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Regarding three-phase power: The electrical outlets in your home have two power-carrying prongs. The third prong is just for safety (it connects to the ground)

by s_tec 9y ago

Regarding three-phase power: The electrical outlets in your home have two power-carrying prongs. The third prong is just for safety (it connects to the ground), and should never carry power unless something is going horribly wrong. In that case, the power should hopefully prefer to reach the ground through that third wire than through your human body. Anyhow, the voltage in those two power-carrying wires is constantly switching directions. At one moment, the left wire will be +170 volts relative to the right wire, and then they will slowly switch places over the next 1/120 of a second so the right wire is at +170 volts. They continue trading places, completing a cycle every 1/60 of a second. At some point in this cycle, the voltage difference between the two wires will be zero, which means that no power will be flowing at that moment (power = voltage * current). On the average, the wires will deliver the same amount of power as-if they had a constant 120 volts between them, which is why people say that electricity in the USA runs at 120VAC. The peak-to-peak voltage is 170V, but the "RMS" average voltage is 1/√2 of that, or 120V. Anyhow, those brief moments of time where no power is flowing are a problem for a power company, who would like to deliver energy in a continuous stream. So, they build their power system with three wires. Each wire reaches its maximum voltage 1/180 of a second after the previous wire. Since the voltages on each wire are sine waves, when one wire is at 0, the other wires are at +√3/2 and -√3/2 of their maximum voltages. Therefore, there is no point where the power stops. In fact, due to a mathematical quirk, the power delivery is actually constant, even though the voltages on the three wires are constantly changing. Turing three-phase voltage into two phase voltage is pretty easy. Just pick any two of the three wires and hook them into the home. The difference of any two sine waves is just another sine wave at the same frequency, so you automatically have single-phase power. In practice, the power company will try to balance the load between the three pairs of wires by sending different pairs into different houses or even neighborhoods. Edit: As several people have pointed out, this isn't quite how it works in real life. See the comments below for details about the hot vs. neutral wire and how both 240V and 120V are available in the home at the same time.

