4 ms·

This blew my mind. So the white wire (neutral) is actually what I thought the ground was (connected to earth) and the “ground” wire (usually bare or green) is a

This blew my mind. So the white wire (neutral) is actually what I thought the ground was (connected to earth) and the “ground” wire (usually bare or green) is a conductor for clearing ground faults and isn’t connected to earth. Marvelous explanation.

vvillyd 7y ago
Thanks! In my 11 year experience in the electrical industry I have come to realize that there is a LOT of misinformation about how electrical systems work, and even the most experienced veterans in the field often don't really understand it.
- ryanmarsh 7y ago
  So what would be the potential consequence if I didn’t connect the “ground” wire (green or bare) to the little brass ground screw on (let’s say) a ceiling fan when installing it?
  - shreddish 7y ago
    From my understanding, if the hot wire (black) were to come in contact with a piece of metal on the fan it would build up electrical charge and or allow for current to pass through the piece of the fan. Then if you were on a ladder fixing the fan and touched that piece of metal you would become a path for electricity to pass through to a lower potential.
    - vvillyd 7y ago
      That's exactly correct. You would get shocked if you touched the fan.
      - chrisdhoover 7y ago
        The way you bond is codified too. The source feed is wire-nutted with a pigtail connected to the box, and to the ground of the device in parallel. If the bonding was daisy chained it could be interrupted when servicing or changing.
  - vvillyd 7y ago
    If you do not properly bond the ceiling fan (that is, connect the "ground" wire) then the circuit breaker will not trip if there is a fault to ground on the fan. That is, if the hot wire touches a metal part of the fan which is not supposed to be energized (say the metal housing), and the fan is not properly bonded, then there will be no ground-fault path back to the source to cause the breaker to trip. This could mean that the housing of your fan would be energized with (in a home in the US) 120V, and would shock anyone who touches it.
    - shreddish 7y ago
      Technically, would it only shock you if your body provided a path to "ground" or lower potential? For example if you were wearing insulted boots and touched the energized piece of metal you would not feel a shock, correct?
      - hyperman1 7y ago
        Please don't insult your boots.
        shreddish 7y ago
        hahah, they piss me off sometimes though
      - nosianu 7y ago
        Yes. That's why this is possible, here the insulation is the air between helicopter and ground: https://youtu.be/DPNK7bc2qvM?t=125 https://youtu.be/DPNK7bc2qvM?t=125 If that guy was connected to the earth he would get fried. Note that you still have to equalize whatever potential there is between you and the system, like they do in that video. Same reason why you should ground yourself and the hardware before working on your PC. Ever had a tiny spark hit you when you touched something (neither you or that "thing" being connected to the electrical grid, just static electricity e.g. from walking on the carpet)? But without connection to ground the only thing that happens is equalization of the potential between you and the target but no further flow. If you are connected to ground on one side and to a source that keeps creating an electrical potential, like the electrical grid with a power plant somewhere, there will be a continuing flow. If you are not connected to ground there won't be.
alexhutcheson 7y ago
They are both connected to earth at the same point. The big difference is that "neutral" has current flowing through it during normal operation, but "ground" only has current flowing through it in a fault condition.
- chrisdhoover 7y ago
  Right because the hot/black is connected to the neutral/white through the load completing a circuit so current flows. The “ground”/green is only connected to the chassis so no current flows in normal operation.
ars 7y ago
> conductor for clearing ground faults and isn’t connected to earth. > Marvelous explanation. It might be Marvelous, but it's not actually true. The ground wire IS connected to the earth! I don't want to be rude, but I think the OP should take this post down, it has a LOT of mistakes.
- jessaustin 7y ago
  TFA is a bit more abstract than you realize, and perhaps that abstraction could mislead the unwary. It is technically correct, but makes a distinction you've missed. If a gremlin cuts the (green) wire between my breaker box and my ground rod, the system is no longer "grounded to Earth", so it wouldn't handle lightning strikes well. However, the "EGC" in every house circuit is still bonded to neutral at the box, so breakers will still trip when the wire inside my clothes dryer rubs against the metal body. That is the function of the EGC. The EGC itself does nothing to protect against transient earth potentials like lightning strikes. That is the job of the grounding rod etc. Just because both wires are green, doesn't mean they're doing the same thing.
  - wrycoder 7y ago
    In the USA, there's no green wire between the service panel and the ground rod. The green wires end at the ground bus in the panel, which is bonded to the panel case. A heavy, bare copper wire leads from the ground bus to the ground rod. The neutral bus is either bonded to the case with a green grounding screw or is integral with the ground bus.

