DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (http://www.diychatroom.com/)
-   Electrical (http://www.diychatroom.com/f18/)
-   -   Electrical mystery - current on ground! (http://www.diychatroom.com/f18/electrical-mystery-current-ground-168245/)

braverichard 01-04-2013 03:28 PM

Electrical mystery - current on ground!
 
I'm troubleshooting an issue at a house and came across the following rather odd circumstances. I pulled in an electrical contractor with 33 years of experience and even he was dumbfounded and had no answers (said he'd consult other electricians). Just seeking ideas from where ever I have access.

-House is a regular ranch home in the US Midwest with a 100AMP service. Off the bat, we measured the power supply as 244V not 240V (I know it fluctuates as you measure it, but in my 10 years of working on houses I've never seen it go outside the 239-241V range).

-The power supply is not balanced for some reason: One leg on this house has 130V and the other 114V. The current on the neutral is much less than the difference between the currents on the two legs. Specific example: leg 1 had 28A and leg 2 had 4A yet the neutral was not 24A (28-4) it was 18A. Then I checked for current on the ground and baam - the ground was carrying about 6A. Yet I can touch the ground and not get shocked! I measure the voltage on the ground and it is 0V. I verified this to be a good earth ground.

-Initial suspicion was that one of the outlets in the house is wired incorrectly with the neutral going to the ground and vice versa but I checked all the ground wires coming to the panel and none were hot.

Anyone ever experienced anything like this? Any ideas? I'm really confused by how the meter was showing 6A on the ground for the service yet no volts?!? How can there be current without voltage? Or is the voltage so low (less than 0.01V) that my meter could not show it?

jbfan 01-04-2013 03:32 PM

Well pump or city water?

rjniles 01-04-2013 03:37 PM

Electric water heater with a bad element. Turn the WH breaker off and retest.

If not that turn all breakers off and retest. Turn breakers on 1 at a time until problem gomes back.

braverichard 01-04-2013 03:42 PM

The issues I described were found at the breaker panel, not on a specific circuit. These are issues with the entire service to the house.

City water. The house however does not have a cold water ground, just an earth ground (old house, old code, current code requires two grounds, cold water supply and earth).

House has no electric water heater.

I like rjniles' idea, just might try that.

jcrack_corn 01-04-2013 06:14 PM

bad meter/meausuremt? v=ir so yes, the voltage cant be zero. what about bad neutral from the house to the pole or somewhere in POCO system....just faulty, not completely bad... so that during a portion of the 60hz wave the neutral is not functional (possibly getting hot at a near broken connection, so resistance shoots up), the ground becomes best path to POCO for that cycle or two, then the neutral cools....etc etc...replayed over many times a second. the meter may not have enough resolution to determine the true RMS voltage if this is happening quickly.... just a guess

diystephen 01-04-2013 06:23 PM

I like rjniles' approach. Kill all the breakers and retest. This is a good way to determine where the problem resides (POCO or house.)

k_buz 01-04-2013 06:35 PM

Get a different electrical contractor.

Stubbie 01-04-2013 06:37 PM

Quote:

Originally Posted by braverichard (Post 1086278)
The issues I described were found at the breaker panel, not on a specific circuit. These are issues with the entire service to the house.

City water. The house however does not have a cold water ground, just an earth ground (old house, old code, current code requires two grounds, cold water supply and earth).

House has no electric water heater.

I like rjniles' idea, just might try that.

Bad utility neutral in your service drop to the weather head. Go outside and look at the neutral from the weather head to the transformer and look for broken strands. Your neutral will look like a wire rope. Have you been noticing any dimming and brighting with your lights?

rrolleston 01-04-2013 07:30 PM

I would also turn all the breakers off including the main and slowly turn on breakers till you get the voltage. If you get it without the main on then something is happening between your panel and the weather head.

