# unusual voltage to ground



## RTM (Jul 26, 2011)

I was adding an outlet today at a local department store and we connected to a small bus duct that had 3 square d feed through breakers in an enclosure hooked to the bus duct. At the bottom of the enclosure were 3 pilot lights with 1 lead hooked to the line and the other hooked to the load on each breaker. Once we were done i checked the outlet for polarity and got a wierd reading so i checked with my wiggies and i had 120 to the neutral and 208 to ground. I went up to the enclosure and i got the same readings. Any thoughts as to why this is happening. There are other lights and outlets connected to another one of the breakers and they are working fine, didn't have time to ck. voltage on them


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## HARRY304E (Sep 15, 2010)

RTM said:


> I was adding an outlet today at a local department store and we connected to a small bus duct that had 3 square d feed through breakers in an enclosure hooked to the bus duct. At the bottom of the enclosure were 3 pilot lights with 1 lead hooked to the line and the other hooked to the load on each breaker. Once we were done i checked the outlet for polarity and got a wierd reading so i checked with my wiggies and i had 120 to the neutral and 208 to ground. I went up to the enclosure and i got the same readings. Any thoughts as to why this is happening. There are other lights and outlets connected to another one of the breakers and they are working fine, didn't have time to ck. voltage on them



Are you saying that you had 208 volts between neutral and ground?:blink:

Welcome to the forum.:thumbup::thumbup:


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## JohnR (Apr 12, 2010)

_Sounds_ like the department store used to be an old factory. Those pilot lights indicate which phase is connected to ground, or "shorted". That would be a floating ground system. Designed to keep production going till the fault can be found.


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## RTM (Jul 26, 2011)

HARRY304E said:


> Are you saying that you had 208 volts between neutral and ground?:blink:
> 
> Welcome to the forum.:thumbup::thumbup:


No, i only had 208 volts between the hot and the ground


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## RTM (Jul 26, 2011)

JohnR said:


> _Sounds_ like the department store used to be an old factory. Those pilot lights indicate which phase is connected to ground, or "shorted". That would be a floating ground system. Designed to keep production going till the fault can be found.


Explain what you mean by a floating ground system


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## JohnR (Apr 12, 2010)

As it was explained to me, the transformer neutral is not connected to ground anywhere. That way, if one leg or the neutral connects to ground, or faults, then you don't have a bang, just one of the lamps will come on, alerting the maintaince electrician to find the fault and restore it to original.

The way you described the lamps on the breaker, doesn't quite seem right to me, but I never did much in a factory. What I know comes from my tech teacher who worked in thread mills back in the day. Haven't see him in 17 years at least.

This method of floating the transformer isolated from ground, is the way hospital surgery power works. If one leg connects to the patient and causes a fault somehow, the max voltage the person could get would be 56 or so volts if memory serves. Not 120V which could kill them lying on a stainless table .


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## RTM (Jul 26, 2011)

JohnR said:


> As it was explained to me, the transformer neutral is not connected to ground anywhere. That way, if one leg or the neutral connects to ground, or faults, then you don't have a bang, just one of the lamps will come on, alerting the maintaince electrician to find the fault and restore it to original.
> 
> The way you described the lamps on the breaker, doesn't quite seem right to me, but I never did much in a factory. What I know comes from my tech teacher who worked in thread mills back in the day. Haven't see him in 17 years at least.
> 
> This method of floating the transformer isolated from ground, is the way hospital surgery power works. If one leg connects to the patient and causes a fault somehow, the max voltage the person could get would be 56 or so volts if memory serves. Not 120V which could kill them lying on a stainless table .


 
Thanks


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## MattMc (May 30, 2011)

Basically the system will run with one phase shorted to ground the light indicates which phase is shorted, untill you have time to find and fix the problem, if another phase shorts out your screwed though and have to clean up a bigger problem.


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## Big John (May 23, 2010)

RTM said:


> ...At the bottom of the enclosure were 3 pilot lights with 1 lead hooked to the line and the other hooked to the load on each breaker....


 _JohnR _is talking about ground-fault lights, but I've never seen a set connected the way you describe. They almost sound like phase-detection lights if you have an open pole, but I've also never seen those on breakers, only fuses.

-John


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## MattMc (May 30, 2011)

Usually if you have a short to ground you'll get wacky voltages like all 3 phases will be quite different I have only worked on 600v system like that instead of 347v on each phase all were different like 258v, 365v and 290v something weird like thatyet the whole plant still runs fine. I think I have got this right if the system you are discribing is what I think it is.


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## JohnR (Apr 12, 2010)

Just had another thought, it could be that the transformer IS connected to ground, and somehow the ground between the feed and your buss drop is broken somewhere. IF there is no building steel that is bonded all the way, It would theoretically be possible I suppose. '

What do you think of that idea?


