is this right or wrong?

[electricalperson]

today i was doing a fire alarm system at a local hotel. the lady at the bar area called me over and asked me to look at her lights and plugs that didnt work. i took out my shiny new T+pro tester and stuck it in the receptacle and heres what i got.

L to N 119 volts

L to G 136 volts

N to G 45 volts

i called the "engineering" department and explained to them that they have a floating neutral and it should be fixed. (theres also receptacles in other parts of the buildings that dont work, not sure if its related or not and also a bunch of transformers for 120/208v 3 phase power to feed panels) but anyway they wouldnt let me fix the problem for some reason, but anyway was i correct with the term floating neutral? heres my guess on whats causing that (i didnt get to troubleshoot so its just a guess) XO on the transformer feeding the panel might not be grounded. anything wrong with that guess?

also the engineering department are not really engineers i think. they just fix stuff thats broken

[iwire]

heres my guess on whats causing that (i didnt get to troubleshoot so its just a guess) XO on the transformer feeding the panel might not be grounded.

IMO you are right, XO would be my first stop.

[electricalperson]

IMO you are right, XO would be my first stop.
thank you:D

[e57]

I usually make a pit stop on the way to the XO - at the panel feeding them. Usually easier to find, and saves you a lot of effort if it is only in a J-box right next to the outlet(s) in question. One of my rules of troubleshooting is to split the circuit in half - follow the bad half, and split it, etc - so on.....

Two things:

BTW it's not a situation to take lightly - Floating/lost neutrals (AKA 'High/low voltage event') can be very serious to the point where equipment or appliances are damaged and causes a fire. I'm sure there are many who have let the smoke out of things in this way.

And since your neutral and ground differ quite a bit - this may be a difficult find. As the ground may only be an ungrounded or partially hot from a boot-leg neutral someplace - either way a shock hazard at the bar. Did you check voltage from the ground of the outlet to say a sink plumbing fixture - or nearby appliances and such? I have seen a few situations where a neutral or even a hot can energize say a stainless counter top and act as a load - and in your situation from another phase... (As only the ground and not the neutral is showing a higher than nominal voltage.)

Both ways can be a fire or shock hazard.

[iwire]

I usually make a pit stop on the way to the XO - at the panel feeding them.

Why would you go to the panel first?


Usually easier to find, and saves you a lot of effort if it is only in a J-box right next to the outlet(s) in question.

How could this problem be in a j-box next to the outlets?

One of my rules of troubleshooting is to split the circuit in half - follow the bad half, and split it, etc - so on.....

That is not exactly your rule, that is basic common sense. :D

But the NEC requires the bonding jumper to be in either, or both, of two places. The transformer or the first disconnecting means. Because of the limited distances allowed for transformer secondaries if your at the first disconnecting means you should also be at the transformer.

BTW it's not a situation to take lightly - Floating/lost neutrals (AKA 'High/low voltage event')

Given the voltage readings this is without a doubt a bonding jumper issue.

L to N 119 volts

L to G 136 volts

N to G 45 volts

The L to N is 119 which pretty much rules out a lost neutral.

[e57]

Why would you go to the panel first?

Why would you assume that there only be an open between ground and grounded only at the transformer? Was everything in the whole area the transformer is serving affected?


How could this problem be in a j-box next to the outlets?

And open or resistive ground could be anywhere along the circuit.

That is not exactly your rule, that is basic common sense. :D

True - which is why I split things in half. :D While a bonding jumper could well be from what little either you or I see from this side of the screen as the issue - the possibility remains that it might not be.... So why start at the begining if there is the slightst possibility of ending up somewhere in the middle?

But the NEC requires the bonding jumper to be in either, or both, of two places. The transformer or the first disconnecting means. Because of the limited distances allowed for transformer secondaries if your at the first disconnecting means you should also be at the transformer.

And the panel right next to that, and this outlet right on the other side of the wall they are all on. ;)

Given the voltage readings this is without a doubt a bonding jumper issue.

It could be an intentional or un-intentional boot-leg neutral from another ciircuit IMO? It could be an open ground and the infamous 'ghost voltage' - as mentioned many times I do not beleive in ghosts... But since it is higher than nominal hot to ground and the math adds up for neutral to ground - I would think energized from another phase. It could be a lot of things IMO. :-? It could be you're right?

The L to N is 119 which pretty much rules out a lost neutral.

One would tend to think so - but since I'm on this side of my monitor, and and only know about readings taken at a single outlet near a bar - why rule anything out. :rolleyes:

Anyway, I think half both the discovery phase of troubleshooting, and learning begins with following a logical process. I think you get what I mean right?:rolleyes:

[e57]

the lady at the bar area called me over and asked me to look at her lights and plugs that didnt work.