wlesieutre 9y ago
Three phase power distribution is also more economical in terms of wiring. You need less conductor to distribute the same amount of power compared to running using two phase.
tripa 9y ago
This is the weirdest rationalization of three-phase power I've ever read. By your reasoning and disregarding cos phi issues, monophase power is also constant-zero power, since it's two wires anyway and one is always the opposite of the other. The best explanation of why three I was ever given hinged on "it's the number-of-phases argmin for the needed volume of wiring".
- ThrustVectoring 9y ago
  Three phase power is extraordinarily useful for electric motors. Mount three electromagnets radially and wire each up to a different phase, and you get a rotating magnetic field that spins on the axis. Electric generators produce three-phase power pretty naturally through the inverse process of spinning a magnet through the resistance provided by three groups of windings.
  - blattimwind 9y ago
    You can have a two phase power system[1], but two phase generators are less efficient and more expensive relative to three phase – for the exact same reason why power distribution is less efficient and more expensive relative to three phase. [1] two phases in quadrature, which is very different from split phase, which is not two phase at all.
    - ThrustVectoring 9y ago
      IIRC these designs don't naturally have torque at zero speed like three-phase induction motors do.
      - Animats 9y ago
        Yes. One of Tesla's more useful inventions was figuring out an simple way to get a synchronous motor started. Pre-Tesla schemes involved auxiliary starting motors and clutches. Tesla figured out how to run a synchronous motor in induction motor mode during starting.
trevyn 9y ago
Now: For two phase in your home, why is one side considered "hot" and the other side considered "neutral", resulting in keyed plug blades?
- wlesieutre 9y ago
  The two hot wires are perfectly out of phase, so connecting to both of them gives you 240V outlets (used for large appliances like clothes dryers). Your standard 120V appliance outlets are only using a single phase and neutral. IIRC the smaller prong is hot and the larger prong is neutral.
  - wlesieutre 9y ago
    Fun fact - the reason outlets in new construction are installed upside down (ground prong on top) is that the groudn prong can stop this from happening if something falls on it: https://i.redd.it/bm1gqw8hzppz.jpg https://i.redd.it/bm1gqw8hzppz.jpg Of course that's an ungrounded plug so they're in trouble either way, but you get the idea. Another option (which I've never seen in the US) is plugs where the first chunk of the line/neutral prongs are insulated: http://www.liddellappliancetesting.co.uk/ESW/Images/insulated-plug_5016.gif http://www.liddellappliancetesting.co.uk/ESW/Images/insulate...
    - oldcynic 9y ago
      UK has 240v for everything which may explain the insulation. Has been the standard about as long as I can remember - so back to the 70s. Someone put a lot of thought into the design. Ground at top to prevent accidents like you show. Ground pin is longer. Insulation covers enough of the pins that live and neutral disconnect before conductor is exposed from socket. Both will be fully disconnected before earth disconnects.
    - MertsA 9y ago
      It's not just new constructions, ground pin on the top has been the "correct" orientation for a long time. They've been installed "upside down" this whole time but that's what stuck. It's not in the NEC and while there was a suggestion to put the ground pin up, that has never been required by code and most people think that having the ground pin down looks correct. If you actually look at a NEMA 5 outlet with the ground pin compared to old ungrounded polarized NEMA 1 outlets the NEMA 5 outlet is rotated 180 degrees. The larger neutral slot is on the right on old outlets and with the ground pin down on a NEMA 5 outlet the neutral is on the left. It's not just for people dropping coins or paper clips on it though. Some outlet covers are metal and if the screw is loose or damaged that's basically guaranteed to short out if something is plugged in with the ground pin on the bottom. Another common thing is people using a tape measure along a wall, it's so thin that if there's a small gap it could shock someone using it or if you're lucky just short against the neutral.
kbenson 9y ago
I recently watched this youtube video[1] that explains three-phase power using water, and it was pretty useful and clear in explaining this to a layman like me. 1: https://www.youtube.com/watch?v=MnH_ifcRJq4 https://www.youtube.com/watch?v=MnH_ifcRJq4
dnm 9y ago
> the voltage in those two power-carrying wires is constantly switching directions I'm not buying this (in the USA). I've been in my breaker box. For a typical 110 volt outlet, the black (hot) wire is connected to the breaker, which is connected to one of the wires coming into the house from the street. The white (neutral) wire is connected to the same ground bracket that the bare (ground) wire is connected to. 240 volt connections (like my dryer and range) are taking a hot line from one of the lines coming into the house and another hot line from the other line coming into the house. You can see it on the bus bars in the breaker box. That's why dual breakers are used. Adjacent breakers pull for different bus bars. *edit typo
- twtw 9y ago
  The explanation in that paragraph is not necessarily incorrect, just confusing because it talks about voltage "in" wires and isn't clear about what two terminals are being referenced. It is true that the voltage between live and neutral changes sign, so neutral is sometimes 170V above live. But neutral is almost always at ground, and live goes to -170V relative to ground. That last paragraph though seems wrong, so OP may have been confused himself when writing.
- peteey 9y ago
  Ground is literally the ground. The Earth makes a good return path. The hot wire is going positive and negative relative to the land you stand on.
  - phasetransition 9y ago
    This isn't true in your home. The neutral is bonded to ground at a single point, in the main panel of your house. Current essentially all returns on the neutral to secondary of the pole xformer. The Earth is much higher impedance than the path back to the pole. Even during a ground fault event the current returns on the ground (technically EGC) to the bond point in the panel, and then from there back to the secondary of the utility pole. Grounding to earth itself mainly serves to hold the potential of your house near that of the pole.
- 9y ago
ars 9y ago
