Sub panel neutral bar not testing isolated

[Stevenfyeager]

In this sub panel, the isolated or “floating” neutral bar tests continuous with the panel enclosure. Is this an error? Or do all isolated neutral bars test “bonded to panel” ?
Thank you

 

[charlie b]

I am aware of the concept of an "isolated ground," but not an "isolated neutral." On a subpanel, the neutral is not permitted to be bonded to the enclosure. So this sound like an error.

Did you intend to attach a photo of this subpanel?

 

[infinity]

In this sub panel, the isolated or “floating” neutral bar tests continuous with the panel enclosure. Is this an error? Or do all isolated neutral bars test “bonded to panel” ?

If the feeder EGC is connected to the sub-panel enclosure then the neutral (even if physically isolated from the enclosure) will show continuity between the two. That's because the neutral is bonded back at the service.

 

[Master Nater]

every neutral condctor should test continuous with every grounding electrode conductor. they meet at the system's neutral bonding point in the service disconnect. if they do not, the system is not correctly bonded. the only difference you should see, is that there should not be any amperage flow on the grounding electrode conductor (at least, VERY LITTLE). 99% of any unbalanced ampacity should be carried on the neutral conductor, not the EGC.

i say 99% and not 100%, because electricity takes EVERY path available back to it's source (utility source = transformer). the resistance of any grounding electrode path back to the transformer through the grounding electrode conductor (if possible) should be much higher than the resistance of the circuit through the neutral conductor, back to the transformer.

 

[winnie]

If the feeder EGC is connected to the sub-panel enclosure then the neutral (even if physically isolated from the enclosure) will show continuity between the two. That's because the neutral is bonded back at the service.

This^.

In a sub-panel, if the feeder neutral is disconnected, then the neutral bar should be isolated from ground.

But when the feeder neutral is connected, then there should be continuity just as @infinity says.

 

[infinity]

99% of any unbalanced ampacity should be carried on the neutral conductor, not the EGC

Under normal conditions no current should be on the EGC. Maybe you meant GEC which can carry a small amount of current. The OP is asking about the EGC (enclosure) and the neutral. This sub-panel may not even have a GEC.

 

[Master Nater]

Under normal conditions no current should be on the EGC. Maybe you meant GEC which can carry a small amount of current. The OP is asking about the EGC (enclosure) and the neutral. This sub-panel may not even have a GEC.

if that subpanel is in it's own structure, and requires it's own grounding electrode system, it would have the potential of having current flow. this all depends upon many factors, as you well know. i'm just saying, it's not 100% clear of having amperage flow. hence the 99%. (always, gotta have that disclaimer in there)

and that's not even getting into the possibility of reactance on non-cancelling fields in metallic raceways.

 

[ptonsparky]

A tester I used to use would show continuity with improperly bonded neutrals in sub panels or audible a 60hz hum with those that were not bonded. A slight voltage drop made the difference.

Good meters and knowing how to use them makes a difference.

 

[Stevenfyeager]

Thank you, I don't remember if I ever tested a floating neutral before.

 

[Stevenfyeager]

If the feeder EGC is connected to the sub-panel enclosure then the neutral (even if physically isolated from the enclosure) will show continuity between the two. That's because the neutral is bonded back at the service.

I was thinking about that, and also possibly I suppose in a switch box or outlet box, some ground may be touching a bare neutral wire or screw? (a regular outlet, that is. Because we know a gfi outlet would trip)

 

[infinity]

I was thinking about that, and also possibly I suppose in a switch box or outlet box, some ground may be touching a bare neutral wire or screw? (a regular outlet, that is. Because we know a gfi outlet would trip)

Continuity between the enclosure, EGC, and neutral is normal. It does not mean that there is a incorrect connection like in the box with a device that you've mentioned. The EGC is bonded to the neutral in the service disconnect enclosure or service panel by the MBJ so any continuity testing downstream of that connection will show a very low resistance (or continuity) between the two.

 

[roger]

The OP should draw it out all the way back to the service.

 

[ActionDave]

..... (a regular outlet, that is. Because we know a gfi outlet would trip)

Only if there is continuity from the neutral to the EGC.

 

[Little Bill]

I was thinking about that, and also possibly I suppose in a switch box or outlet box, some ground may be touching a bare neutral wire or screw? (a regular outlet, that is. Because we know a gfi outlet would trip)

Take everything loose from the subpanel, meaning all feeder conductors. You could also take the branch circuits loose if you think there may be a neutral touching an EGC somewhere. Then take your meter and check between the metal can and the neutral bar. There should be no continuity with everything disconnected.

 

[qcroanoke]

Continuity between the enclosure, EGC, and neutral is normal. It does not mean that there is a incorrect connection like in the box with a device that you've mentioned. The EGC is bonded to the neutral in the service disconnect enclosure or service panel by the MBJ so any continuity testing downstream of that connection will show a very low resistance (or continuity) between the two.

I would be concerned if there wasnt continuity
.

 

[herding_cats]

This^.

In a sub-panel, if the feeder neutral is disconnected, then the neutral bar should be isolated from ground.

But when the feeder neutral is connected, then there should be continuity just as @infinity says.

Exactly this is what I was going to comment but winnie said it clearly. The OP does not specify if the panel is wired or not.

 

[jaggedben]

I was thinking about that, and also possibly I suppose in a switch box or outlet box, some ground may be touching a bare neutral wire or screw? (a regular outlet, that is. Because we know a gfi outlet would trip)

Yes this is possible but in order to confirm it, where there's a properly bonded service, you need to turn off power and disconnect the neutral somewhere upstream.

We installed a brand of battery backup inverter that insisted there be no 'neutral loops' on backed up circuits. So before landing the backed up subpanel neutral, we would test it to the subpanel ground bar for continuity, hoping to find none. In one case we had continuity, so then we had to unland each branch circuit neutral and test for continuity on each of those to find the problem circuit. Of course the ground touching the neutral screw was on the very last receptacle we opened up on the identified branch circuit, because it was the receptacle behind the dresser.