Pls explain hot, neutral, and ground in layman's terms

[JEDI]

ok, hot = black wire = 120V

What's the difference between neutral and ground since all neutral is wired together, and all ground is wired together.

And how does an electrician work on a live power outlet w/o electrocuting himself?

 

[akshatp]

Originally posted by: JEDI

And how does an electrician work on a live power outlet w/o electrocuting himself?

Only touch one live wire at a time.

 

[Special K]

I was under the impression that the current only traveled through the neutral wire, and the ground wire is only used to divert the current that would flow if something plugged into an outlet has a short circuit. But if the neutral and ground wires are in parallel, why wouldn't the current always flow through both of them?

 

[BillGates]

Originally posted by: akshatp

Originally posted by: JEDI

And how does an electrician work on a live power outlet w/o electrocuting himself?

Only touch one live wire at a time.

absolutely not true

 

[spidey07]

tagged.

I'm gonna run my EXTREMELY dumb opion, DO NOT TAKE THIS OPINTION AS FACT...

There are multiple leads you can have on power, most based on 3/4 wires. Power is delivered via the difference between hot and ground, neutral being the reference...

ah, screw it. I have no idea what I'm talking about. But you wouldn't believe the kinds of power used in data centers, that I can have an opinion on. The actual wiring and phase requirements...

 

[futuristicmonkey]

Neutral wire is only a method to divide the 240 volt service from your local transformer into two 120v lines. Some circuits may have only hot wires..google search '3 phase delta'. A ground wire is used as a low-impedance path for fault current; it serves two purposes. One, if the metal case of a refridgerator comes into contact with a live wire, the current will pass through the ground wire back to the source of electricity....not through you, if you were to touch the fridge and were grounded. Second, because it is (normally -- only talking residential stuff here) low impedance (resistance) it will allow enough current to flow to trip the circuit's breaker. The ground wire should never be used as a current-carrying wire. Never.

 

[iamwiz82]

Neutral completes the circuit. Think of them as one way streets. Hot is going out from the circuit breaker, and the neutral is the return. A ground is seperate from the system, and, obviously, grounds it. A neutral can be a ground, a ground can never be neutral

 

[Special K]

Originally posted by: futuristicmonkey
Neutral wire is only a method to divide the 240 volt service from your local transformer into two 120v lines. Some circuits may have only hot wires..google search '3 phase delta'. A ground wire is used as a low-impedance path for fault current; it serves two purposes. One, if the metal case of a refridgerator comes into contact with a live wire, the current will pass through the ground wire back to the source of electricity....not through you, if you were to touch the fridge and were grounded. Second, because it is (normally -- only talking residential stuff here) low impedance (resistance) it will allow enough current to flow to trip the circuit's breaker. The ground wire should never be used as a current-carrying wire. Never.

But if you try to measure the voltage between netural and ground you should measure 0, which implies they are in parallel, so why wouldn't some current flow through the ground path during normal operation?

 

[NoShangriLa]

Originally posted by: JEDI
ok, hot = black wire = 120V

What's the difference between neutral and ground since all neutral is wired together, and all ground is wired together.

And how does an electrician work on a live power outlet w/o electrocuting himself?

Neutral -- shielded -- complete circuit back to the breaker so that electrical device can operate.

Ground -- un-shield -- protect casing/user from shock hazard -- complete circuit back to breaker.

Old houses may use ground as neutral therefore it can be a fire/shock hazard.

Wirring can be work on in energize mode if the circuit is isolated.

240V uses two 110 hot lines to derive its voltage (old code 1 neutral, new code 2 neutrals).

 

[Analog]

Originally posted by: Special K

Originally posted by: futuristicmonkey
Neutral wire is only a method to divide the 240 volt service from your local transformer into two 120v lines. Some circuits may have only hot wires..google search '3 phase delta'. A ground wire is used as a low-impedance path for fault current; it serves two purposes. One, if the metal case of a refridgerator comes into contact with a live wire, the current will pass through the ground wire back to the source of electricity....not through you, if you were to touch the fridge and were grounded. Second, because it is (normally -- only talking residential stuff here) low impedance (resistance) it will allow enough current to flow to trip the circuit's breaker. The ground wire should never be used as a current-carrying wire. Never.

But if you try to measure the voltage between netural and ground you should measure 0, which implies they are in parallel, so why wouldn't some current flow through the ground path during normal operation?

Because the load is connected between hot and neutral. Ground is not connected to the load, just the chassis.

 

[Analog]

Also,

Ground fault circuitry measures the difference between the current flowing in the hot and neutral. Under normal circumstances, this current should be equal. If it is not, then some current is being diverted via ground (possibly thru a human), therefore the GFCI breaker will then disconnect the hot lead to prevent injury or death.

 

[CallMeJoe]

Originally posted by: Special K
But if you try to measure the voltage between neutral and ground you should measure 0, which implies they are in parallel, so why wouldn't some current flow through the ground path during normal operation?

Normally, there is no current flowing through the ground wire. Current flows exclusively between hot and neutral (in a standard 115 VAC circuit) because the ground wire is connected to neutral at the breaker/fuse box but not at the load. There is only current on the ground wire if the hot wire or some other part of the circuit shorts to the grounded case of the appliance. Current in the ground wire is used by Ground Fault Circuit Interrupter (GFCI) outlets to detect a short in the load, open the GFCI, and save your ass from frying.

edit: damn, Analog beat me to it.

