Neutral Connection in a System Grounding

[bobby ocampo]

If the current is taking any unintended path it is a fault. Lets say that you have a 3-wire system with a conductor touching a metallic raceway.
If the system is bonded to the raceway, but not to ground. Any fault to the raceway will be sensed as an unintended current flow, ground (dirt) is not necessary.

How do you reduce hazard of electric shock in an UNGROUNDED AND HRG SYSTEM with a single line-to-ground energizing a metal piece of equipment?

If the 3-wire system is not bonded then there is no fault;the first connection to the raceway simply creates a bonding path.

Sir please clarify what you mean in this comment.

 

[jim dungar]

The best way to reduce electric shock in a very LOW FAULT CURRENT is to connect the metal piece to the ground.

No, the best way to reduce electrical shock (on max 600V systems) is to bond all of the possible current paths together. As I sit in my kitchen right now I see lots of metallic surfaces but nowhere do I see ground. What protects me from electrical shock is what the NEC calls an equipment grounding conductor(EGC) to each device not the physical connection of any part of the system to ground/dirt/earth. If it is important to include the reference plane in this system then I need to bond to my wooden kitchen floor not the dirt outside.

 

[bobby ocampo]

No, the best way to reduce electrical shock (on max 600V systems) is to bond all of the possible current paths together. As I sit in my kitchen right now I see lots of metallic surfaces but nowhere do I see ground. What protects me from electrical shock is what the NEC calls an equipment grounding conductor(EGC) to each device not the physical connection of any part of the system to ground/dirt/earth. If it is important to include the reference plane in this system then I need to bond to my wooden kitchen floor not the dirt outside.

Isn't it that the bonded EGC is connected to earth through a ground rod or other means acceptable in the CODE in the Service Equipment? Isn't this the reference plane you are discussing?

 

[ronaldrc]

You can say that your not talking about removing the solid ground, but it I see this discussion leading in that direction.


I remember a few years back on another Electrical forum we where talking about this very thing.

And one who is posting in this thread now agreed with me at that time that a high resistance grounding system or even a spark gap would be more safe than the solidly grounded system.

And I agree with that, as long as we keep our wiring for swimming pools and lighting Eq. and the like out of the ground. Because sooner or later something underground is going to fault and more and likely this is going to be line #1 or #2 and not the neutral. And as I have heard from most on here and is true we want have a glue that our system is now a grounded system and is grounded with a potential of 240 volts shock and fire hazard which will not trip the breaker.The way we have it now with the neutral already grounding we are know the next fault will be just a 120 fault instead of a 240 volt fault which is more and likely to cause a fire if it doesn't trip a breaker.

And the GFI receptacle. want work without a grounding electrode system. it doesn't have to an Equipment ground to the receptacle but the neutral has to be hooked to the earth somewhere on the system.

 

[LarryFine]

If the current is taking any unintended path it is a fault. Lets say that you have a 3-wire system with a conductor touching a metallic raceway.
If the system is bonded to the raceway, but not to ground. Any fault to the raceway will be sensed as an unintended current flow, ground (dirt) is not necessary. If the 3-wire system is not bonded then there is no fault;the first connection to the raceway simply creates a bonding path.

But a GFCI meant for personnel protection doesn't know or care what the second surface being contacted is. If a person is touching a bonded (to the system neutral) raceway and makes accidental contact with a hot wire, no earthing of the system is necessary for the GFCI device to operate.

However, if a person is touching a non-electrical conductive surface, such as a concrete floor, building steel, earth outdoors, etc., when the accidental touch of the hot wire occurs, a system-neutral-to-earth bond (aka a grounded system) is required for both the shock and the GFCI operation.

I would imagine that most shocks fall under the conditions of the second description above. With a grounded supply system, all bases are covered.

 

[LarryFine]

And one who is posting in this thread now agreed with me at that time that a high resistance grounding system or even a spark gap would be more safe than the solidly grounded system.

Agreed. An ungrounded system renders the GFCI device both unnecessary and non-functional.

And the GFI receptacle. want work without a grounding electrode system. it doesn't have to an Equipment ground to the receptacle but the neutral has to be hooked to the earth somewhere on the system.

Exactamundo! Without an earth ground connection, an accidental contact between a hot wire and earth will not generate enough current to trip the GFCI device.

The bad news is that the GFCI device won't trip. The good news is that the GFCI device won't need to. The great thing about GFCI devices is that they don't care how the hazardous current is flowing, just that it is.

 

[ronaldrc]

Larry
The good news is that the GFCI device won't need to.


But what about when that underground wiring faults and makes this a unknown grounded system?

It might be a life saver that.

 

[don_resqcapt19]

And the GFI receptacle. want work without a grounding electrode system. it doesn't have to an Equipment ground to the receptacle but the neutral has to be hooked to the earth somewhere on the system.

Why won't it work? If there is current flowing on some path other than the two circuit conductors, the device will trip. If current can't flow on any other path, then there is no shock hazard. As has been pointed out there is capacitance coupling to earth and current flowing via this path will open the device if the current exceeds 5mA.

 

[brian john]

1st The earth does not care about our electrical systems and in 600 VAC and under the earth connection plays a minor role in the safety of the end users. Lightning and accidental connection to the utility primary.

and the like out of the ground. Because sooner or later something underground is going to fault and more and likely this is going to be line #1 or #2 and not the neutral.

Actually neutral to ground faults are more common, as phase to ground faults hopefully operate a CB and are repaired, neutral to ground faults are generally unknown to the end user and therefore not repaired.