> The electrical outlets in your home have two power-carrying prongs. Only one of the prongs carries power. The other is attached to the earth, and is always at zero volts. > and then they will slowly switch places over the next 1/120 of a second so the right wire is at +170 volt No. The power prong (the smaller one) will switch from -170 to +170. The other one (the neutral) is always at zero (measured relative to you). > Turing three-phase voltage into two phase voltage is pretty easy. Just pick any two of the three wires and hook them into the home. This is not what they do. If they did they would not be able to have a neutral, and you would also not have an option of 240v. Homes don't have two phases, they have split phase. Instead they take a single phase, and attach it to a center tapped transformer, which I described here: https://news.ycombinator.com/item?id=16380133 https://news.ycombinator.com/item?id=16380133 > Just pick any two of the three wires and hook them into the home. In actuality the phases have 240 volts between them, not 120. And from any phase to neutral is 208 volts (which some devices make use of). (Those are voltages to customers. Internally they use other voltages - in particular when they use a single phase, power a street with it - they care about the voltage to neutral, not the voltage relative to another phase.)
- deleted 9y ago
  [deleted]
- aidenn0 9y ago
  While the second half of your comment is correct: >> The electrical outlets in your home have two power-carrying prongs. >Only one of the prongs carries power. The other is attached to the earth, and is always at zero volts. Voltages are about potential differentials, so "zero volts" is relatively meaningless without context. The neutral line is required by the electric code to be connected to earth at the electric panel, but even if it were not, any ungrounded appliances would work correctly. Both prongs absolutely carry power. Slap an ammeter on the neutral line; it should be identical to that on the hot line. Don't actually do this, but if you were to cut the neutral line with a live circuit, you would see sparks. This is particularly important when working on circuits with a shared neutral (two hot lines on alternate halves of the split phase with a single neutral line); despite the breaker being off for your hot line, you can get shocked when working on junction boxes for the neutral line. Yes this is up-to-code in all states (though a few places either recommend or require ganging the circuit breaker when doing so). >> and then they will slowly switch places over the next 1/120 of a second so the right wire is at +170 volt > No. The power prong (the smaller one) will switch from -170 to +170. The other one (the neutral) is always at zero (measured relative to you). Here you use voltages as a relative measure, which is correct. As a nitpick you do assume that the person is grounded. Walking on carpet in the winter, I can be at a potential of thousands of volts away from that though. [everything from here after in ars's comment is correct and I have no more nitpicks]
andmarios 9y ago
There aren't any mathematical tricks, rather how the real world (generator) translates to math. The generator at the power company has 3 stators that are on equal distance between each other on a circle. As the rotor rotates, it induces AC voltage at each of them. Because the rotor rotates at a stable speed, the AC voltage follows a sine function. Because the stators are placed 2/3pi apart, their sine waves have a phase difference of 2/3pi. Because 2/3pi+2/3pi+2/3pi=2pi, if you add them all together then you get 0 (sin[2pi]=0) and this is your neutral wire. Quite honestly I learned that very late in the university which is a pity. Once you see how the real world translates to math, many things (like euler's formula which is of utmost importance for engineers) fall in place.
- femto 9y ago
  Expanding on this: because the neutral current is close to zero, the conductor for the neutral current has looser requirements on its impedance. With perfectly balanced phases the neutral conductor can be eliminated, saving money and material. In practise, the Earth itself gets used as the neutral conductor. This is why one sees three wires in transmission lines and not four. Incidentally, the closely spaced multiple wires within each conductor of an electrical transmission line, typically held apart by spacers, act to reduce the inductance of the transmission line, which reduces losses. The little "dumbbells" which are on each side of each tower, are vibration dampers to reduce metal fatigue.
- phasetransition 9y ago
  Typical large generators will have between 12 and 24ph (in multiples of three). They're split out in triplets 120 degrees apart. If you see 12+ phases out in the wild, you're probably close to a power plant.
jsjohnst 9y ago
> As several people have pointed out, this isn't quite how it works in real life. “Isn’t quite how it works” is a gross understatement. I apologize, but while there’s some correct facts, the entire narrative you spun clearly shows you don’t have the first clue what you are talking about. I really want to be as polite as possible, but what did you expect to accomplish by posting this?
cameldrv 9y ago
This isn't correct for most residential installations in the U.S. for most of those, they have split phase power (https://en.wikipedia.org/wiki/Split-phase_electric_power https://en.wikipedia.org/wiki/Split-phase_electric_power) provided by a center tap transformer. This produces a neutral and two hot wires, each 180 deg out of phase from each other. Hook either hot to a neutral, and you get 120V, hook one hot to another and you get 240V. In some places though, (I know it's common in New York, and also in a lot of datacenters), they do something like you describe, and hook 2 phases of a 3 phase system together. Since these are only 120 deg out of phase from each other instead of 180 in the split-phase system, you get less voltage, specifically 208V.
logfromblammo 9y ago
To use an analogy of water in hoses, there are three tubes in a power circuit. There's a "hot" one, colored red or black. There's a "neutral" one, colored white. And there's a "ground" one, colored transparent or green. Under normal circumstances, the "hot" and "neutral" forms a continuous loop. But the pump that moves the water is connected to the "hot" hose. It alternates between pushing water out and sucking it back in. The "neutral" hose comes back from whatever is using the water and empties out into the tank that the pump uses as its water supply. As long as the loop stays intact, anything the pump pushes out to hot will come back around in the neutral and get dumped back into the tank. Anything the pump sucks out of the hot will come back around from the neutral and get sucked out of the tank. If you cut the neutral hose, the hot hose can still work, but only if you have a water reservoir at the other end big enough to accommodate a complete cycle of pushing and pulling. The pump operator doesn't like this too much, because it makes them reliant on customers to keep their water tanks in good condition, and if one gets damaged out there, the pump can't work as efficiently, and it could get damaged too. It's just safer for them to provide a second hose back to their own water tank. But if you cut the hot hose, breaking the loop, neutral's got nothing. The water in it just sits there. This is where the ground hose comes in. It is also shoved into the water tank at one end, same as neutral. It's sole purpose is to complete a loop back to the water tank in case the regular loop fails, so that water doesn't spray too far or let air get into the pump. Ground is the emergency backup return path. Connecting electrical wires to a ground rod pounded deep into the earth is like sticking the loose ends of your hoses in the ocean. You can pull as much water out of it as you need, and dump as much into it as you need. Sea level stays the same.