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## Hippie (May 12, 2011)

It could also be that the transformer neutral isn't bonded at all, which would give 120 to neutral but something random to ground since they aren't actually connected. There's a transformer like that where I work, it isn't bonded and has 480 between phases but reads all different voltages to ground


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## MattMc (May 30, 2011)

That makes sense to me, because there shouldn't be that type of reading on a neutral ever. It's hard to say not being able to actually see this but I am interested in findout the conclusion to this.


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## sucocoop (Jun 23, 2010)

I'm no electrician by any means, but I do know a 4 wire delta from the distribution side provide 120 v from hot to neutral on two phases, 240 v from any hot to another hot, and 208 v from the wild leg to neutral. If you look inside the meter base, the 208 leg usually (and should be) the leg on the far right going through the meter. From there you can follow it after the CT's to see where the wild leg goes. This could possibly be no help to you. But I'm just a poor college student putting in my 1/2 cent.


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## brian john (Mar 11, 2007)

MattMc said:


> Usually if you have a short to ground you'll get wacky voltages like all 3 phases will be quite different I have only worked on 600v system like that instead of 347v on each phase all were different like 258v, 365v and 290v something weird like that yet the whole plant still runs fine. I think I have got this right if the system you are describing is what I think it is.


 
When the system is NOT grounded you would get weird voltages to ground. Once you ground any phase you get stable readings.


Whether it is a center tapped delat or a wye Neutral to ground 120 VAC, Phase to ground 208 VAC?

You have an improperly grounded wye or Delta. one phase SHOULDS be "0" VAC to ground.

On a wye, If one phase is grounded, (assume "A") then "A" to ground "0" VAC, "B" to ground 208 VAC, "C" to ground 208 VAC, Neutral to ground 120 VAC.

Some serious checking needs to be done


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## brian john (Mar 11, 2007)

sucocoop said:


> If you look inside the meter base, the 208 leg usually (and should be) the leg on the far right going through the meter. From there you can follow it after the CT's to see where the wild leg goes. This could possibly be no help to you. But I'm just a poor college student putting in my 1/2 cent.


 
The "high leg" can be in a variety of locations, different utilities do it differently. NEC has us move it to "B" Phase.


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## Jlarson (Jun 28, 2009)

Big John said:


> _...._They almost sound like phase-detection lights if you have an open pole...





Hippie said:


> It could also be that the transformer neutral isn't bonded at all....


If I'm understanding the OP correctly you guys are correct.


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## MattMc (May 30, 2011)

brian john said:


> When the system is NOT grounded you would get weird voltages to ground. Once you ground any phase you get stable readings.
> 
> 
> Whether it is a center tapped delat or a wye Neutral to ground 120 VAC, Phase to ground 208 VAC?
> ...


I was talking about leakage to ground, on a 600v system that I have seen before I wasn't resposible for fixing this problem, just installing some new equiptment on a line. The plant maintenance people had the responsability of fixing this leakage to ground. I am just using this as an example and the voltages I said were made up, but the readings were similar. To me it doesn't sound like the case in this post, also they are dealing with 208v, not 600v 3Phase. I was more or less refering to the use of phase detection system with the bulbs, for checking leakage to ground. I have seen them before, and like an earlier comment said they are usually in manufacturing facilities with much larger service and distribution equiptment than a department store would have.


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## brian john (Mar 11, 2007)

Matt,

When you have an ungrounded system, the voltage readings to ground are all over the place.

When that system is grounded accidently or intentionally the voltage to ground are to what ever conductor is grounded.


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## MattMc (May 30, 2011)

Thanks, I am here to learn new stuff and try and help when I can. Anything I see here or on the job that can make my trouble shooting skills better is good. I wasn't sure if maybe you had misinterperated what I had said that was all.


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## RIVETER (Sep 26, 2009)

In a properly installed "ungrounded" electrical system the system does not have an "intentionally" grounded "circuit" conductor. Are you guys saying that even in a properly installed "un"-grounded system that there will be these currents? There should not be.


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## MattMc (May 30, 2011)

No that's not what I was talking about.


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## Big John (May 23, 2010)

The part about getting exactly 208 to ground threw me, I didn't see that you'd measured it with a wiggy.

I agree it sounds like you have an ungrounded transformer. I bet if you put a digital meter L-G you would find some oddball voltage and not exactly 208.

-John


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## SteMo (Jul 10, 2011)

I had a sandwich oven today that was hooked up on a 30amp dryer recept. 1 leg to ground was 120v and 1 leg was 210v between was 240v. The nameplate said 208v/1ph. The owner said they had been hooked that way for 10 years


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## JohnJ0906 (Jan 22, 2007)

1stcallelectric said:


> I had a sandwich oven today that was hooked up on a 30amp dryer recept. 1 leg to ground was 120v and 1 leg was 210v between was 240v. The nameplate said 208v/1ph. The owner said they had been hooked that way for 10 years


240/120v High leg delta 3 phase.

2 hot legs will be 120v to ground/neutral, 1 leg (should be "B") will be approx. 208 to ground/neutral


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