Potentially Loose Neutral?

[Scottybars2288]

I have 800 amp services on the end of each building. each with 18 meters 1ph 120/208 125a-
one with an additional house meter, 3ph 4w 120/208 225. I noticed in the house panel and in the 125 amp 1ph panel, i’d have straight continuity between the neutral and ground, as I should. Once I turn on the lighting circuits the the continuity on my meters sounds like it comes and goes, like something is disrupting it or it’s loose. Comes back when lighting is turned off again. Continuity between neutral and ground at the service remains even while everything is energized, unlike the panel. my feeder connections are tight and neutral bonded in the main cabinet. From each service I have a UFER ground and a 3/0 copper to 4” underground water pipe.

 

[LarryFine]

You have a poor connection somewhere. Try taking fall-of-potential readings from point-to-point.

For example, look for voltage between the service neutral and the faulty panel's neutral.

 

[Scottybars2288]

You have a poor connection somewhere. Try taking fall-of-potential readings from point-to-point.

For example, look for voltage between the service neutral and the faulty panel's neutral.

i’ve checked all the feeder terminations and they’re good. I was hoping it would be on the power company but like i said within the house meter itself, I have continuity all the time. I dont know how it would be any of the branch circuits either unless i’m wrong.

 

[LarryFine]

The current of the branch circuits is exposing the problem, but not causing it, per se.

There is voltage between points where there shouldn't be an, a.k.a voltage drop (er, voltage rise?)

 

[Scottybars2288]

The current of the branch circuits is exposing the problem, but not causing it, per se.

There is voltage between points where there shouldn't be an, a.k.a voltage drop (er, voltage rise?)

it makes sense, I just have no idea where on my end this would be. All the bus in the meter banks is torqued, (snapped via manufacturer bolts) and i’ve checked the feeder and subfeed terminations. Is there anything else it could be or could it be the secondary neutral?

 

[LarryFine]

it makes sense, I just have no idea where on my end this would be. All the bus in the meter banks is torqued, (snapped via manufacturer bolts) and i’ve checked the feeder and subfeed terminations. Is there anything else it could be or could it be the secondary neutral?

That's why I'm suggesting FOP testing instead of visual inspections.

If you measure between the service neutral and the problem neutral (while under load), there must be a voltage difference. You just keep narrowing it down until you find the bad splice or connection.

So, even if you need a length of wire, measure for any voltage between the service neutral and the neutral where you're having the fluctuating readings. If you have that, you can find the problem.

It could be as simple as a wire in a lug, and there's voltage between the two, even though they feel tight.

 

[Scottybars2288]

That's why I'm suggesting FOP testing instead of visual inspections.

If you measure between the service neutral and the problem neutral (while under load), there must be a voltage difference. You just keep narrowing it down until you find the bad splice or connection.

So, even if you need a length of wire, measure for any voltage between the service neutral and the neutral where you're having the fluctuating readings. If you have that, you can find the problem.

It could be as simple as a wire in a lug, and there's voltage between the two, even though they feel tight.

makes sense, i’ll give this a shot

 

[Scottybars2288]

That's why I'm suggesting FOP testing instead of visual inspections.

If you measure between the service neutral and the problem neutral (while under load), there must be a voltage difference. You just keep narrowing it down until you find the bad splice or connection.

So, even if you need a length of wire, measure for any voltage between the service neutral and the neutral where you're having the fluctuating readings. If you have that, you can find the problem.

It could be as simple as a wire in a lug, and there's voltage between the two, even though they feel tight.

update, I lost my fluke a while back- and bought a milwaukee (don’t, pretty sure it sucks) I went and bought another fluke this morning, and tried this.
I have no voltage between the neutral in the meter, and the neutral at the panel (read 0.1v) It can’t be anywhere else either, it is a 250kcmil SER from the meter straight to the panel. I wanted a more accurate reading on the resistance hence why I went and bought another meter. at the panel I have anywhere from 1.5 to 2 ohms consistently with everything energized, and 0 with it de-energized .

 

[MD Automation]

Fyi... using an ohmmeter to read resistance while the conductors are energized will not give you valid readings.

Your meter has a battery and to get a measure of resistance in a circuit, that little battery causes some current to flow across whatever you are trying to measure. Then the meter reads the voltage drop it sees and turns that into a resistance measurement. This is a long way of saying that a standard ohmmeter is really measuring voltage - and using Ohm's Law to turn the measured voltage into a reading of ohms. And the source of that measured voltage MUST be from the meter's battery and ONLY the meter's battery.

So you don't want to use an ohmmeter with the power turned on. That introduces another source of voltage (however small) that will "confuse" (mathematically) the meter's reading.

As Larry indicated above - the better way of looking for problems here is to use your voltmeter to read FOP (Fall Of Potential) between 2 points you think should be at the same potential.

 

[MD Automation]

... I have anywhere from 1.5 to 2 ohms consistently with everything energized, and 0 with it de-energized .

And this is likely why you measure (correctly) 0 ohms with everything de-energized. The ohmmeter functions correctly with the power off.

Turning the power can cause some (very) small voltage drop in the conductor you are measuring (because there is now current flowing in it), but it's enough to screw up the meter's reading.