by s_tec 9y ago

wlesieutre 9y ago

Three phase power distribution is also more economical in terms of wiring. You need less conductor to distribute the same amount of power compared to running using two phase.

tripa 9y ago

This is the weirdest rationalization of three-phase power I've ever read. By your reasoning and disregarding cos phi issues, monophase power is also constant-zero power, since it's two wires anyway and one is always the opposite of the other. The best explanation of why three I was ever given hinged on "it's the number-of-phases argmin for the needed volume of wiring".

ThrustVectoring 9y ago
Three phase power is extraordinarily useful for electric motors. Mount three electromagnets radially and wire each up to a different phase, and you get a rotating magnetic field that spins on the axis. Electric generators produce three-phase power pretty naturally through the inverse process of spinning a magnet through the resistance provided by three groups of windings.
- blattimwind 9y ago
  You can have a two phase power system[1], but two phase generators are less efficient and more expensive relative to three phase – for the exact same reason why power distribution is less efficient and more expensive relative to three phase. [1] two phases in quadrature, which is very different from split phase, which is not two phase at all.
  - ThrustVectoring 9y ago
    IIRC these designs don't naturally have torque at zero speed like three-phase induction motors do.
    - Animats 9y ago
      Yes. One of Tesla's more useful inventions was figuring out an simple way to get a synchronous motor started. Pre-Tesla schemes involved auxiliary starting motors and clutches. Tesla figured out how to run a synchronous motor in induction motor mode during starting.

trevyn 9y ago

Now: For two phase in your home, why is one side considered "hot" and the other side considered "neutral", resulting in keyed plug blades?

wlesieutre 9y ago
The two hot wires are perfectly out of phase, so connecting to both of them gives you 240V outlets (used for large appliances like clothes dryers). Your standard 120V appliance outlets are only using a single phase and neutral. IIRC the smaller prong is hot and the larger prong is neutral.
- wlesieutre 9y ago
  Fun fact - the reason outlets in new construction are installed upside down (ground prong on top) is that the groudn prong can stop this from happening if something falls on it: https://i.redd.it/bm1gqw8hzppz.jpg https://i.redd.it/bm1gqw8hzppz.jpg Of course that's an ungrounded plug so they're in trouble either way, but you get the idea. Another option (which I've never seen in the US) is plugs where the first chunk of the line/neutral prongs are insulated: http://www.liddellappliancetesting.co.uk/ESW/Images/insulated-plug_5016.gif http://www.liddellappliancetesting.co.uk/ESW/Images/insulate...
  - oldcynic 9y ago
    UK has 240v for everything which may explain the insulation. Has been the standard about as long as I can remember - so back to the 70s. Someone put a lot of thought into the design. Ground at top to prevent accidents like you show. Ground pin is longer. Insulation covers enough of the pins that live and neutral disconnect before conductor is exposed from socket. Both will be fully disconnected before earth disconnects.
  - MertsA 9y ago
    It's not just new constructions, ground pin on the top has been the "correct" orientation for a long time. They've been installed "upside down" this whole time but that's what stuck. It's not in the NEC and while there was a suggestion to put the ground pin up, that has never been required by code and most people think that having the ground pin down looks correct. If you actually look at a NEMA 5 outlet with the ground pin compared to old ungrounded polarized NEMA 1 outlets the NEMA 5 outlet is rotated 180 degrees. The larger neutral slot is on the right on old outlets and with the ground pin down on a NEMA 5 outlet the neutral is on the left. It's not just for people dropping coins or paper clips on it though. Some outlet covers are metal and if the screw is loose or damaged that's basically guaranteed to short out if something is plugged in with the ground pin on the bottom. Another common thing is people using a tape measure along a wall, it's so thin that if there's a small gap it could shock someone using it or if you're lucky just short against the neutral.

