Amp meter Results - SE Cable Bad or Power CO - DIY Chatroom

jamiedolan · 01-19-2009, 12:44 AM

I have tested the amps on the ground / bond wire connected to the water pipe with the load off in my parents house. When the load is off or very low, I get 0 amps on the water pipe connection. When I added a 12 amp load from a heater, it put out about 2.5A on the water pipe connection.

I tested Neutral to each leg of the panel with my Ideal RMS meter. I am getting about 1.5v less on one leg of the panel with a nominal load (few amps on whole house). Once I add in the heater, I saw more like a 3 volt difference between the 2 legs of the panel. (The neutral is securely clamped down in the panel).

So should I be thinking service entrance cable, service drop, or could the butt splices the power co made when reconnecting the power last week be bad?

When I tested the power for the fist time after the power co reconnected it, I read about 123.5v on both legs. Prior to the disconnect, I was reading a couple vots less. Not sure why the change, or if it is meaningful. I suspected it could have been a result of the electrician tightening the main lugs on the panel while the power was off (due to a slightly better connection now with them tightened).

I have visually inspected the se cable and there is no visable damage. Do you think it's work calling the power co on this or is this more likely service drop / service entrance cable that needs to be replaced, due to damage

What you your next step in testing be at this point?

Thanks

Jamie

WFO · 01-19-2009, 12:56 AM

Quote:

Originally Posted by jamiedolan

I tested Neutral to each leg of the panel with my Fluke RMS meter. I am getting about 1.5v less on one leg of the panel with a nominal load (few amps on whole house). Once I add in the heater, I saw more like a 3 volt difference between the 2 legs of the panel. (The neutral is securely clamped down in the panel).

Assuming the heater is 240 volts, the added load should have affected the voltage identically on each leg ( barring any loose connection or other wiring problem)....however, you would need to be certain nothing else was cut on on one leg or the other during the course of your test.

Quote:

Originally Posted by jamiedolan

When I tested the power for the fist time after the power co reconnected it, I read about 123.5v on both legs. Prior to the disconnect, I was reading a couple vots less. Not sure why the change, or if it is meaningful. I suspected it could have been a result of the electrician tightening the main lugs on the panel while the power was off (due to a slightly better connection now with them tightened).

Jamie

POCO's have voltage regulators on the line that automatically raise and lower voltage according to voltage and/or load ......depending on where you are on the line, your voltage can vary "normally" several volts during the day.

jamiedolan · 01-19-2009, 01:03 AM

Quote:

Originally Posted by WFO

Assuming the heater is 240 volts, the added load should have affected the voltage identically on each leg ( barring any loose connection or other wiring problem)....however, you would need to be certain nothing else was cut on on one leg or the other during the course of your test.

I apologize for not providing more details. It was a simple 120v heater, I put on just as a test to see what happened if I drew more power on one leg of the panel. ... So it was only drawing on one leg of the panel. The connections to the outlet, breaker and neutral bar from the outlet are all good.

Thanks
Jamie

InPhase277 · 01-19-2009, 03:23 AM

Jamie, 2.5 A sounds like a lot to me. Some current must naturally flow into the earth, by nature of how we ground our services, but I don't think that much. Try this: clamp the meter on the pipe, at each side of the bond clamp. Tell us what you see.

Yoyizit · 01-19-2009, 02:14 PM

Post a wiring diagram (not a schematic) of what you think you have, with approx. resistances of the current paths showing.
E=IR will tell what is good or bad.

With all the meters you have now and only linear loads (no computers) this should be easy.

jamiedolan · 01-19-2009, 02:58 PM

Quote:

Originally Posted by InPhase277

Jamie, 2.5 A sounds like a lot to me. Some current must naturally flow into the earth, by nature of how we ground our services, but I don't think that much. Try this: clamp the meter on the pipe, at each side of the bond clamp. Tell us what you see.

Putting the clamp meter on the pipe (either side of the clamp) or the wire just now gets me a reading close to 0 amps.

I turned on a 12amp 120v heater, and tested both on the wire on the pipe (right next to the meter) and on the pipe (either side of the clamp) itself. I get about 4 amps on the water pipe in both positions and floating between 2 and 3 amps on the wire. When I turn the heater off, it goes back to close to 0. There are some other loads currently running here, nothing large.

