Home power lines all have current

Discussion in 'General Electronics Chat' started by atcrafts, Aug 5, 2009.

Aug 3, 2009
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After reading several posts I have two questions.I have been keeping track of my usage with a clamp-on ammeter on both the main power lines and each circuit. Let me give you a example of a reading on the 3 main lines, L1= 21.6 L2 =4.5 Neutral =8.3, from the posts I read this is out of whack. Second question do I add all these together to get total usage, and then do I drop down to the breakers and measure the black wires all together to see if they match

2. beenthere Retired Moderator

Apr 20, 2004
15,808
294
Your L1 & L2 phases should be close to balanced. That is a function of how many loads are on at one time and whether the breakers for those loads are on the L1 or L2 phase. The interesting part is the current on the neutral. All the current has to go back through the neutral line to complete the circuit. If your house were wired correctly, you should see 26.1 amps in the neutral - sum of the L1 and L2 currents.

Your breaker panel should have a big breaker at the top that interrupts all lines in. With it open, can you still read current on L1 off the pole? )If there is no disconnect inside, open all the breakers.) It would be interesting to see if neutral also shows current.

If L1 has current still, and neutral has none, I would immediately start looking for something or somebody stealing power. See if there is a heavy wire that leads off somewhere else other than your house.

Aug 3, 2009
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I have main breaker and I will try it as soon as I get home. How can I tell which line is L1?

4. beenthere Retired Moderator

Apr 20, 2004
15,808
294
Doubt if you can, unless it's still got current with the breaker panel disconnect opened - this is the distribution panel in your home, not the one out under the meter.

The mystery is the asymetrical current, and that is is so large in one leg. You will need to look for current outside at the utility pole in the lines that lead into the house. What you are doing is disconnecting the load (your house) but leaving the supply on. If there is still current under that condition, there is a problem that even an electrician should grasp.

Aug 3, 2009
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Flipped both breakers, no reading on any of the lines.

6. beenthere Retired Moderator

Apr 20, 2004
15,808
294
That would be the expected result for the disconnect at the meter. The thing to check for is current draw with the house disconnected and the utility drop on.

If nothing shows, then you need to meter each branch. If you feel confident enough, remove the breaker panel cover to access each branch line off the individual breakers. If they are marked, turn each on and see what kind of current is being pulled. Something has to show an abnormal draw.

Aug 3, 2009
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I have been metering each branch for the last couple of days. Let me give you the readings I got from yesterday from 4pm to 5pm according to my meter I used 6 KWH for that hour, my 3 mains read at 4pm 29.8, 11.1, 9.4, only 8 circuits had power, 2ton air both legs, 8.0, 8.2, I have a sub panel in my workshop about 100 feet from the house, it is 110 powered, 13.7 thats with a 6k btu a/c. Six other circuits 3.8, 1.8, .5, 1.1 ,1.2, .4 At 5pm the 6 circuits were the same, central a/c went to 13.9 one leg and 10.5 second leg and the workshop went up to 9.3; mains were 33.9, 20.0, 7.3.

8. t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
Given the individual line currents will be out of phase it's probably incorrect to do a simple algebraic addition to estimate the neutral current. Unless one knows the individual line current magnitudes and phases it is difficult to see how the neutral current can be determined other than by direct measurement.

9. t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
Did you get the neutral currents as well?

As an estimate, assuming all loads were purely resistive at 4pm - obviously not the case but it's a starting point ....

I1 = 29.8 angle 0° = 29.8 +j0 amps
I2 = 11.1 angle 120° = -5.55 +j9.6 amps
I3 = 9.4 angle 240° = -4.7 - j8.14 amps

In = 19.55 + j1.46 amps = 19.6 angle 4.3° amps

So a rough estimate of neutral current would be 19.6 amps on test. But as I said the loads aren't purely resistive so the estimate could be way off. Are you able to measure all four currents at some point?

Aug 3, 2009
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The 9.4 and 7.3 was the neutral readings.I am a novice I don't know what 4 currents you are referring to. The only meter I have is a ammeter, can I use that.

11. SgtWookie Expert

Jul 17, 2007
22,198
1,800
Actually, I don't think that's quite correct. I'd subtract the smaller L2 reading from the larger L1 reading; the neutral should be carrying the remaining current. If the current in L1 and L2 are equal and the loads are a similar type, you should have nearly zero current in the neutral line.

L1= 21.6
L2 =4.5
Remaining = 17.1
Neutral =8.3
8.8 Amperes unaccounted for.
Check your ground line to your grounding stake(s); there SHOULD be very little (if any) current in the ground line(s). If there is, you have a problem somewhere.