kbenson 9y ago

I recently watched this youtube video[1] that explains three-phase power using water, and it was pretty useful and clear in explaining this to a layman like me. 1: https://www.youtube.com/watch?v=MnH_ifcRJq4 https://www.youtube.com/watch?v=MnH_ifcRJq4

dnm 9y ago

> the voltage in those two power-carrying wires is constantly switching directions I'm not buying this (in the USA). I've been in my breaker box. For a typical 110 volt outlet, the black (hot) wire is connected to the breaker, which is connected to one of the wires coming into the house from the street. The white (neutral) wire is connected to the same ground bracket that the bare (ground) wire is connected to. 240 volt connections (like my dryer and range) are taking a hot line from one of the lines coming into the house and another hot line from the other line coming into the house. You can see it on the bus bars in the breaker box. That's why dual breakers are used. Adjacent breakers pull for different bus bars. *edit typo

twtw 9y ago
The explanation in that paragraph is not necessarily incorrect, just confusing because it talks about voltage "in" wires and isn't clear about what two terminals are being referenced. It is true that the voltage between live and neutral changes sign, so neutral is sometimes 170V above live. But neutral is almost always at ground, and live goes to -170V relative to ground. That last paragraph though seems wrong, so OP may have been confused himself when writing.
peteey 9y ago
Ground is literally the ground. The Earth makes a good return path. The hot wire is going positive and negative relative to the land you stand on.
- phasetransition 9y ago
  This isn't true in your home. The neutral is bonded to ground at a single point, in the main panel of your house. Current essentially all returns on the neutral to secondary of the pole xformer. The Earth is much higher impedance than the path back to the pole. Even during a ground fault event the current returns on the ground (technically EGC) to the bond point in the panel, and then from there back to the secondary of the utility pole. Grounding to earth itself mainly serves to hold the potential of your house near that of the pole.
9y ago

ars 9y ago

> The electrical outlets in your home have two power-carrying prongs. Only one of the prongs carries power. The other is attached to the earth, and is always at zero volts. > and then they will slowly switch places over the next 1/120 of a second so the right wire is at +170 volt No. The power prong (the smaller one) will switch from -170 to +170. The other one (the neutral) is always at zero (measured relative to you). > Turing three-phase voltage into two phase voltage is pretty easy. Just pick any two of the three wires and hook them into the home. This is not what they do. If they did they would not be able to have a neutral, and you would also not have an option of 240v. Homes don't have two phases, they have split phase. Instead they take a single phase, and attach it to a center tapped transformer, which I described here: https://news.ycombinator.com/item?id=16380133 https://news.ycombinator.com/item?id=16380133 > Just pick any two of the three wires and hook them into the home. In actuality the phases have 240 volts between them, not 120. And from any phase to neutral is 208 volts (which some devices make use of). (Those are voltages to customers. Internally they use other voltages - in particular when they use a single phase, power a street with it - they care about the voltage to neutral, not the voltage relative to another phase.)

deleted 9y ago
[deleted]
aidenn0 9y ago
While the second half of your comment is correct: >> The electrical outlets in your home have two power-carrying prongs. >Only one of the prongs carries power. The other is attached to the earth, and is always at zero volts. Voltages are about potential differentials, so "zero volts" is relatively meaningless without context. The neutral line is required by the electric code to be connected to earth at the electric panel, but even if it were not, any ungrounded appliances would work correctly. Both prongs absolutely carry power. Slap an ammeter on the neutral line; it should be identical to that on the hot line. Don't actually do this, but if you were to cut the neutral line with a live circuit, you would see sparks. This is particularly important when working on circuits with a shared neutral (two hot lines on alternate halves of the split phase with a single neutral line); despite the breaker being off for your hot line, you can get shocked when working on junction boxes for the neutral line. Yes this is up-to-code in all states (though a few places either recommend or require ganging the circuit breaker when doing so). >> and then they will slowly switch places over the next 1/120 of a second so the right wire is at +170 volt > No. The power prong (the smaller one) will switch from -170 to +170. The other one (the neutral) is always at zero (measured relative to you). Here you use voltages as a relative measure, which is correct. As a nitpick you do assume that the person is grounded. Walking on carpet in the winter, I can be at a potential of thousands of volts away from that though. [everything from here after in ars's comment is correct and I have no more nitpicks]

