neutral to ground voltage

[atatari]

Dear Friends,

I have an abnormal neutral to ground voltage...around 5 volts at the MCC.How can I find the problem?
what can cause this voltage?

Thanks for any feedback

 

[keithkyll]

The neutral and ground are tied to the same point in the distribution box. In your house, this would be the main breaker box.

A load on the neutral raises the line a couple of volts above ground. This is normal. It's caused by the resistance of the line, and the load on it. 5 volts might be a bit high, but not alarming. If the wiring isn't warm, then it's probably just a long run to the distribution point. If you need to lower it, run more neutrals, or increase the wire gauge.
The difference between ground and neutral is that ground never has a load. That way, it's always a true zero reference.

If you suspect a fault, there may be a corroded connection somewhere. Make measurements of neutral/ground voltage along several points tracing back to the box. The voltage will be lower the closer you get to the box. A big jump indicates a problem.

 

[atatari]

Thanks for the reply.

But I thought the unbalanced load or harmonics can lead to higher volatges on neutral.Yes,it's true that the neutral and ground are only supposed to be joint at the srvice entrance,however if in some other location in the plant these two are connected togetther,this can lead to current passing through ground.
Is this right?

 

[keithkyll]

Yes, but that's a serious problem. If you're drawing current on the ground lead, then you don't have a ground. You have 2 neutrals.

This is a violation. An inspector will shut you down. All safety is defeated in a situation like this.
Never draw current on Ground! Period.