another thing amiss with the garden hose/pressure analogy BTW (I'm digressing a little): at some points in time, a garden hose can just be empty, just a hollow tube w/ no water inside. Turn the faucet on, and it takes a moment for water to transverse the hose and spray out the end. This is never true of a wire. The electrons are always already there in the copper wire itself, and rather than seeing an electron enter one end of the wire and expecting the same electron to emerge from the opposite end when the current flows, what you're really getting is more like a relay race, where the electrons already present in the copper atom's valance shells begin to displace one another; one new electron in, and old one pops out the other end, in chain fashio. Picture Newton's cradle, a good example of transfer of energy. In general that's true for wires, although there are other ways of generating voltage differentials. A Van De Graff generator is a great example of that, where it has a non conductive belt to physically carry electrons from one conductor to another (and since the two conductors are insulated from each other, they can't find a way back). Very high voltages can be achieved, and it can be done safely enough you can buy a tabletop version for yourself that can generate 100,000 volts. The reason why is that while the voltages are high, that's only because of the substantial insulation between the conductors, and low capacitance. The small number of electrons needed to reach a 100,000 volt differential are not enough to do any significant work when released, even with the high voltage potential. Just enough to make a brief visible spark through the air. What does a VDG have to do with AC power? It's important because it does not take much work to alternate the voltage on the lines. Just like a Van De Graff generator can generate a very high voltage with few electrons, they can generate the high voltages on the lines quite easily. It's only when a load connects the hot line to the neutral (or to the other phase) line is any significant power needed. Huh. If it’s that easy to generate high voltage, why do power companies spend millions on generators and GSUs? |
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Posted: 5/20/2021 9:20:34 PM EDT
[#49]
Quote HistoryQuoted: V = IR I is the current of the devices using that neural as the return path, and R is the resistance to ground. R is very low so even with current, the voltage will be very low. PS: Unless you have some specialized system, your neutral line will be connected to earth ground just as the ground wire is, but the ground wire does not normally carry any current, so you may see the small voltage when comparing between neutral and ground, depending on the current being carried by the neutral line. An example, 12 AWG wire is 0.001588 ohms per foot. If you have 20A using that neutral, then that's around 0.03 volts per foot from the ground connection. Unless someone wired something whacky, and he gets a hold of the local earth ground lead and there's a potential on it. |
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Posted: 5/20/2021 9:21:15 PM EDT
[#50]
Quote HistoryQuoted: 60hz Which means a complete cycle every 0.016 seconds. Everything else has already been stated OP. The sine wave represents the shift between the neutral and hot as the cycle completes. Voltage measured as the potential between a source and ground, nothing else. So if the neutral doesn’t technically carry load, it can’t be a source can it? The word "ground" is often a confusing word, because the ends of the 240v xfrmer has no ground, just two ends that peak ±169.68v, thus your meter end to end read 240vac(rms). The CT is grounded, is the N and GND bonded in the panel, and is the N in the branch ckts. |
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