Open neutral

Status
Not open for further replies.
M

Matt Mckenzie

Member
Location
United States
20 amp 120volt circuit tests open neutral. 120volt hot to grounding but no hot to neutral. Also when you test neutral to grounding wiggy tests 120v to grounding. Phase to phase nothing. Does anybody know what might cause this? There is construction going onsite. I cant find the problem.
 
you actually found the problem... check the next j-box towards the panel, its just bad make up under the neutral wire nut. (assuming all whites in the panel are ok..)
 
Does everything else work? Check your gfci or any connections back to the panel.

When you said phase to phase then where are you testing that? I assume you meant phase to neutral....
 
Matt Mckenzie said:
20 amp 120volt circuit tests open neutral. 120volt hot to grounding but no hot to neutral. Also when you test neutral to grounding wiggy tests 120v to grounding. Phase to phase nothing. Does anybody know what might cause this? There is construction going onsite. I cant find the problem.
Click to expand...


You can't get 0 phase to phase if you're getting 120V hot/phase to ground (EGC). If you had lost one leg, you would at least get 120V phase to phase when checking. Sounds like you just need to find where you lost the neutral.
 
181007-1647 EDT

Matt Mckenzie:

Your description does not seem to imply a lost neutral, but rather a neutral that is connected to your hot wire. Lost assumes there are no conductive loads between HOT and NEUTRAL in the area of the measurement point.

I believe "grounding" means EGC. I will assume the EGC is good and connected to neutral at the main panel. It appears HOT is reasonably good back to the main panel.

I will assume your voltmeter is a high impedance DVM. The wiggy is a low impedance crude voltmeter.

You measured 120 V from HOT to EGC with the DVM, and 0 or near 0 from HOT to NEUTRAL with the same meter. If NEUTRAL was lost, meaning floating, then with a high impedance meter you would read some intermediate voltage between around 60 V +/-50 V from capacitive coupling. But you read essentially zero meaning HOT and NEUTRAL are essentially connected together.

With the wiggy, a low impedance, you see 120 from NEUTRAL to EGC. This implies NEUTRAL is connected to HOT.

Turn all breakers off except for the one to your circuit. Are your measurements from NEUTRAL to the other points still the same? Assume yes.

Make a long test lead from the main panel neutral to anywhere that you will measure voltage. An extension cord can be used.

I assume there are a number of outlets on this circuit.

Connect a 1500 W heater between the bad NEUTRAL and some known good neutral. Could use another extension cord to the main panel. This will provide about a 10 A load at 120 V.

Two things can be done now. Using a sensitive gauss meter you can trace the current path of the bad NEUTRAL. Second voltage measurements between the neutral on other outlets on your circuit and the test lead neutral will point you to the general area where the problem may exist. The problem is between or at the main panel or the first outlet, or between or at two other outlets.

Some voltage difference measurements with the DVM and the 10 A load may prove useful.

I don't known if the above is clear, but I believe you have a pretty solid connection between your bad NEUTRAL and some hot wire.

.
 
gar said:
181007-1647 EDT

Matt Mckenzie:

Your description does not seem to imply a lost neutral, but rather a neutral that is connected to your hot wire. Lost assumes there are no conductive loads between HOT and NEUTRAL in the area of the measurement point.

I believe "grounding" means EGC. I will assume the EGC is good and connected to neutral at the main panel. It appears HOT is reasonably good back to the main panel.

I will assume your voltmeter is a high impedance DVM. The wiggy is a low impedance crude voltmeter.

You measured 120 V from HOT to EGC with the DVM, and 0 or near 0 from HOT to NEUTRAL with the same meter. If NEUTRAL was lost, meaning floating, then with a high impedance meter you would read some intermediate voltage between around 60 V +/-50 V from capacitive coupling. But you read essentially zero meaning HOT and NEUTRAL are essentially connected together.

With the wiggy, a low impedance, you see 120 from NEUTRAL to EGC. This implies NEUTRAL is connected to HOT.

Turn all breakers off except for the one to your circuit. Are your measurements from NEUTRAL to the other points still the same? Assume yes.

Make a long test lead from the main panel neutral to anywhere that you will measure voltage. An extension cord can be used.

I assume there are a number of outlets on this circuit.

Connect a 1500 W heater between the bad NEUTRAL and some known good neutral. Could use another extension cord to the main panel. This will provide about a 10 A load at 120 V.

Two things can be done now. Using a sensitive gauss meter you can trace the current path of the bad NEUTRAL. Second voltage measurements between the neutral on other outlets on your circuit and the test lead neutral will point you to the general area where the problem may exist. The problem is between or at the main panel or the first outlet, or between or at two other outlets.

Some voltage difference measurements with the DVM and the 10 A load may prove useful.

I don't known if the above is clear, but I believe you have a pretty solid connection between your bad NEUTRAL and some hot wire.

.
Click to expand...

If the neutral is connected at the panel (bus bar containing the main neutral/grounded) you would have a direct short if the neutral and hot were connected. OP may have another problem instead of a lost neutral but I don't see how it could be hot-neutral connected. If that is the case, it goes back to "lost neutral" as it would have to be disconnected/loose at the panel or is broken past the panel but before the point of measurement.
 
