Open Neutral

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kjroller

Senior Member
Location
Dawson Mn
Occupation
Master electrician
In an open neutral situation if there is no load will there be potential on ground? I believe no because it needs a load to flow back to source and without the resistance in the load it would be a dead short and breaker would trip. Let me know your thoughts.

Second question is in an open neutral situation with load like a fridge or microwave how does current actually find its way to back to source through ground since hot, neutral and ground are generally isolated from each other how does current actually find its way through the resistive load and back to ground or source when neutral is open that part puzzles me? (Ri is what confuses me in second question)equipment-connected-to-the-ground-neutral-wire-with-open-neutral.jpg
 
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kjroller said:
In an open neutral situation if there is no load will there be potential on ground? I believe no because it needs a load to flow back to source and without the resistance in the load it would be a dead short and breaker would trip. Let me know your thoughts.

Second question is in an open neutral situation with load like a fridge or microwave how does current actually find its way to ground since hot, neutral and ground are generally isolated from each other how does current actually find its way through the resistive load and back to ground or source when neutral is open that part puzzles me?
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In an open neutral situation of a 120V appliance, there would be no current flow anywhere. Current doesn't find its way to ground. What makes you think that it does?
 
Strathead said:
In an open neutral situation of a 120V appliance, there would be no current flow anywhere. Current doesn't find its way to ground. What makes you think that it does?
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If bonded at the panel the ground and neutral both go back to source if you turn on a lamp and it has an open neutral but the flow back to source is through the ground wire the lamp will still light up or flicker not well of course but in a sense, current would flow back to source through ground, would it not? If you cannot turn the appliance on, I understand but if the appliance is still running it found its way back to source and therefore would be drawing current on the ground, I have seen few, but some appliances or lights work but not efficiently with an open neutral.
 
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No. The bond in the service means that any electrons that make their way to the grounding conductor out in the field, which is a fault condition (ground fault or a neutral to ground connection which isn't legal) will then travel along the neutral back to the supplying transformer. Otherwise, the electron would need to travel through an alternate path, like the ground rod to the transformer ground rod, or a metal water pipe the the neighbor, backwards on their GEC to the water pipe, the through the neighbors neutral back to the panel. Or worse, you when you touch the shell of the lamp and you are grounded.

There is no path for an electron to jump from the hot or the neutral to the green conductor and then back to the panel. The only valid path is out the hot, and then back on the neutral or vice versa 60 times a second, since they can't go back the same way the went.
 
It is possible for an appliance to work with an open neutral if it flows back to the source through the ground. This occurs when the neutral wire is disconnected or loose, causing the current to flow through the ground wire instead of the neutral wire. This can lead to various issues, including flickering lights or malfunctioning appliances. It is crucial to address this issue promptly to prevent potential hazards such as electrical shock or fire. (I'm not saying this is safe, but this is how I understand it) The appliance should have enough resistance to not create a high enough amperage to then trip the breaker like in a true ground fault situation. I will try and find something that depicts what I'm saying better
 
Strathead said:
No. The bond in the service means that any electrons that make their way to the grounding conductor out in the field, which is a fault condition (ground fault or a neutral to ground connection which isn't legal) will then travel along the neutral back to the supplying transformer. Otherwise, the electron would need to travel through an alternate path, like the ground rod to the transformer ground rod, or a metal water pipe the the neighbor, backwards on their GEC to the water pipe, the through the neighbors neutral back to the panel. Or worse, you when you touch the shell of the lamp and you are grounded.

There is no path for an electron to jump from the hot or the neutral to the green conductor and then back to the panel. The only valid path is out the hot, and then back on the neutral or vice versa 60 times a second, since they can't go back the same way the went.
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Let's try this scenario then let's say the neutral comes off the appliance you're feeding and touches the case directly the appliance would find its way back to source would it not as long as its properly grounded and appliance would still run?
 
kjroller said:
Let's try this scenario then let's say the neutral comes off the appliance you're feeding and touches the case directly the appliance would find its way back to source would it not as long as its properly grounded and appliance would still run?
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That would actually be the same as old three wire range and dryer circuits.
 
