# 13V Between Neutral and Ground at a Grocery Store



## Bad Electrician (May 20, 2014)

Where are you measuring the 13 VAC?

What is the phase to neutral voltage
What is the phase to ground voltage


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## ponyboy (Nov 18, 2012)

Harmonics can do that. What are loads?


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## CFL (Jan 28, 2009)

That grocery store probably uses a ct meter. The service conductors don't actually connect to it and pass current through it. Are you familiar with that?


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## swimmer (Mar 19, 2011)

CFL said:


> That grocery store probably uses a ct meter. The service conductors don't actually connect to it and pass current through it. Are you familiar with that?


No, but it sounds like the current clamp on my meter.


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## swimmer (Mar 19, 2011)

Bad Electrician said:


> Where are you measuring the 13 VAC?
> 
> What is the phase to neutral voltage
> What is the phase to ground voltage



13 VAC is between neutral and ground in the switch equipment about 1 foot down stream from the transformer. 

Phase to neutral is approx 121V on all 3 phases
Phase to ground is:
BLK: 124V
RED: 110V
BLU 130V


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## swimmer (Mar 19, 2011)

ponyboy said:


> Harmonics can do that. What are loads?


I'm not sure about the loads. Computerized cash registers, a DVD dispenser and fluorescent lights are a few of them.

I'm working on the DVD dispenser. It gets a high phase to ground voltage at night. Sometimes as high as 140V. I've got it connected phase to neutral tonight.


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## Bad Electrician (May 20, 2014)

ponyboy said:


> Harmonics can do that. What are loads?


Substantiation please


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## Bad Electrician (May 20, 2014)

swimmer said:


> 13 VAC is between neutral and ground in the switch equipment about 1 foot down stream from the transformer.
> 
> Phase to neutral is approx 121V on all 3 phases
> Phase to ground is:
> ...


MY GUESS - Screw the harmonics (why chase ghost), the system appears to have a neutral to ground bond issue.


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## swimmer (Mar 19, 2011)

Bad Electrician said:


> MY GUESS - Screw the harmonics (why chase ghost), the system appears to have a neutral to ground bond issue.


The connection should be in the transformer housing as shown in my top picture right?

I don't think a modern grocery store would be wired as shown in the bottom picture.


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## retiredsparktech (Mar 8, 2011)

Bad Electrician said:


> MY GUESS - Screw the harmonics (why chase ghost), the system appears to have a neutral to ground bond issue.


Once in a while, you have to go back to the old Simpson 260, when tracing a problem like this. 
Any installation like this, that has discharge lighting, switching power supplies and all the rest of the high tech equipment, all the circuits will be rich in harmonics.
Some places, where they switched to electronic ballasts, it's even almost impossible to get FM reception, where before it was almost immune to electrical interference.


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## Bad Electrician (May 20, 2014)

swimmer said:


> The connection should be in the transformer housing as shown in my top picture right?
> 
> I don't think a modern grocery store would be wired as shown in the bottom picture.


Could be either way.

What I would do, I'd shut off the loads, install a temporary jumper, turn on the loads and measure the Neutral to ground voltage.

How far from the panel to the transformer?

The other issue would be voltage drop but that would require a long distance, under sized conductors and possibly a bad connection in the transformer?


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## Bad Electrician (May 20, 2014)

retiredsparktech said:


> Once in a while, you have to go back to the old Simpson 260, when tracing a problem like this.
> Any installation like this, that has discharge lighting, switching power supplies and all the rest of the high tech equipment, all the circuits will be rich in harmonics.
> Some places, where they switched to electronic ballasts, it's even almost impossible to get FM reception, where before it was almost immune to electrical interference.


I'd be highly surprised and eating my hat if this were the case. But I have been wrong many times. Never rule anything out.


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## Big John (May 23, 2010)

swimmer said:


> ...Phase to neutral is approx 121V on all 3 phases
> Phase to ground is:
> BLK: 124V
> RED: 110V
> BLU 130V


 That's a lot more phase imbalance than I would want to see.

What's the current on each phase?

I almost wonder if you're completely ungrounded.


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## swimmer (Mar 19, 2011)

Bad Electrician said:


> How far from the panel to the transformer?


I'm pretty sure the service panel meter is outside and below the transformer. Maybe 15 feet max. The transformer is on a 2nd story atrium in the back of the store. The switch gear where I measure the 13V between gnd and neutral is 1 foot down stream from the transformer. The circuit beaker panels that feed the loads are 150 feet away from the transformer at the other end of the store. I see the same 13V there.


