Neutral not carrying unbalanced load
- Thread starter shk1101
- Start date
chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
AC running?
Dryer?
Water heater etc?
Dryer?
Water heater etc?
TwoBlocked
Senior Member
- Location
- Bradford County, PA
- Occupation
- Industrial Electrician
Either a ground current, an additional neutral path, or a bad reading. Be sure the clamp on the meter is completely closed. Try to have the conductor in the center of the clamp opening.
- Location
- Illinois
- Occupation
- retired electrician
Loads cycling between your A and B measurements?
If your measurements of the A and B leg of the phase are accurate, then I guarantee you that 22A is making it back to the transformer neutral point. The question is how many paths is it taking and what are they.
But I don't think your measurements are accurate. Assuming you checked for voltage and both legs were 120v to neutral, it would mean that you have an alternative path back to the transformer that is better than the intended neutral by being able to carry more than half of the current.
It would make sense if you had a bad neutral, but then you would see a voltage mismatch between the legs and neutral.
- Location
- Illinois
- Occupation
- retired electrician
Maybe not if the area has a common metal underground water piping system and multiple services are bonded to that system as required by the code. It is not unusual to find 20% or more of the neutral current on the water system even where the neutral is in perfect shape. You can have a completely open service neutral without any voltage mismatch where the metal water pipe is carrying the neutral current.
Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
Because none of your 240V loads will have current on the neutral.
Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
However, your numbers still don’t add up, so there is something else going on.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Check the current on the GEC.
I checked the voltage everywhere and got correct voltages
I check GEC too and it only had 3-4 amps.
I'm not concerned about the 240v. I'm curious about why I'm not getting the difference sent back to my neutral.
ptonsparky
Tom
- Occupation
- EC - retired
Clamp all the incoming conductors at the same time. What is it?
I don't know then what the issue is, but it's physics. Your original thoughts are solid.
What ever the current leaving on one leg will equal exactly the sum of what's returning on the other leg and the neutral.
And if you are saying that the voltage on each leg to neutral is balanced 120/120 at the same time you are carrying an unbalanced load of that magnitude means you have a solid connection to the source neutral. But the only way that can happen is if you have a parallel path back to the transformer neutral point that is more effective than your service neutral. Which blows my mind.
If it were the other way around it would make more sense, you will always have a trickle coming back on the ground rod of the house to the ground at the source through the earth, but your numbers mean the alternate path is better than the intended path.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
230710-1933 EDT
shk1101:
chris kennedy answered your question in post #2.
.
shk1101:
chris kennedy answered your question in post #2.
.
- Location
- Illinois
- Occupation
- retired electrician
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
230710-2136 EDT
don resqcapt19:
I misread the question in terms of your analysis. I had thought that the measurements of the 120 V loads were given which would have excluded 240 loads, but your interpretation is more likely correct.
.
don resqcapt19:
I misread the question in terms of your analysis. I had thought that the measurements of the 120 V loads were given which would have excluded 240 loads, but your interpretation is more likely correct.
.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
Are the service conductors run through metallic conduit between the panel and a meter? If so, perhaps there's a N/G bond at both the panel and meter. That could provide a parallel path for neutral current.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
This is the approach I would take.
When you clamp multiple conductors at the same time, you measure the net current flow. In other words, the physics does the math for you.
In addition to the possibility of current flowing on the GEC, you might also be seeing measurement error because of waveform shape.
Or you might have loads that changed between your various measurements.
Clamping all the circuit conductors at the same time gives you a measure of the net current after instantaneous addition of the component currents.
Jon
Seven-Delta-FortyOne
Goin’ Down In Flames........
- Location
- Humboldt
- Occupation
- EC and GC
Well you should be.
Because none of your 240V loads will send *anything* back on the neutral.
Just based on the numbers you have posted, you could theoretically have 10 amps of 240V loads, 12 amps of 120 L-N loads, with 9A on the neutral and 3 on the EGC.
All I’m going off of is the numbers. You haven’t told us anything about the existing loads.