So what was wrong with them? Sounds like the oulet in question would have worked fine - outside of being a potential hazard.

[Lxnxjxhx]

Dear E. Person:

So that I can follow along, can you tell me which of the configurations in the site below you are using? I'd like to do the whole analysis, etc., with unbalanced loads and so on, to see if I can get your voltages.
Thanks.

http://insayne_kokane.tripod.com/transformers.shtml

Regards,

H. Person

[iwire]

Anyway, I think half both the discovery phase of troubleshooting, and learning begins with following a logical process. I think you get what I mean right?:rolleyes:

Yes, and IMO given the conditions I would go to XO / first disconnect first.
I would not try to figure out where half way was until I determined each end.

To each their own.

[electricalperson]

Dear E. Person:

So that I can follow along, can you tell me which of the configurations in the site below you are using? I'd like to do the whole analysis, etc., with unbalanced loads and so on, to see if I can get your voltages.
Thanks.

http://insayne_kokane.tripod.com/transformers.shtml

Regards,

H. Person
im pretty sure the transformer was a 480/277 delta primary to a 120/208 volt wye secondary. like i said i didnt troubleshoot anything since they wouldnt let me for some reason. i think the maintanence department likes to play electrician

[electricalperson]

So what was wrong with them? Sounds like the oulet in question would have worked fine - outside of being a potential hazard.
if theres a floating neutral it wouldnt work. her appliances didnt work in any of the outlets she told me and none of the lights didnt work. like i said all i did was do a quick test on a receptacle that she was using and noticed the weird voltages. im assuming its a floating neutral because of what the meter said. she had a power strip that had a light on the button and the light was very faint when it was turned on

[Buck Parrish]

today i was doing a fire alarm system at a local hotel. the lady at the bar area called me over and asked me to look at her lights and plugs that didnt work. i took out my shiny new T+pro tester and stuck it in the receptacle and heres what i got.

L to N 119 volts

L to G 136 volts

N to G 45 volts

i called the "engineering" department and explained to them that they have a floating neutral and it should be fixed. (theres also receptacles in other parts of the buildings that dont work, not sure if its related or not and also a bunch of transformers for 120/208v 3 phase power to feed panels) but anyway they wouldnt let me fix the problem for some reason, but anyway was i correct with the term floating neutral? heres my guess on whats causing that (i didnt get to troubleshoot so its just a guess) XO on the transformer feeding the panel might not be grounded. anything wrong with that guess?

also the engineering department are not really engineers i think. they just fix stuff thats broken



I would have told her after that reading I got. I would need a drink in order to think about it.

[crossman]

The OP said the receptacles didn't work, but still measured 119v from L to N. This does not sound like a missing SBJ at the XO terminal. Sounds to me like a bad neutral connection somewhere between the xfmr and the receptacle. As someone mentioned, the 119v was an ohm's law reaction to a high impedance meter and a relatively lower impedance in series with the neutral.

[electricalperson]

if the neutral was grounded, the voltage would be stable. no ground on the neutral makes funny stuff happen sometimes. theres also a bunch of receptacles in the kitchen area that dont work either.

[iwire]

How could this problem be in a j-box next to the outlets?

And open or resistive ground could be anywhere along the circuit.

No, that condition alone can not result in these measurements.

L to N 119 volts

L to G 136 volts

N to G 45 volts

I don't care how resistive the EGC is, it will not result in a N to G voltage of 45 volts. (Not by itself, perhaps with a second fault as well)


Why would you assume that there only be an open between ground and grounded only at the transformer?

Because they should be open every but there, and if they where connected the potential between them would be much less then 45 volts.

[electricalperson]

The OP said the receptacles didn't work, but still measured 119v from L to N. This does not sound like a missing SBJ at the XO terminal. Sounds to me like a bad neutral connection somewhere between the xfmr and the receptacle. As someone mentioned, the 119v was an ohm's law reaction to a high impedance meter and a relatively lower impedance in series with the neutral.
thats also possible. nothing was taken apart and no troubleshooting done, just a quick test with the t+pro

[crossman]

If there was a poor neutral connection somewhere between X0 and the receptacle, the portion of the neutral connected to the receptacle would not be at ground potential.

Why would a missing system bonding jumper at X0 cause the receptacles not to work even though there was a measured 119v there?

[iwire]

Why would a missing system bonding jumper at X0 cause the receptacles not to work even though there was a measured 119v there?