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## Bad Electrician (May 20, 2014)

swimmer said:


> I'm pretty sure the service panel meter is outside and below the transformer. Maybe 15 feet max. The transformer is on a 2nd story atrium in the back of the store. The switch gear where I measure the 13V between gnd and neutral is 1 foot down stream from the transformer. The circuit beaker panels that feed the loads are 150 feet away from the transformer at the other end of the store. I see the same 13V there.


See Big John's post above and do what I posted.

No way in heck is this harmonics.


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## swimmer (Mar 19, 2011)

Big John said:


> That's a lot more phase imbalance than I would want to see.
> 
> What's the current on each phase?
> 
> I almost wonder if you're completely ungrounded.


I mixed up BLK and BLU voltages previously


Voltage to GND: BLK 130V, RED 111V, BLU 125V, WHT 13V

Voltage to Neutral: BLK 123V, RED 122V, BLU 121V, WHT 0V

Current: BLK 3.0A, RED 4.8A, BLU 4.8A, WHT 4.0A


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## Big John (May 23, 2010)

Silly question, what happens when you try for continuity ground to neutral? I agree with your first post, I think the bonding jumper is missing.


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## swimmer (Mar 19, 2011)

Big John said:


> Silly question, what happens when you try for continuity ground to neutral? I agree with your first post, I think the bonding jumper is missing.


I did it with power on at breaker panels that serve the loads. These panels are 150 feet from the 150kVA 480 - 208 transformer. Sometimes I got a few ohms and sometimes I got open circuit. I think its an invalid measurement with power on.

This 13V does not seem to be affecting the grocery store. I don't even know if it is affecting the DVD dispenser I'm working on. It does create confusion and I have safety concerns. I'm concerned about disrupting store operation so I haven't cut power to the store, or a big chunk of it, to properly ohm the GND to Neutral connection.


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## Bad Electrician (May 20, 2014)

swimmer said:


> I did it with power on at breaker panels that serve the loads. These panels are 150 feet from the 150kVA 480 - 208 transformer. Sometimes I got a few ohms and sometimes I got open circuit. I think its an invalid measurement with power on.
> 
> This 13V does not seem to be affecting the grocery store. I don't even know if it is affecting the DVD dispenser I'm working on. It does create confusion and I have safety concerns. I'm concerned about disrupting store operation so I haven't cut power to the store, or a big chunk of it, to properly ohm the GND to Neutral connection.


As noted several times neutral to ground bond.

The store equipment could care less if there is a ground.


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## don_resqcapt19 (Jul 18, 2010)

Big John said:


> That's a lot more phase imbalance than I would want to see.
> 
> What's the current on each phase?
> 
> I almost wonder if you're completely ungrounded.


Not really phase imbalance...he says the phase to neutral voltage is 121 on all phase.
I think you are correct...there is no system bonding jumper.


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## CFL (Jan 28, 2009)

Bad Electrician said:


> As noted several times neutral to ground bond.
> 
> The store equipment could care less if there is a ground.


Not exactly true. A surge suppressor will care. 

I also agree with the neutral/ground bond.


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## Meadow (Jan 14, 2011)

My monies on big John.


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## Bad Electrician (May 20, 2014)

Let us know.


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## swimmer (Mar 19, 2011)

Installed a system bonding jumper in the switch gear cabinet which is about 20 inches downstream from the 150KVA 480V delta to 208V wye transformer. The 13V went away. I have about 400mA in the jumper. Not sure if my clamp on meter even resolves that low. Thanks for the help. Good thing there were no ground faults in the parts of the store served by this equipment in the 10 years or so since this equipment was installed.


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## swimmer (Mar 19, 2011)

CFL said:


> Not exactly true. A surge suppressor will care.
> 
> I also agree with the neutral/ground bond.


2 suppressors fried during this episode. Thanks for the info.


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## CFL (Jan 28, 2009)

swimmer said:


> Installed a system bonding jumper in the switch gear cabinet which is about 20 inches downstream from the 150KVA 480V delta to 208V wye transformer. The 13V went away. I have about 400mA in the jumper. Not sure if my clamp on meter even resolves that low. Thanks for the help. Good thing there were no ground faults in the parts of the store served by this equipment in the 10 years or so since this equipment was installed.


So you put a bonding jumper in the 480 gear on the primary side of the transformer? I thought you had a 208/120 issue?


edit: sorry, i see now it says downstream. When I saw switch gear I thought 480, but I see what you're saying.


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## CFL (Jan 28, 2009)

Good job, by the way.:thumbsup:


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## Bad Electrician (May 20, 2014)

swimmer said:


> Installed a system bonding jumper in the switch gear cabinet which is about 20 inches downstream from the 150KVA 480V delta to 208V wye transformer. The 13V went away. I have about 400mA in the jumper. Not sure if my clamp on meter even resolves that low. Thanks for the help. Good thing there were no ground faults in the parts of the store served by this equipment in the 10 years or so since this equipment was installed.


