Amps on Neutral wire.

[shockingdave]

I am not certain if this is the right forum for this, but here is my question. I have a panel box with 240v total, 120 on each side of the bus. On one side I am reading 6 amps and on the other 8 amps, my question is this: "What is the acceptable amp load on the neutral?", I have always understood it to be zero, and this panel box is showing 4 on the neutral leg. I believe I may have a grounding issue or is there an acceptable level of amps on the neutral leg, without it resulting in a grounding issue.

 

[jumper]

Assuming a 120/240 single phase source, I believe that the neutral current should be the difference between the two ungrounded/hot conductors.

If you have 8 amps on A and 6 amps on B, I would have expected 2 amps on the neutral.

 

[roger]

The neutral carries the umballaced current, it would be a long shot to ever read zero amps on a neutral in a panel.

In a perfect world you should read 2 amps in your scenario considering this is a single phase panel

Roger

 

[shockingdave]

Thanks

Thanks

Thanks for information. I have questioned whether you could ever reach a zero on the neutral, but your answer now claries my questioning.

 

[Dennis Alwon]

Are all the loads in the panel 120V loads?

 

[kwired]

Are all the loads in the panel 120V loads?

Should still have 2 amps on the neutral. Question may be how accurate his meter is?

Otherwise neutral may be carrying current from a different source. Is there any current on the neutral when all loads are off? A bad neutral at the neighbors service and a good connection between the two places through a metal water pipe or any other path between the two, would make most/all of neighbors neutral current flow through your service neutral conductor.

 

[Dennis Alwon]

Is that true if you have a 240V load with a neutral connected to one phase as a range or dryer.

 

[david luchini]

Should still have 2 amps on the neutral. Question may be how accurate his meter is?

There is no way to predict 2 amps on the neutral, with the given information. The power factor of the loads isn't known.

If the loads were 6A at unity pf, and 8A at 0.90 pf, then the neutral would see 3.6A

 

[Rick Christopherson]

Those that are suggesting 4 amps indicates a problem are forgetting about powerfactor of the various loads. Currents with equal magnitudes but different phase angles will not fully cancel.

 

[gar]

110517-1359 EDT

The neutral could be anything between 0 and something towards 2 times one of the hots if both hots were equal in magnitude.

A vector sum of the individual currents in the neutral needs to be determined. Suppose one hot had a 10 A current leading by 90 deg, and the other had 10 A lagging by 90 deg. Since the two voltages are 180 deg apart that makes the two neutral currents in phase, and the neutral current is 20 A.

If you have only resistive loads, and equal supply voltages, then the magnitude of the neutral current is the absolute value of the difference of the two currents.

.

 

[iwire]

Continue discussion here.

[h=3]Unexplained neutral current[/h]