(theres also receptacles in other parts of the buildings that dont work, not sure if its related or not

I am assuming that it is unrelated.

[electricalperson]

I am assuming that it is unrelated.
i wish they would let me troubleshoot it instead of looking in the other direction.

[crossman]

Hmmm.... I can see we could get the 119v LN and the 45v NG but to get the 135 LG then there does need to be another poor or missing connection somewhere I think.

http://i173.photobucket.com/albums/w70/garygauge/neut.jpg

[Lxnxjxhx]

Thanks for the info.

"i think the maintanence department likes to play electrician"
Fine, let'em fix it. They can have the credit as long as they take the risks.

[e57]

Quote:
(theres also receptacles in other parts of the buildings that dont work, not sure if its related or not

I am assuming that it is unrelated.We (including the OP) can not really assume anything.

But IMO If all the voltages that we have - which are not all of them - were taken in a single snap shot on this wye system would mean that this 'floating' neutral is floating someplace between the other two phases...

was taken apart and no troubleshooting done, just a quick test with the t+pro



Just looked up this T+pro (http://us.fluke.com/usen/products/features.htm?cs_id=37115(FlukeProducts)&category=ELT(FlukeProducts)) thing.... Not heard of one before - I'm going to deam it the "Wigi-roto-vo-meter", because it looks and acts like a 'wiggy' style solonoid, has rotation indication and a digital AC/DC volt/ohm meter. Apparently tests GFCI's as well????

[electricalperson]

We (including the OP) can not really assume anything.

But IMO If all the voltages that we have - which are not all of them - were taken in a single snap shot on this wye system would mean that this 'floating' neutral is floating someplace between the other two phases...



Just looked up this T+pro (http://us.fluke.com/usen/products/features.htm?cs_id=37115(FlukeProducts)&category=ELT(FlukeProducts)) thing.... Not heard of one before - I'm going to deam it the "Wigi-roto-vo-meter", because it looks and acts like a 'wiggy' style solonoid, has rotation indication and a digital AC/DC volt/ohm meter. Apparently tests GFCI's as well????
yea they claim is safer than an old solenoid tester. i like it a lot since it has an LCD screen that shows the voltage as well

[iwire]

We (including the OP) can not really assume anything.

But IMO If all the voltages that we have - which are not all of them - were taken in a single snap shot on this wye system would mean that this 'floating' neutral is floating someplace between the other two phases...

Even if it is a 'snap shot' given the voltage mesuments it can not be a 'lost' neutral, it is a neutral that is not bonded to the grounding system.

Look at Carl's drawing. :smile:

[e57]

Bob I'm not saying it is or isn't - we don't know is what I have been saying.

Is Carls drawing this one? The one woth the bonded XO.


http://i173.photobucket.com/albums/w70/garygauge/neut.jpg

[jerm]

Bob I'm not saying it is or isn't - we don't know is what I have been saying.

Is Carls drawing this one? The one woth the bonded XO.


http://i173.photobucket.com/albums/w70/garygauge/neut.jpg

That looks like the things I used to draw on my TabletPC before it bit the dust. So was it a TabletPC something else? Not mouse work IMHO... just curious

[e57]

What if?

A=75, B=166, and C=119

We don't know.

Other outlets in the building are not working, and this one tested at 119 apparently was not.

All I'm trying to say is not to rule anything out - and since we'll never find out - whats the point? :rolleyes:

[electricalperson]

What if?

A=75, B=166, and C=119

We don't know.

Other outlets in the building are not working, and this one tested at 119 apparently was not.

All I'm trying to say is not to rule anything out - and since we'll never find out - whats the point? :rolleyes:
im going to try to work on the maintanence people to let us do the work

[Lxnxjxhx]

I realized I could hardly solve a 2 phase problem.

Does everyone agree that a 10 volt source in series with a 1 ohm resistor in series with an opposing 8 volt source gives a current of 2 amps in the resistor?

If so, if the 10 volt source is at an angle of zero degrees and the 8 volt source is at an angle of +90 degrees, does everyone agree that, according to the rules of working with complex numbers, the current through the resistor is now 12.8 amps at an angle of -39.7 degrees?

The trick is that subtracting two vectors A and B, where A is c + jd and B is e + jf, is equal to = (c-e) + j(d-f).

For A, the 10 volt source, c = 10 and d = 0
For B, the 8 volt source, e = 0 and f = 8

The 3 phase problem, still in progress, is more of the same, a lot more.