Strathead said:
Perhaps if you draw out the circuit or find a sample on the site that depicts what you think you see we can help you better.
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roger said:
That would actually be the same as old three wire range and dryer circuits.
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I see my mistake now most of my experience with open Neutral was when it was touching the case of the metal box or enclosure energizing the enclosure in other words all of them. I was under impression that when the Neutral opened up current found its way to ground immediately. That is not the case that only happens when the neutral touches the case and we don't have a complete connection back to source through the panel in other words a 2-wire system or if the conduit was not completing path to earth. So, you don't have a good ground, and the neutral is touching the box.

If this description sounds better let me know
 
Strathead said:
In an open neutral situation of a 120V appliance, there would be no current flow anywhere. Current doesn't find its way to ground. What makes you think that it does?
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Every open neutral I have ever dealt with the metal box is hot that's where I get that from, but I am realizing that this is not the case correct?
 
kjroller said:
I see my mistake now most of my experience with open Neutral was when it was touching the case of the metal box or enclosure energizing the enclosure in other words all of them. I was under impression that when the Neutral opened up current found its way to ground immediately. That is not the case that only happens when the neutral touches the case and we don't have a complete connection back to source through the panel in other words a 2-wire system or if the conduit was not completing path to earth. So, you don't have a good ground, and the neutral is touching the box.

If this description sounds better let me know
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If the current was finding it's way back to the source via the EGC, you would have to have a fault. The current would/should never be on the EGC except in a fault. So, with an open neutral on 120V, you would have no current flow without there being a fault.
 
kjroller said:
Every open neutral I have ever dealt with the metal box is hot that's where I get that from, but I am realizing that this is not the case correct?
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When doing service work and measuring voltage I use one of those solenoid type voltage testers, a DMM can give you ghost readings. Also old metal boxes with no EGC or BX may misread on DMM.
That said I have occasionally run into energized boxes, one call to a small 1-bedroom apartment that had a 'shocking range', It ended up the utility neutral was burnt out, and for some reason at the panel everything buzzed out ok but from the range to a nearby ground I got around 60 volts, also there was a jbox for the range in the basement that was hot. Fixing the utility neutral fixed it inside.
 
kjroller said:
It is possible for an appliance to work with an open neutral if it flows back to the source through the ground. This occurs when the neutral wire is disconnected or loose, causing the current to flow through the ground wire instead of the neutral wire. This can lead to various issues, including flickering lights or malfunctioning appliances. It is crucial to address this issue promptly to prevent potential hazards such as electrical shock or fire. (I'm not saying this is safe, but this is how I understand it) The appliance should have enough resistance to not create a high enough amperage to then trip the breaker like in a true ground fault situation. I will try and find something that depicts what I'm saying better
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The only places where this was ever legal, which it isn't any more, is dryers and ranges. No other appliances that I am aware of ever allowed the ground to carry current. AND those appliances don't have a neutral.
 
Little Bill said:
If the current was finding it's way back to the source via the EGC, you would have to have a fault. The current would/should never be on the EGC except in a fault. So, with an open neutral on 120V, you would have no current flow without there being a fault
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I agree it would be a fault i agree not legal but as far as the theory goes if you have enough resistance and its not on a gfci torrent then the device would still work. Im not promoting it but shouldnt trip the breaker
 
In turn I have one last question lets say you lose the neutral at point of connection at 120 heater the wire is floating not touching any metal the case of that heater wont become energized correct ?
 
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Little Bill said:
If the current was finding it's way back to the source via the EGC, you would have to have a fault. The current would/should never be on the EGC except in a fault. So, with an open neutral on 120V, you would have no current flow without there being a fault.
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If open neutral downstream NG bond building disconect, and no another downstream NG bond, no shock hazard. But if open neutral upstream NG bond building disconect, there may shock hazard
 
Strathead said:
The only places where this was ever legal, which it isn't any more, is dryers and ranges. No other appliances that I am aware of ever allowed the ground to carry current. AND those appliances don't have a neutral.
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It was never legal for the ground (EGC) to carry current on stoves and dryers. It was the neutral that was allowed to also be the EGC. The ground was never allowed to be the neutral. I've seen 10-2 with bare ground hooked up to dryers but that was never legal/permitted.
 
Little Bill said:
It was never legal for the ground (EGC) to carry current .
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I am not doubting you but have always wondered where that code sections is? I want to cite it next time I run into those occupancy sensors that use the equipment ground to power the electronics.
I have actually seen a range converted to run on just '240' via a 6-50 welder plug, but all the elements were 240 the guy used a 50 watt control transformer to power the electronics so nothing ran on the equipment ground.
 
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