andmarios 9y ago

There aren't any mathematical tricks, rather how the real world (generator) translates to math. The generator at the power company has 3 stators that are on equal distance between each other on a circle. As the rotor rotates, it induces AC voltage at each of them. Because the rotor rotates at a stable speed, the AC voltage follows a sine function. Because the stators are placed 2/3pi apart, their sine waves have a phase difference of 2/3pi. Because 2/3pi+2/3pi+2/3pi=2pi, if you add them all together then you get 0 (sin[2pi]=0) and this is your neutral wire. Quite honestly I learned that very late in the university which is a pity. Once you see how the real world translates to math, many things (like euler's formula which is of utmost importance for engineers) fall in place.

femto 9y ago
Expanding on this: because the neutral current is close to zero, the conductor for the neutral current has looser requirements on its impedance. With perfectly balanced phases the neutral conductor can be eliminated, saving money and material. In practise, the Earth itself gets used as the neutral conductor. This is why one sees three wires in transmission lines and not four. Incidentally, the closely spaced multiple wires within each conductor of an electrical transmission line, typically held apart by spacers, act to reduce the inductance of the transmission line, which reduces losses. The little "dumbbells" which are on each side of each tower, are vibration dampers to reduce metal fatigue.
phasetransition 9y ago
Typical large generators will have between 12 and 24ph (in multiples of three). They're split out in triplets 120 degrees apart. If you see 12+ phases out in the wild, you're probably close to a power plant.

jsjohnst 9y ago

> As several people have pointed out, this isn't quite how it works in real life. “Isn’t quite how it works” is a gross understatement. I apologize, but while there’s some correct facts, the entire narrative you spun clearly shows you don’t have the first clue what you are talking about. I really want to be as polite as possible, but what did you expect to accomplish by posting this?

cameldrv 9y ago

This isn't correct for most residential installations in the U.S. for most of those, they have split phase power (https://en.wikipedia.org/wiki/Split-phase_electric_power https://en.wikipedia.org/wiki/Split-phase_electric_power) provided by a center tap transformer. This produces a neutral and two hot wires, each 180 deg out of phase from each other. Hook either hot to a neutral, and you get 120V, hook one hot to another and you get 240V. In some places though, (I know it's common in New York, and also in a lot of datacenters), they do something like you describe, and hook 2 phases of a 3 phase system together. Since these are only 120 deg out of phase from each other instead of 180 in the split-phase system, you get less voltage, specifically 208V.

logfromblammo 9y ago

To use an analogy of water in hoses, there are three tubes in a power circuit. There's a "hot" one, colored red or black. There's a "neutral" one, colored white. And there's a "ground" one, colored transparent or green. Under normal circumstances, the "hot" and "neutral" forms a continuous loop. But the pump that moves the water is connected to the "hot" hose. It alternates between pushing water out and sucking it back in. The "neutral" hose comes back from whatever is using the water and empties out into the tank that the pump uses as its water supply. As long as the loop stays intact, anything the pump pushes out to hot will come back around in the neutral and get dumped back into the tank. Anything the pump sucks out of the hot will come back around from the neutral and get sucked out of the tank. If you cut the neutral hose, the hot hose can still work, but only if you have a water reservoir at the other end big enough to accommodate a complete cycle of pushing and pulling. The pump operator doesn't like this too much, because it makes them reliant on customers to keep their water tanks in good condition, and if one gets damaged out there, the pump can't work as efficiently, and it could get damaged too. It's just safer for them to provide a second hose back to their own water tank. But if you cut the hot hose, breaking the loop, neutral's got nothing. The water in it just sits there. This is where the ground hose comes in. It is also shoved into the water tank at one end, same as neutral. It's sole purpose is to complete a loop back to the water tank in case the regular loop fails, so that water doesn't spray too far or let air get into the pump. Ground is the emergency backup return path. Connecting electrical wires to a ground rod pounded deep into the earth is like sticking the loose ends of your hoses in the ocean. You can pull as much water out of it as you need, and dump as much into it as you need. Sea level stays the same.