Could it be a problem with just one leg of the panel? Also when I turn on that same heater, and test the voltage on the main unfused lugs, prior to the main fuse, I see about a 2 volt drop, ongoing while that heater is running, but only on one leg of the panel. This is 200A service. Seems very odd to me that a 12A heater could cause the main to drop by 2v continously.

Thanks
Jamie

Yoyizit · 01-19-2009, 03:55 PM

2v/12A = 1/6 ohm.
If the other side went up by 2v (a 4v diffference between each 120v side) you should see 2v across the neutral connection/wiring, and if you do it is bad.
These measurements should be at the panel, not at the outlets.

2v(12A)=24W; even with the heat being carried away with all the busbars the connection might look warm on an IR meter.

Any bolted connection should have less than 1mV across it.

rgsgww · 01-19-2009, 04:24 PM

Seems like you have a loose connection somewhere...maybe water got in those butt splices and pushed them apart?

InPhase277 · 01-19-2009, 05:27 PM

Quote:

Originally Posted by jamiedolan

I get about 4 amps on the water pipe in both positions and floating between 2 and 3 amps on the wire.

Thanks
Jamie

This doesn't make alot of sense... Take the wire loose from the clamp. Measure the voltage between the wire and the pipe. Then measure how much current is flowing in the pipe with the wire still unattached.

Where is the water meter in relation to the pole that serves the house?

Yoyizit · 01-19-2009, 07:41 PM

You can measure a larger chunk of the neutral connection by measuring the voltage from your panel housing to the meter housing.

jamiedolan · 01-19-2009, 09:34 PM

Quote:

Originally Posted by InPhase277

This doesn't make alot of sense... Take the wire loose from the clamp. Measure the voltage between the wire and the pipe. Then measure how much current is flowing in the pipe with the wire still unattached.

Where is the water meter in relation to the pole that serves the house?

The pole that serves this house is about 80-'100' away. The panel inside the house in about 12' from where the water enters the house.

I will take measurement and report back. Thank You.
Jamie

InPhase277 · 01-19-2009, 09:55 PM

Quote:

Originally Posted by jamiedolan

The pole that serves this house is about 80-'100' away. The panel inside the house in about 12' from where the water enters the house.

Jamie

I mean, where is the transformer pole in relation to the water meter? I assume the water meter is located near the street. What I'm driving at is, if the pole and water meter are close together, then it is possible that the resistance is small enough that a substantial current could flow along the water line to the utility ground at the transformer.

jamiedolan · 01-19-2009, 10:20 PM

Quote:

Originally Posted by InPhase277

I mean, where is the transformer pole in relation to the water meter? I assume the water meter is located near the street. What I'm driving at is, if the pole and water meter are close together, then it is possible that the resistance is small enough that a substantial current could flow along the water line to the utility ground at the transformer.

I will go out and look and see if I can tell where exactly the transformer is that serves this house. I think it maybe on the pole that the service drop come from that is about 80' away, I will check.

Tests Results:

4# while connected to water no voltage reading between pipe and wire
4# when disconnected no voltage reading between pipe and wire

When 4# is connected durring most current test, with clamp meter* around water pipe, and #4 bonding pipe to panel, there was around .5 amps.

When 4# is disconnected with clamp meter around water pipe as above, and a 120v (12A draw) heater is turned on, clamp meter now reads about 4.5A. Service neutral saw increase of right about 7.5A. Net results return current from a 12A heater.

When I reattached the 4# to the water line (at water meter) with the heater running and clamp meter on the water pipe, I saw an increase of about 1A to about 5.5A on the water pipe.

Grounding rod 6# wire read little to no amps durring any of these tests.

I am a bit confused as to how and why we are returning so many amps via the water system, even when I physically disconnect the #4 wire that bonds it to the panel. (I am sure it is connected to the ground system elsewhere, but can't see how that is the path of least resistance for the current to return to the transformer).

*Note: Readings taken with a new True RMS clamp meter.

Thanks
Jamie

jamiedolan · 01-19-2009, 10:28 PM

The transformer is 2 poles away and across the intersection, likely closer to 150' - 200' from water meter to pole transformer that serves us.

Thanks
Jamie

InPhase277 · 01-20-2009, 12:11 AM

There is something screwy with the plumbing! What other paths are there between the panel and water line within the house? Somewhere neutral current is finding it's way to the water line. Where is the heater you are plugging in? Is it right by the panel, or a branch circuit in the house? And have you tried on different circuits? I know I'm asking alot of questions, but we have to get to the bottom of this. Fill in the blanks in the pics, if you don't mind.