Neutral and ground to same terminal in panelboard.

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Nickhxc4life

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Richmond, VA
So today I pulled my panel cover to add a new circuit breaker and found something fishy. There is an existing 15A/1P circuit breaker which goes to a junction box in my utility room. The breaker was off and labeled as spare. I flipped the breaker on and it shot out a spark and tripped right away. Upon closer investigation I noticed the ground and the neutral were both going to the same terminal hole/lug in the ground/neutral bar in the panel. Would this cause the breaker to trip without setting? Panel has only one bar for grounds and neutrals. No other circuits are attached to the bar like this (ground and neutral together). Panel is residential 120/240.

Thanks
 
Then the neutrals and EGC's are fine on the same bus. Should have nothing to do with your other short circuit or ground fault problem.
 
I’m not saying they just go to the same bus. I’m saying both the white neutral and the bare ground for that particular branch circuit are going to the exact same set screw. (2 wires 1 set screw)
 
I traced the wire which is exposed. No shorts or torn sheath. All wires in junction box are individually wire nutted. I thought neutral alternates current with the hot so wouldn’t this essentially cause a short to ground through the neutral?
 
Nickhxc4life said:
I traced the wire which is exposed. No shorts or torn sheath. All wires in junction box are individually wire nutted. I thought neutral alternates current with the hot so wouldn’t this essentially cause a short to ground through the neutral?
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This forum is for electricians and you obviously are not an electrician. You should call someone who is qualified to solve this problem. As has been stated, the neutral and ground on the same buss (even the same screw, which is electrically the same thing) is NOT your problem. Just because you don’t see the short IN the panel does not mean there is no short.
 
Nick, I'm in Richmond. I'll PM you my number.

Added: Don't worry, guys, I'll straighten him out. ;)
 
190602-2022 EDT

Nickhxc4life:

You need to study electrical circuit theory.

For your purposes the current in both a hot and its associated neutral are exactly the same in magnitude at any instant of time. If the hot and neutral are side by side, then the current in one is opposite in direction to the current in the other.

To troubleshoot your problem create a temporary receptacle at the main panel as follows. Remove the hot wire from the breaker, and connect this to the neutral terminal of the receptacle. Connect the breaker output to the receptacle hot terminal. Plug a 1500 W space heater into the receptacle. This puts the heater in series with the short. The heater will be somewhat above 10 ohms at 120 V, or about 10 A. This should not trip the breaker. When you find your problem and correct it, then the neutral terminal of this temporary receptacle will go to about 120 V.

Find a receptacle near the main panel, not on the problem circuit, and plug a long extension cord into this receptacle. This extension cord becomes a long test lead from the main panel to wherever you want to make measurements. At the end of the cord you have reference points from the main panel to compare with points in the troubled circuit.

Make measurements at various points in the troubled circuit, and see if you can figure out where your short is. If confused come back with values you measure.

In any event report back.

.
 
I’m an electrical engineer so I know enough. I typically deal in new work and three phase and and systems with separated neutral and ground bus. This is older residential so I asked a simple question. If you don’t have anything helpful to say then perhaps you shouldn’t have posted in the first place.

As as far as measuring there isn’t anything to measure. The wires go to a single junction box beside the panel and that’s it. I tested all the wires for continuity and everything checked out with no shorts. Hence why I asked about the neutral and ground as I thought someone may know something I didn’t already.
 
Nickhxc4life said:
I’m an electrical engineer so I know enough. I typically deal in new work and three phase and and systems with separated neutral and ground bus. This is older residential so I asked a simple question. If you don’t have anything helpful to say then perhaps you shouldn’t have posted in the first place.

As as far as measuring there isn’t anything to measure. The wires go to a single junction box beside the panel and that’s it. I tested all the wires for continuity and everything checked out with no shorts. Hence why I asked about the neutral and ground as I thought someone may know something I didn’t already.
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I hate to say this because you are an EE, but electrically, the "hot" wire has to have a short to ground for that breaker to flash and trip. If the wires are all connected together in the junction box (you didn't say) then you would expect what you experienced to happen.

But to your original question, no, the green and white wires terminated in the same hole will not cause what you experienced.
 
Yes the wire stubs out of the side of the panel and to a junction box on the same stud the panel is on. I removed the wire nuts and pulled the wire out of the box to test. Nothing abnormal. Everything I have read including reference to NEC says the neutral needs it’s own connection point which is why I asked the question. It mentions grouping EGCs If panel manufacturer allows but not a neutral and and EGC
 
The neutral must be in it's own hole in the neutral bar not shared with the EGC. Other than that electrically there is no problem.
 
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