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#49787 - 03/17/05 08:23 AM Hot Ground Question?
JFLS41 Offline
Member

Registered: 03/07/05
Posts: 96
Loc: Lower Burrell, PA
Situation: detached garage with underground cable coming in no disconnect, just a junction box. It is fed from part of the unfinished basement lighting circuit which has armoured cable. It then goes into homeowners newly remodeled basement office which is finished with no access points to where the underground feed leaves the basement to the garage. The problem? Getting 121 volts across the neutral and bare ground wire in the garage and the exposed armoured cable in the basement I get 121 volt reading neutral to ground. The ground and the netrual is bonded together in the panel box. The armoured cable is clamped into the panel box properly. The rest of the circuits are new romex and properly grounded. What could be causing ground fault? Could inadequate grounding or bonding from the panel box allow this to happen? I would like to hear how others handled this problem? One thing I did notice and I used to different meters when checking to make sure, when I first touched my probes to get a reading, it quickly went to 240 something volts for a split second and then dropped down to 121v.

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#49788 - 03/17/05 08:56 AM Re: Hot Ground Question?
SJT Offline
Member

Registered: 07/24/02
Posts: 242
Loc: PATCHOGUE, N.Y.
The problem could be anywhere. Needs to be proprely trouble-shot. With out seeing the situation, it would be tough to run you through it step by step. It sounds like you have an open on the Hot-leg some where. The thing is, to find the problem, correct it, with out taking any short cuts.

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#49789 - 03/17/05 09:11 AM Re: Hot Ground Question?
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,

Did you just buy a new dmm?

FIRST READ THIS:
http://www.mikeholt.com/mojonewsarchive/...ts~20030409.htm
http://www.ecmweb.com/mag/electric_open_service_neutrals/


You could just be seeing the return voltage through a device..if you have a NON contact voltage tester handy you will probaly NOT see any voltage...if you are using a fluke then try a wiggy..this is common with dmm's..if this is the case there is not a problem..the meter is tricking you..some dmms will wrap around causing a false reading...use a simpson meter if you have one...dont use a fluke to test fuses in the circuit either...you can get false readings..indicating a good fuse when it is actually blown! always try and use an analog meter if you are in doubt they WONT lie most of the time..

if you have an outlet tester try using that it will tell you what is wrong..

when you make the connection between the neut and the ground you are completing the circuit and returning the unused power to the power co..in this case the neutral is OPEN...shut off the power and check continuity and see what you get...you must open both condcutors to do this...or you will read through the bond at the panel..

it sounds to me like you have a open nuetral or a backfeed or your meter is tricking you..

what type of service is it? 3 wire ? four wire? you MUST have three wire service to have a neutral...a neutral carries the unbalanced current..so nothin new by seeing voltage on a neutral..

Someone is/may be using the ground as a neutral somewhere on that service...

use caution when performing the next step...try to make sure there are no loads...use a amp probe..go turn off everthing you can...DO NOT OPEN THE NEUTRAL ON A LARGE LOAD!

shut off the MAIN...if you cant do that pull the meter...but do it without any loads..

go to the panel and remove each neutral from the bus...figure out which one is supplying the circuit you are working with...mark it...replace the others one by one AFTER you check your continuity between the questionable neutral and the ground...you will see which circuit is the prob..then trace it out and clear the ground that is tied to the neutral..chances are you will read through light bulbs and fluorescents etc..so watch out for that too..

if you find nothing..abandon that circuit and install a new one...that will solve it...remove that old circuit..sometimes this is quicker..

remove the grounds too and replace each one along with the corresponding neutral ONLY...do not get ahead of yourself...or you will get in a loop..

I hope you are a qualified person because if you are not I would not do this.

what you are describing is very common in situations where someone has done some creative wiring..

it is just a backfeed in simpler terms..

good luck and be careful..

-regards

greg



[This message has been edited by mustangelectric (edited 03-17-2005).]
_________________________
Electricity has no respect for ignorance!

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#49790 - 03/17/05 09:48 AM Re: Hot Ground Question?
JFLS41 Offline
Member

Registered: 03/07/05
Posts: 96
Loc: Lower Burrell, PA
Thanks for responding. I realized using the ground fault terminolgy was wrong after I posted the message.

I was finishing up work for this customer when I discovered this problem and didn't have the time to troubleshoot it. Plus the customer doesn't have anymore funds to pay me for additional work right now but will in the summer. The think the homeowner has bigger worries like broken garage door window glass hanging out of the frame by the putty. I mentioned this to him, especially since he has two boys running around and the hazard it is if it falls out. He did nothing.