For this reason, the code requires a ground fault protection for OCPD of 1000 amps and more for system voltages of more than 150 volts to ground with a maximum setting of only 1200 amps. The current in this situation may not trip the circuit breaker without ground fault protection. If this ARCING GROUND FAULT happens inside the metal piece, it will increase the potential of the metal piece and if the EGC is not connected to the ground there is a big hazard of electric shock. If the metal piece is energized by the arcing ground fault and fault current is low enough not to trip the OCPD despite of the single line to ground fault then the only protection is the connection of the bonded EGC to earth.

EARTH has nothing to do with this............................................

I bet you big bucks I can set up a GFP system in space with no connection to earth and it will work AS LONG AS WE BOND all metallic components.

 

[ronaldrc]

As has been pointed out there is capacitance coupling to earth and current flowing via this path will open the device if the current exceeds 5mA.

Don, you know better than a lot of us this would never equal or be more than a few micro amps.

And the capacitance coupling would be felt more or less equally between the grounded and ungrounded conductors.

 

[ronaldrc]

Its to late to edit so I need to retract that statement about being equally felt by both conductors because your talking about being in direct contact with the hot wire.

But I still stand behind my comment that it would not trip the GFI recpt..

 

[don_resqcapt19]

Don, you know better than a lot of us this would never equal or be more than a few micro amps.

And the capacitance coupling would be felt more or less equally between the grounded and ungrounded conductors.

I have had my wiggy pick-up when checking phase to ground on ungrounded systems. At 120 volts the wiggy takes about 20mA to pick up. Now maybe there were ground faults on the ungrounded systems and that is why the wiggy picked up. I really don't know.

 

[LarryFine]

Why won't it work? If there is current flowing on some path other than the two circuit conductors, the device will trip.

That's my point. If the supply is ungrounded, that means no conductors are bonded to earth, metallic parts, etc. There's no real 'hot' wire relative to earth. Therefore, there's no "real" current path back to another condcutor of the supply through a person's body.

If current can't flow on any other path, then there is no shock hazard.

Right. That's what I meant by the GFCI being unnecessary. The GFCI is designed to protect when current in one condcutor is not returning to the supply in another, but instead through a persons body to the natural 'other' conductor, earth, which requires an earthe conductor.

It should be safe to presume that only an eletrician would be in a position to contact more than one circuit conductor at one moment. Likewise, a GFCI will not trip if someone, say, touches both prongs of a partially-inserted plug, unless they're also grounded (and the system is, too.)

 

[LarryFine]

I have had my wiggy pick-up when checking phase to ground on ungrounded systems. At 120 volts the wiggy takes about 20mA to pick up. Now maybe there were ground faults on the ungrounded systems and that is why the wiggy picked up. I really don't know.

That's the magic of a GFCI device: it will function by design when a dangerous (i.e. >5ma) current flows through an unintended path. It will function equally well on an intentionally-grounded system, or an unintentionally-grounded one. Just not on an ungrounded one.

If the wiggy is detecting 20ma of current to earth on a supposedly-ungrounded system, then the GFCI will function. By literal definition, this is not really an ungrounded system due to whatever leakage you're reading.

My wiggy's neon bulb reads voltages its solenoid doesn't react to. I would ask whether that reading is equal on all line conductors, and if it's capable of powering a real practical load. My guess is no.

 

[jim dungar]

Isn't it that the bonded EGC is connected to earth through a ground rod or other means acceptable in the CODE in the Service Equipment? Isn't this the reference plane you are discussing?

The NEC does require us to connect our electrical system to ground/dirt, but there is no engineering/physics based reason to do so for voltages less than 600V. Bonding all conductive surfaces together is the action that will reduce the chance of electric shock. In my kitchen standing on a wooden floor, my safety is not dependent upon the fact that my electrical service is connected to ground/dirt.

 

[ronaldrc]

Now maybe there were ground faults on the ungrounded systems and that is why the wiggy picked up. I really don't know.

I respect your honesty.

If the ungrounded system had line fault monitors on it which I'm sure it did
that would be enough for your wiggy to pick up on.

Larry I'm not sure about this but isn't the neon tester on a wiggy shunt by the selenoid coil?

 

[LarryFine]

Larry I'm not sure about this but isn't the neon tester on a wiggy shunt by the selenoid coil?

Yes, but so what? It doesn't take much to make at least one electrode glow in a neon bulb.

Remember, solenoids actually respond to current.

 

[ronaldrc]

Your probably right

I don't know how much it takes to light a neon they are very sensitive.

 

[bobby ocampo]

The NEC does require us to connect our electrical system to ground/dirt, but there is no engineering/physics based reason to do so for voltages less than 600V.

NEC requires it to be connected to ground for the reason that it will reduce the potential of an accidentally energized metal piece to ground potential and therefore reduce electric shock hazard. Otherwise NEC would have removed it a long time ago.

Proof of this is is in a single line-to-ground fault in an ungrounded system or HRG SYSTEM.

Bonding all conductive surfaces together is the action that will reduce the chance of electric shock. In my kitchen standing on a wooden floor, my safety is not dependent upon the fact that my electrical service is connected to ground/dirt.

Bonding without connection to the reference plane will still have a an electric shock hazard. This is the reason and the PHYSICS behind why NEC requires it to be connected to ground through a ground rod or other acceptable means in the NEC.

 

[peter d]

Bonding without connection to the reference plane will still have a an electric shock hazard. This is the reason and the PHYSICS behind why NEC requires it to be connected to ground through a ground rod or other acceptable means in the NEC.

So again I ask, how do we accomplish this all important connection to earth in a ship or an airplane? The structure of a ship or plane and EGC's are bonded to the source neutral and never connect to dirt.