 

[Special K]

Originally posted by: Analog

Originally posted by: Special K

Originally posted by: futuristicmonkey
Neutral wire is only a method to divide the 240 volt service from your local transformer into two 120v lines. Some circuits may have only hot wires..google search '3 phase delta'. A ground wire is used as a low-impedance path for fault current; it serves two purposes. One, if the metal case of a refridgerator comes into contact with a live wire, the current will pass through the ground wire back to the source of electricity....not through you, if you were to touch the fridge and were grounded. Second, because it is (normally -- only talking residential stuff here) low impedance (resistance) it will allow enough current to flow to trip the circuit's breaker. The ground wire should never be used as a current-carrying wire. Never.

But if you try to measure the voltage between netural and ground you should measure 0, which implies they are in parallel, so why wouldn't some current flow through the ground path during normal operation?

Because the load is connected between hot and neutral. Ground is not connected to the load, just the chassis.

But then I wouldn't necessarily always measure 0 V between the ground and neutral wires, correct?

 

[FlashG]

Moral of the story ?call a licensed electrician?

 

[edro]

Electricity tastes like... burning.

 

[iamwiz82]

Originally posted by: edro
Electricity tastes like... burning.

That's shocking...

 

[BrownTown]

Yes, in normal operation there should be 0V between them, but they are only connected at the breaker, not at the load, there is no path for curent to flow through the ground wire in normal operation.

 

[Special K]

When current flows through the ground wire, is it literally being diverted to the ground? Do buildings use their own frame and the surrounding earth as a conductor?

 

[Viperoni]

Originally posted by: Special K
When current flows through the ground wire, is it literally being diverted to the ground? Do buildings use their own frame and the surrounding earth as a conductor?

There's usually a copper pipe in the ground that is the ground. Incoming (cold) water pipes can be used as grounds.

 

[iRONic]

Originally posted by: JEDI
ok, hot = black wire = 120V
And how does an electrician work on a live power outlet w/o electrocuting himself?

Verrrry carefully.

 

[AlienCraft]

Originally posted by: Special K
When current flows through the ground wire, is it literally being diverted to the ground? Do buildings use their own frame and the surrounding earth as a conductor?

Yes, rebar embedded in the foundation is also used as a grounding element.

 

[JEDI]

Originally posted by: futuristicmonkey
Neutral wire is only a method to divide the 240 volt service from your local transformer into two 120v lines. Some circuits may have only hot wires..google search '3 phase delta'. A ground wire is used as a low-impedance path for fault current; it serves two purposes. One, if the metal case of a refridgerator comes into contact with a live wire, the current will pass through the ground wire back to the source of electricity....not through you, if you were to touch the fridge and were grounded. Second, because it is (normally -- only talking residential stuff here) low impedance (resistance) it will allow enough current to flow to trip the circuit's breaker. The ground wire should never be used as a current-carrying wire. Never.

so if i'm standing in a puddle of water and touch a 'live' fridge, nothing would happen because the fridge is grounded? or would something happen, and the breaker trips, thus saving my ass?

if so, how does the ground trip the breaker?

 

[AlienCraft]

Originally posted by: JEDI
ok, hot = black wire = 120V

What's the difference between neutral and ground since all neutral is wired together, and all ground is wired together.

And how does an electrician work on a live power outlet w/o electrocuting himself?

you must first realize that the neutral is the common winding of a transformer that has 240 v between the respective hot leads (secondary windings) . The case of the transformer and that common winding may be tied together but the main path to ground is at the panel board. (where the circuit breakers are)

the body has a relatively higher impedance and thus , in the event of a fault, follow that 'grounding conductor = green wire' to ground, away from the body.

An electrician is taking great care to only handle one wire at a time.

 

[AlienCraft]

Originally posted by: JEDI

Originally posted by: futuristicmonkey
Neutral wire is only a method to divide the 240 volt service from your local transformer into two 120v lines. Some circuits may have only hot wires..google search '3 phase delta'. A ground wire is used as a low-impedance path for fault current; it serves two purposes. One, if the metal case of a refridgerator comes into contact with a live wire, the current will pass through the ground wire back to the source of electricity....not through you, if you were to touch the fridge and were grounded. Second, because it is (normally -- only talking residential stuff here) low impedance (resistance) it will allow enough current to flow to trip the circuit's breaker. The ground wire should never be used as a current-carrying wire. Never.

so if i'm standing in a puddle of water and touch a 'live' fridge, nothing would happen because the fridge is grounded? or would something happen, and the breaker trips, thus saving my ass?

if so, how does the ground trip the breaker?

What you're describing is the action of ground fault interrupter. google how things work for a really great explanantion with pictures and stuff.

Appliances become "live" because of a fault developing , usually in the degrading insulation on motor windings., sometimes because of dust bunnies , grime, etc creating a conducting pathway. often cleaning solutions slosh from mops, etc can cause stuff to build up in places where it starts corrosion, which can attack parts, connections , insulation.
All of this can lead to arcing, leaking, etc.

A circuit breaker uses a bi metallic conductor and a magnet to hold the connection against a spring. that strip changes shape when heated.


Ground and neutral should be 0 v when measured, but switching power supplies generate third order harmonics and can induce eddy currents, which can cause voltages above the usual leakage voltages found in common systems.

 

[spidey07]

Originally posted by: AlienCraft

Originally posted by: Special K
When current flows through the ground wire, is it literally being diverted to the ground? Do buildings use their own frame and the surrounding earth as a conductor?

Yes, rebar embedded in the foundation is also used as a grounding element.

And in sensitive communications systems there is a common ground to with all communication cabling and active equipment is attached. Data centers have a real problem with grounding if you don't follow specs. You wouldn't believe how many problems are caused by improber grounding in data centers. It can reak havoc.