As for the electrical problem. Perhaps it is backfeed or "loopback" but I think there is one of two possibilities here. 1. Someone used the existing wire in the underground feed which I think was only 2 conductor (I don't know exactly because it had a large gob of old sticky heat tape on it the size of a golfball)I didn't take the time to undo it and wire nut cause I knew the insulation would crumble and I would be rewiring that too. I basically told the customer this should be rewired given its age and condition. There is a possibility someone used the ground as a neutral from a light switch in the house or the hot wire insulation has broken down and is "leaking" into the ground, but not enough to trip the breaker. Like I said in my earlier post, the exit point where this underground feeder leaves the house is in a newly remodeled finished basement office.

On another note, being new to this residential work, if I tried to update or fix every corroded cable or replace the sticky black tape on these old jobs, I might as well re-wire the whole house. Of course I should sell that service but most of my work has been replacing fixtures, receptacles, etc...

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#49791 - 03/17/05 09:54 AM Re: Hot Ground Question?
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,
The term ground fault as you used it is ok..not a problem..as a matter of fact i removed my comment about that...after i chewed on it a little i realized that there is a possibility of a ground fault...

I see this all the time...nobody wants to pay for fixing something they dont realize is broke or understand..all you can do is pack up and leave..

you cant save the world!

troubleshooting is the hardest thing to sell as an electrician! you get very little for it in the end..unless you actually find it quick..

i have spent days looking for stuff and finally had to give up because not everything is accessible especially in finished construction..

just let them know that there is a dangerous situation lurking around..

good luck

-regards

greg
_________________________
Electricity has no respect for ignorance!

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#49792 - 03/17/05 10:13 AM Re: Hot Ground Question?
JFLS41 Offline
Member

Registered: 03/07/05
Posts: 96
Loc: Lower Burrell, PA
You made me think about something else in these situations. Lets say there is a dangerous situation lurking where a child or someone can get electrocuted or shocked. Say I am installing new lights, I do the work and leave. A kid grabs a junction box cover that has voltage on it. Goes crying to his mommy and first thing they say is, "we just had an electrician here, he must have done something wrong". They call their lawyer, etc etc... you how it works... what do you do when you get that call from them. How do you handle this. What has happened in the past?

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#49793 - 03/17/05 11:05 AM Re: Hot Ground Question?
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,
You have NO lIABILITY for ANY exisitng conditions or work performed or installed by others.

If you are aware of a dangerous situatuin I would at least notify the person in charge.

If they dont want you to fix it...they dont want you to fix it.

-regrds

greg
_________________________
Electricity has no respect for ignorance!

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#49794 - 03/17/05 11:41 AM Re: Hot Ground Question?
SJT Offline
Member

Registered: 07/24/02
Posts: 242
Loc: PATCHOGUE, N.Y.
Well said Mustang,
If you see something real bad, try to get it in writting, this way your protected in case things get crazy. In a sense, it could be extra work, and safer for the owner.

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#49795 - 03/17/05 12:13 PM Re: Hot Ground Question?
SJT Offline
Member

Registered: 07/24/02
Posts: 242
Loc: PATCHOGUE, N.Y.
Well said Mustang,
If you see something real bad, try to get it in writting, this way your protected in case things get crazy. In a sense, it could be extra work, and safer for the owner.

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#49796 - 03/17/05 07:08 PM Re: Hot Ground Question?
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
Hmmm... 121V n-g What is hot to ground?

What is, or isn't the circuit doing?

What are your phase voltages? Compare them to this.

Check against other known grounds, other EGC's or water pipe. One of these is not grounded, the ECG, or the "grounded conductor". (neutral)

What type of circuit is it 120 2-wire, or 120/240 3-wire? Are you sure? Shut everything off get your ohms between this neutral and ground (for referance), and check voltage as you turn on only one breaker at a time. You may have a double feed, or worse lost neutral on a 3-wire. (And it just happens to measure 121v, this will happen if the associated loads are near even.)

Now if the ground is really live, it is obviously not making a strong path back to the main. Some moron may have pulled the ground out, to avoid looking for the short they had no idea of how to find. If thats the case, ground it and go look for the short.

As for the jumpy meter, most DMM's are auto ranging, and will flash other voltages at first. And I have never had a DMM trick me, but I have tricked it, by tricking myself into thinking that was what I was really looking at. Wiggy's have tricked me!
_________________________
Mark Heller
"Well - I oughta....." -Jackie Gleason

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