A ground fault would have given them a grounded system be it A, B or C phase. I have seen this several times. While a NEC violation and it is not a distribution system one should operate with. It has been done accidently more than once. Then there are corner grounded deltas.


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## power (Feb 27, 2012)

Here is what I would do: Open up the switchgear and temporarily hand-hold a jumper from ground to neutral, then get your helper to check for the 13volt problem somewhere upstream. Does the problem remain? If so, "Bad Electrician" is correct.....you've a neutral that's not grounded. 

NOTE: In Canada, we call it "nailing down the starpoint". When we've a 3-phase/4-wire wye (Y) secondary service, we must ground the "starpoint" of the wye, or figuratively _nail_ it earth. If this is not accomplished, the phase voltages can "float" depending on the resistance and impedance connected to that respective phase. When that happens, you'll get readings very similar to what your experiencing......130, 125, 111. Grounding the star-point of any wye system will be a mandated US code as well.


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## A Little Short (Nov 11, 2010)

power said:


> Here is what I would do: Open up the switchgear and temporarily hand-hold a jumper from ground to neutral, then get your helper to check for the 13volt problem somewhere upstream. Does the problem remain? If so, "Bad Electrician" is correct.....you've a neutral that's not grounded.
> 
> NOTE: In Canada, we call it "nailing down the starpoint". When we've a 3-phase/4-wire wye (Y) secondary service, we must ground the "starpoint" of the wye, or figuratively _nail_ it earth. If this is not accomplished, the phase voltages can "float" depending on the resistance and impedance connected to that respective phase. When that happens, you'll get readings very similar to what your experiencing......130, 125, 111. Grounding the star-point of any wye system will be a mandated US code as well.


You're about a month late, the OP already said he done this:



swimmer said:


> Installed a system bonding jumper in the switch gear cabinet which is about 20 inches downstream from the 150KVA 480V delta to 208V wye transformer. The 13V went away. I have about 400mA in the jumper. Not sure if my clamp on meter even resolves that low. Thanks for the help. Good thing there were no ground faults in the parts of the store served by this equipment in the 10 years or so since this equipment was installed.


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## power (Feb 27, 2012)

I see that now. I am not too experienced with these types of "commenting" websites. I didn't see there was a second page, so all I read was the comments one page 1 (of two). Whoops!


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## swimmer (Mar 19, 2011)

power said:


> I see that now. I am not too experienced with these types of "commenting" websites. I didn't see there was a second page, so all I read was the comments one page 1 (of two). Whoops!



Thanks anyway for the information. Always good to how other electricians deal with or interpret the symptoms I run into.


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## Bad Electrician (May 20, 2014)

power said:


> I see that now. I am not too experienced with these types of "commenting" websites. I didn't see there was a second page, so all I read was the comments one page 1 (of two). Whoops!


I have posted a heck of a lot worse do not let that deter you from the posting.:thumbsup:


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## Meadow (Jan 14, 2011)

power said:


> I see that now. I am not too experienced with these types of "commenting" websites. I didn't see there was a second page, so all I read was the comments one page 1 (of two). Whoops!


Neither am I. Im still figuring out how to use this electrical Myspacebook talk forum. :laughing: :jester:


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## A Little Short (Nov 11, 2010)

A Little Short said:


> You're about a month late, the OP already said he done this:





power said:


> I see that now. I am not too experienced with these types of "commenting" websites. I didn't see there was a second page, so all I read was the comments one page 1 (of two). Whoops!


I wasn't "spanking" you, I was just kidding. Should have put a "smiley" or something!:jester:

I've also done worse, I've had a page loaded for a while thinking or typing a reply. By the time I finally hit "post" there have been umpteen posts, negating what I just typed.

Most common thing I see (and just maybe I have done it) is posting to a 5 year old thread!


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## Meadow (Jan 14, 2011)

A Little Short said:


> I wasn't "spanking" you, I was just kidding. Should have put a "smiley" or something!:jester:
> 
> I've also done worse, I've had a page loaded for a while thinking or typing a reply. By the time I finally hit "post" there have been umpteen posts, negating what I just typed.
> 
> Most common thing I see (and just maybe I have done it) is posting to a 5 year old thread!


:laughing: I did that once by mistake, came up searching a thread for a code reference. Thought it was within a few days turned out 5 years at least:laughing:


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## power (Feb 27, 2012)

Hey, it's all good! :thumbup: 

I just figured out where to use these "smile faces". Whenever I replied before, I used the "QUICK REPLY" box at the bottom of the page, but never noticed any "smile faces" to choose from. I guess you have to click "POST REPLY" to get more options in your message transmission, such as "smile faces", "grump faces", "shocked faces", "puzzled faces", ha!


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