The problem with the measurement is that in a main panel, where the neutral and ground are bonded, you cannot just clamp the neutral to the meter and get a complete measurement because there are other paths available via any ground path. In the main panel, you would need to clamp all the individual branch circuit neutrals. If it is a subpanel, you can clamp the neutral and get an accurate reading.
Neutral not carrying unbalanced load
- Thread starter shk1101
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Joethemechanic
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that is the amount of current you'd have flowing with a bolted fault L to ground if the ground rod was a little iffy (30 ohms)
A 120 volt leg connected directly to a 25 ohm ground electrode would only flow 4.8 amps
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That’s only true if the only GEC path terminates in the earth. If the grounding electric system includes, for example, a water pipe connected to a municipal water system, the GEC could carry the entire neutral load.
Joethemechanic
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Yeah I have seen that. But the point is, he has 3-4 amps on the grounding electrode conductor. Seems kind of excessive
I'm thinking high impedance neutral
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ptonsparky
Tom
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The OP currents work pretty well if the source is actually three phase and not single. 19 vs 11 amp neutral load.
Oops, NM, I used 22 vs 32.
Oops, NM, I used 22 vs 32.
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if he has 10 amps of line to line loads, he would have 1 amp of line to neutral load on line A, and 22 amps of line to neutral load on line B, making the neutral current 21 amps.
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Given the original numbers I would be expecting to see 11 amps on the GEC.
Joethemechanic
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Maybe there is a bond or bonds carrying the other 7 amps
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About the only outside path for that amount of current would be a common metal underground water piping system. That could occur with a neutral to interior metal water pipe bond on the load side of the main bonding jumper. Such current would show on the water pipe. but not the GEC.
The OP needs to check the current on the water pipe itself.
Seven-Delta-FortyOne
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I need to get my eyes checked. I read 22, not 32. My bad.
gar
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230715-1646 EDT
shk1101:
Can you approximately replicate your measurements of post #1:
If so, then there are several things to try.
First, verify that this is source from a single phase. If it is, then ( L1-N ) + ( L2-N ) will equal ( L!- L2 ) where - equals to.
Repeat your original experiment.
Open all two pole breakers except the main.
Open all single phase L2 breakers, L2 should read 0 current, and close all L1 single phase breakers. L2 should read 0 current, and L1 and neutral should both read the same.
Open all single phase L1 breakers, L1 should read 0 current, and close all L2 single phase breakers. L1 should read 0 current, and L2 and neutral should both read the same.
Open all single pole breakers, and close all 2 pole breakers. Measure L1, L2, and neutral currents.
Presents your results.
.
shk1101:
Can you approximately replicate your measurements of post #1:
If so, then there are several things to try.
First, verify that this is source from a single phase. If it is, then ( L1-N ) + ( L2-N ) will equal ( L!- L2 ) where - equals to.
Repeat your original experiment.
Open all two pole breakers except the main.
Open all single phase L2 breakers, L2 should read 0 current, and close all L1 single phase breakers. L2 should read 0 current, and L1 and neutral should both read the same.
Open all single phase L1 breakers, L1 should read 0 current, and close all L2 single phase breakers. L1 should read 0 current, and L2 and neutral should both read the same.
Open all single pole breakers, and close all 2 pole breakers. Measure L1, L2, and neutral currents.
Presents your results.
.
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