12. t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
OK - I see where I have mis-understood your situation. I thought you had a full 3-phase system rather than two phases & neutral - which you clearly stated.

13. t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
I agree with other gents that something looks very strange. No value of phase displacement in the line currents can account for the discrepancy.

14. BillB3857 AAC Fanatic!

Feb 28, 2009
2,471
381
I disagree with the above statement. Would it not be true that if the load on the two hot lines were perfectly balanced, there would be NO current in the neutral? Neutral will only carry the difference between the two individual line loads. Think of a center tapped 12v transformer feeding two 6v light bulbs in series. Measure the voltage between the center tap of the transformer and the "center" connection of the two lights. Minimal voltage difference, therefore minimal current.

OOOOPS>>>>>>> Should have gone to page 2 of the post before postsing. Sorry.

15. BillB3857 AAC Fanatic!

Feb 28, 2009
2,471
381
After reading SgtWookie's post, a ground fault (something returning power to a water pipe, etc) could be causing an unmeasurable current path. How about a sump pump or deep well pump?

Aug 3, 2009
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OK now I am starting to get scared and pissed. I tested the ground stakes I have two of them both side by side, one reads 3.1 amps goes to the gas line one reads 1.9 amps to the water line. I did have only one till about a year ago when I hired a electrician to look at the problem.He rewired my sub panel in the workshop saying it was wired incorrectly, then he said the ground rod on the house was wrong, it was wired to my meter box but not to any of the pipes in the back of my house. I justed pulled the cover off the sub panel box and my neutral bus is cut into two parts one is still attached to the box the other is just hanging in the air. The box is made of plastic.Also should the sub panel have a ground rod.

Jul 7, 2009
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It does sound strange. I would recommend you start over with a carefully-made diagram and mark it with all the readings you get. Go back later and verify the readings too.

Check your ammeter to make sure it's reading things sensibly. One way to do this check is to use a digital multimeter's 10 A current scale. To do this, you should feel comfortable breaking 120 VAC lines and inserting an ammeter and know how to do it safely. You're making measurements to make decisions, so make sure the measurements make sense.

The advantage of having everything documented is that you'll have something to show an electrician should you feel it's necessary to get a professional to look things over. You can make the measurements again after any work is done and see if there's a difference. Of course, they're only meaningful if you know the loads were the same. A 1 kW or so electric heater can make a good load.

Finally, a carefully-made diagram will be valuable here should you post it -- they always make it easier to understand an electrical problem.

18. SgtWookie Expert

Jul 17, 2007
22,198
1,800
Wait a minute - you say you have 3.1 Amperes of current on a ground line that goes to a NATURAL GAS LINE?

I am NOT a licensed electrician. However, 3.1 amps flowing through a natural gas line just does not sit well with me at all!

You really need a licensed electrician to come out and look at your situation.

One thing you might do is to turn off the blower motor in your air handler, and see if the current in the gas line ground goes away. If it does, someone may have replaced a 240v blower motor with a 120v motor, and improperly used the ground line as a neutral return line. This would be a very bad thing, because:
1) Replacing a 240v motor with a 120v motor of the same rated HP will double the current in the circuit. This results in a much higher voltage drop across the wiring, and loss of power due to heat in the wiring.
2) The ground wire is typically a much smaller gauge wire, and would not be able to handle the current.

Ground wires should never carry any appreciable level of current. They exist to protect humans from exposure to high voltages, in case there is a fault somewhere.
There are many national, state and local electrical codes that have to be complied with. Only a licensed electrician is qualified to give you a correct solution to your situation. They're not exactly cheap, but compared to having your home and workshop turned into a blazing fireball, they're a remarkable bargain.

As I've already said a couple of times, I'm not a licensed electrican. Years ago (1960's and earlier) it was typical for electricians to use a copper water main for an earth ground. I have no idea when the electrical code changed, but later the requirement was to have an an 8 1/2' copper clad rod pounded into the ground, with a suitably-sized (typically AWG 4) solid conductor clamped to it, and run to the electrical service panel. Sometime later that was amended to require TWO grounding rods driven in at least some distance apart. I don't know what the minimum distance is offhand; I think it's six feet, but an electrician would know for sure.

I have no clue why the electrician cut the neutral bus in your sub panel. It doesn't sound right to me, but ... I'm not a licensed electrician.

Whether your sub panel needs it's own ground rod(s) might depend on how far it's located from the main panel - but a licensed electrician will be able to tell you whether you need one or not.

Check to see if there is current in the ground line coming back from the sub panel to the main service panel.

The current in the gas line is a great cause for concern.
I don't like the 1.9A in the water line, either.