Edit:

I have seen as high as 127 on one leg here. Usually hangs around 120-125 though.

av-geek 01-04-2013 07:40 PM

You will not get any voltage measurement on the ground or the neutral legs, because they are at earth ground potiental, even if there is power flowing onto these legs. The amperage you are seeing is flowing from the hot legs, through the loads and then onto the ground and neutral legs, thus indicating on your meter. The voltage difference you are seeing may be the result of there being different loads on the different legs. More load could be causing a voltage drop. Use RJNiles approach, and turn off all the breakers, measure the voltage at the two hot legs coming in, and then start from there. IF the voltage is till not balanced with no load on at the house, contact the power company to repair the transformer. If you do get balanced voltage, proceed to the next step and turn on each individual circuit while measuring voltage and current to see when the problems develop

mpoulton 01-04-2013 09:08 PM

Get a different electrician. The voltage imbalance between the service legs is a clear indication of a bad service neutral connection. The current on the ground conductor is another symptom of that. Current on the water pipe bonding wire is normal if you have city water with metal piping between houses - some current will return to the utility through your neighbor's water piping, which is fine. However, any current on the grounding ELECTRODE conductors (wire to ground rods or slab rebar) is always abnormal and often indicates a loose neutral, like you have.

This is a fairly serious problem, and it needs to be fixed ASAP. It will get worse. Much worse. Maybe suddenly. When it does, it can destroy every electronic device in your home simultaneously, and can cause weird shock hazards like electrified water piping. So get a competent electrician to handle it very soon!

braverichard 01-05-2013 06:47 PM

Thanks all for your suggestions. Your ideas are all very neat and make sense. This is a house I rented out so I scheduled a time to go back and execute the ideas you've all suggested for this coming Saturday. I will be sure to update you all with my findings.

Other electrical contractors are telling me they feel a bad neutral may be the cause but I will check first.

Quote:

Originally Posted by k_buz (Post 1086423)
Get a different electrical contractor.

And how exactly is that supposed to help me? I don't get ya.

k_buz 01-05-2013 06:50 PM

A competent electrical contractor would have been able to diagnose and troubleshoot this problem. It isn't all that uncommon.

kbsparky 01-05-2013 08:27 PM

The neutral current will not always be the difference of the 2 legs. That would only apply if all loads were 120 Volt. You can have 240 Volt loads that would not have any neutral current.

As for the voltage differences in the 2 legs, you have a bad neutral connection somewhere in the supply chain.

My system voltage here is 125/250. A bit on the high side but that's the way its always been here.

dmxtothemax 01-05-2013 11:25 PM

Quote:

Originally Posted by braverichard (Post 1086263)
I'm troubleshooting an issue at a house and came across the following rather odd circumstances. I pulled in an electrical contractor with 33 years of experience and even he was dumbfounded and had no answers (said he'd consult other electricians). Just seeking ideas from where ever I have access.

-House is a regular ranch home in the US Midwest with a 100AMP service. Off the bat, we measured the power supply as 244V not 240V (I know it fluctuates as you measure it, but in my 10 years of working on houses I've never seen it go outside the 239-241V range).

-The power supply is not balanced for some reason: One leg on this house has 130V and the other 114V. The current on the neutral is much less than the difference between the currents on the two legs. Specific example: leg 1 had 28A and leg 2 had 4A yet the neutral was not 24A (28-4) it was 18A. Then I checked for current on the ground and baam - the ground was carrying about 6A. Yet I can touch the ground and not get shocked! I measure the voltage on the ground and it is 0V. I verified this to be a good earth ground.

-Initial suspicion was that one of the outlets in the house is wired incorrectly with the neutral going to the ground and vice versa but I checked all the ground wires coming to the panel and none were hot.

Anyone ever experienced anything like this? Any ideas? I'm really confused by how the meter was showing 6A on the ground for the service yet no volts?!? How can there be current without voltage? Or is the voltage so low (less than 0.01V) that my meter could not show it?


If you have a split supply,
the for it to be balanced then you would
need to have exactily the same load on each hot line !
Very unlikely.
To confirm, put an clamp on ammeter on each hot supply,
Good chance that the lower one has more load on it !
The current in the earth line could be due to unbalanced load,
or a bad connecttion somewhere.
Try turning off circuits and see what happens to the meter reading.
And measuring from earth to earth will always give no reading.


All times are GMT -5. The time now is 06:26 AM.


Copyright 2003-2014 Escalate Media LP. All Rights Reserved