181007-2206 EDT

Little Bill:

With the information provided in post #1 the NEUTRAL at the point of measurement is connected to a HOT wire somewhere, and does not have continuity back to the neutral in the main panel, or any other neutral that is good to the main panel. This is based on the DVM reading full hot voltage at the point of measurement, and that the wiggy a moderately low impedance, which seems to read full 120 from subject NEUTRAL to EGC.

.
 
gar said:
181007-2206 EDT

Little Bill:

With the information provided in post #1 the NEUTRAL at the point of measurement is connected to a HOT wire somewhere, and does not have continuity back to the neutral in the main panel, or any other neutral that is good to the main panel. This is based on the DVM reading full hot voltage at the point of measurement, and that the wiggy a moderately low impedance, which seems to read full 120 from subject NEUTRAL to EGC.

.
Click to expand...

So, still a lost neutral if no continuity back to the panel.
 
Little Bill said:
If the neutral is connected at the panel (bus bar containing the main neutral/grounded) you would have a direct short if the neutral and hot were connected. OP may have another problem instead of a lost neutral but I don't see how it could be hot-neutral connected. If that is the case, it goes back to "lost neutral" as it would have to be disconnected/loose at the panel or is broken past the panel but before the point of measurement.
Click to expand...

I agree. This is a lost neutral. If this is a 120v plug l would kill the circuit take extend my lead and ohm the neutral out in the surrounding plugs until I didn’t have continuity. This isn’t rocket science it is a house most likely(more information from the OP would be helpful ). However in my opinion a length of number 12 and a continuity test would most likely find the problem.


Sent from my iPhone using Tapatalk
 
181007-2357 EDT

Little Bill:

We have rather incomplete information from post #1.

We have a subject NEUTRAL that is clearly not presently connected to neutral at the main panel. For the measurements presented there are two possibilities. One that said subject NEUTRAL is directly connected to a HOT somewhere instead of to a neutral going to the main panel. Or. Two that said subject NEUTRAL is open and floating, but that there are conductive loads from said subject NEUTRAL to a HOT somewhere.

A 1500 W heater load between subject NEUTRAL, and some known good neutral will probably identify which of the two cases exists.

.
 
The OP has described what we search for in the USA when we run Continuity of Conductor tests. He has somewhere switched the neutral with the live wire. One of the outlets is wired on the wrong side on one end. Thus, his neutral wire has become the live wire from that point. Just trace what outlet the live to ground no longer gives you 120... open the outlet before that up and make sure the wiring is correct... if it is not correct, fix it. If it is correct, the outlet that was wrong was the one miswired, on the load side.
 
Matt Mckenzie said:
20 amp 120volt circuit tests open neutral. 120volt hot to grounding but no hot to neutral. Also when you test neutral to grounding wiggy tests 120v to grounding. Phase to phase nothing. Does anybody know what might cause this? There is construction going onsite. I cant find the problem.
Click to expand...

ok, stand corrected. If hot to neutral is zero but hot to ground and neutral to ground are both showing 120 then he has combined the hot and neutral somewhere... but if breaker and other neutrals not showing the 120 to ground problem then he has somehow either lost the neutral and is using the second wire of an mwbc circuit as his neutral, or i am totally confused now. I need coffee.
 
Adamjamma said:
ok, stand corrected. If hot to neutral is zero but hot to ground and neutral to ground are both showing 120 then he has combined the hot and neutral somewhere... but if breaker and other neutrals not showing the 120 to ground problem then he has somehow either lost the neutral and is using the second wire of an mwbc circuit as his neutral, or i am totally confused now. I need coffee.
Click to expand...

Coffee always helps my concentration by widening its borders. Suddenly the trash needs emptied on the way to the RR, Whoa when did that weed sprout next to the dumpster, where did I leave my mug, I’ll get decaf and no donuts this time.

Zero volts phase to phase might mean he only has a 120v service to his temporary. Another P&R thread.
 
Adamjamma said:
If hot to neutral is zero but hot to ground and neutral to ground are both showing 120 then he has combined the hot and neutral somewhere...
Click to expand...

That is exactly what you should read if the neutral is open before getting back to the source. Draw the circuit out, the path starts at L1----goes through overcurrent devices, switches, etc, ----- then the load-----then the neutral conductor connected to the load, but path stops wherever the neutral conductor is open, at this point you have full voltage to source neutral as well as to ground if the source neutral is grounded.
 
kwired said:
That is exactly what you should read if the neutral is open before getting back to the source. Draw the circuit out, the path starts at L1----goes through overcurrent devices, switches, etc, ----- then the load-----then the neutral conductor connected to the load, but path stops wherever the neutral conductor is open, at this point you have full voltage to source neutral as well as to ground if the source neutral is grounded.
Click to expand...

Exactly right.
 
Adamjamma said:
ok, stand corrected. If hot to neutral is zero but hot to ground and neutral to ground are both showing 120 then he has combined the hot and neutral somewhere....
Click to expand...

its... connected at the panel...the whitey is gapped... he gets 120 to the bare. that is a situation that can hurt if theres a load at the problem location, then some poor guy grabs the neutral. and people say the white doesn't kill...
 
Status
Not open for further replies.
Top