vvillyd 7y ago

Thanks! In my 11 year experience in the electrical industry I have come to realize that there is a LOT of misinformation about how electrical systems work, and even the most experienced veterans in the field often don't really understand it.

ryanmarsh 7y ago
So what would be the potential consequence if I didn’t connect the “ground” wire (green or bare) to the little brass ground screw on (let’s say) a ceiling fan when installing it?
- shreddish 7y ago
  From my understanding, if the hot wire (black) were to come in contact with a piece of metal on the fan it would build up electrical charge and or allow for current to pass through the piece of the fan. Then if you were on a ladder fixing the fan and touched that piece of metal you would become a path for electricity to pass through to a lower potential.
  - vvillyd 7y ago
    That's exactly correct. You would get shocked if you touched the fan.
    - chrisdhoover 7y ago
      The way you bond is codified too. The source feed is wire-nutted with a pigtail connected to the box, and to the ground of the device in parallel. If the bonding was daisy chained it could be interrupted when servicing or changing.
- vvillyd 7y ago
  If you do not properly bond the ceiling fan (that is, connect the "ground" wire) then the circuit breaker will not trip if there is a fault to ground on the fan. That is, if the hot wire touches a metal part of the fan which is not supposed to be energized (say the metal housing), and the fan is not properly bonded, then there will be no ground-fault path back to the source to cause the breaker to trip. This could mean that the housing of your fan would be energized with (in a home in the US) 120V, and would shock anyone who touches it.
  - shreddish 7y ago
    Technically, would it only shock you if your body provided a path to "ground" or lower potential? For example if you were wearing insulted boots and touched the energized piece of metal you would not feel a shock, correct?
    - hyperman1 7y ago
      Please don't insult your boots.
      - shreddish 7y ago
        hahah, they piss me off sometimes though
    - nosianu 7y ago
      Yes. That's why this is possible, here the insulation is the air between helicopter and ground: https://youtu.be/DPNK7bc2qvM?t=125 https://youtu.be/DPNK7bc2qvM?t=125 If that guy was connected to the earth he would get fried. Note that you still have to equalize whatever potential there is between you and the system, like they do in that video. Same reason why you should ground yourself and the hardware before working on your PC. Ever had a tiny spark hit you when you touched something (neither you or that "thing" being connected to the electrical grid, just static electricity e.g. from walking on the carpet)? But without connection to ground the only thing that happens is equalization of the potential between you and the target but no further flow. If you are connected to ground on one side and to a source that keeps creating an electrical potential, like the electrical grid with a power plant somewhere, there will be a continuing flow. If you are not connected to ground there won't be.

alexhutcheson 7y ago

They are both connected to earth at the same point. The big difference is that "neutral" has current flowing through it during normal operation, but "ground" only has current flowing through it in a fault condition.

chrisdhoover 7y ago
Right because the hot/black is connected to the neutral/white through the load completing a circuit so current flows. The “ground”/green is only connected to the chassis so no current flows in normal operation.

ars 7y ago

> conductor for clearing ground faults and isn’t connected to earth. > Marvelous explanation. It might be Marvelous, but it's not actually true. The ground wire IS connected to the earth! I don't want to be rude, but I think the OP should take this post down, it has a LOT of mistakes.

jessaustin 7y ago
TFA is a bit more abstract than you realize, and perhaps that abstraction could mislead the unwary. It is technically correct, but makes a distinction you've missed. If a gremlin cuts the (green) wire between my breaker box and my ground rod, the system is no longer "grounded to Earth", so it wouldn't handle lightning strikes well. However, the "EGC" in every house circuit is still bonded to neutral at the box, so breakers will still trip when the wire inside my clothes dryer rubs against the metal body. That is the function of the EGC. The EGC itself does nothing to protect against transient earth potentials like lightning strikes. That is the job of the grounding rod etc. Just because both wires are green, doesn't mean they're doing the same thing.
- wrycoder 7y ago
  In the USA, there's no green wire between the service panel and the ground rod. The green wires end at the ground bus in the panel, which is bonded to the panel case. A heavy, bare copper wire leads from the ground bus to the ground rod. The neutral bus is either bonded to the case with a green grounding screw or is integral with the ground bus.