[George Stolz]

That is not exactly your rule, that is basic common sense. :D

I was told firmly last week to start at the end and work backwards. I giggled and said I was going to start in the middle. :)

[quogueelectric]

But the NEC requires the bonding jumper to be in either, or both, of two places. The transformer or the first disconnecting means. Because of the limited distances allowed for transformer secondaries if your at the first disconnecting means you should also be at the transformer
I was under the impression that it had to be one or the other but not both.

[iwire]

I was under the impression that it had to be one or the other but not both.

It can be both if it does not establish a parallel path between them.

250.30(A)(1) Exception 2

[iwire]

Bob I'm not saying it is or isn't - we don't know is what I have been saying.

Mark we will have to agree to disagree here. :smile:

IMO given those readings it has to be lack of system bonding. It can not just be a lost neutral.

But I do undestand we are not there and we did not take the mesurments. :smile:

[jrannis]

20 years ago or so, I went to a service call at a bar where they were getting shocked from the sink.
The maintenance man installed a ground rod under the stainless steel sink and connected them with a water pipe ground clamp.
My job was to reconnect the clamp that had somehow been knocked off.
This was before GFIs were required for this type of installation I think.
They didnt have a transformer but they also didnt have the neutral and ground connected at the service. I corrected it.
I hammered the ground rod through the slab and patched the hole.
No more shocks from the sink.

[quogueelectric]

It can be both if it does not establish a parallel path between them.

250.30(A)(1) Exception 2
How could it possibly not establish a parallel path between them?? This would be impossible in my opinion.

[iwire]

How could it possibly not establish a parallel path between them?? This would be impossible in my opinion.

Use non-metallic raceways or cable between them.

I did not write the rule and I do not know why it's there.

[quogueelectric]

Use non-metallic raceways or cable between them.

I did not write the rule and I do not know why it's there.
I am not trying to be a wiseguy (Imagine that) but how would this not cause a ground loop just what they are trying to eliminate?? I dont get it. This is wrong and needs to be addressed in my opinion.

[iwire]

I am not trying to be a wiseguy (Imagine that) but how would this not cause a ground loop just what they are trying to eliminate?? I dont get it. This is wrong and needs to be addressed in my opinion.

There will be no 'loop' if you use non-metallic raceways, the only path will be the grounded conductor. :smile:

I have never seen the need for this but I have not seen everything.

[76nemo]

The OP said the receptacles didn't work, but still measured 119v from L to N. This does not sound like a missing SBJ at the XO terminal. Sounds to me like a bad neutral connection somewhere between the xfmr and the receptacle. As someone mentioned, the 119v was an ohm's law reaction to a high impedance meter and a relatively lower impedance in series with the neutral.

Flukes T+ does not have high impedance input.

[quogueelectric]

There will be no 'loop' if you use non-metallic raceways, the only path will be the grounded conductor. :smile:

I have never seen the need for this but I have not seen everything.
Even if you could use pvc in the building which you cant due to fire code .(They allow it for the pool feeder by me) if you ground the neutral in two different locations you definitely have a ground loop. It is in fact the definition of a ground loop. The neutral should only be bonded at 1 point or else you have a ground loop.

[quogueelectric]

Flukes T+ does not have high impedance input.
They play cute by only limiting thier ohms scale to 400 ohms the it reads ol out of limits so you cant use it as a dvm and have to buy a second meter to read ohms. I think they could do better.

[76nemo]

They play cute by only limiting thier ohms scale to 400 ohms the it reads ol out of limits so you cant use it as a dvm and have to buy a second meter to read ohms. I think they could do better.

I agree q., but with a low-Z input, phase rotation indication, an LCD readout, GFCI testing, LED light, and a CATIII rating for 600V's, it's very hard to complain. What I have always said about the T+ that I didn't like was the vibration indication. When I am working on a large enough service, the last thing I want is some meter/tester vibrating in my hand. The vibration is not switchable.

Hey, for $85, it's not a bad deal;)

[crossman]

if you ground the neutral in two different locations you definitely have a ground loop. It is in fact the definition of a ground loop. The neutral should only be bonded at 1 point or else you have a ground loop.

Here is a diagram of where the double bonding would be allowed.

2008 NEC 250.30(A)(1) Ex 2 allows two SBJs where no parallel path is created

2008 NEC 250.142(A)(3) allows the grounded conductor to be used to bond/ground equipment, in other words, the grounded conductor functions as both the neutral and the equipment grounding conductor in this instance.

http://i173.photobucket.com/albums/w70/garygauge/0011.jpg

[iwire]

Carl I have been thinking on this and in your diagram I think we will have a parallel path through the un-shown EGCs in most cases. (Steel building, the GEC required by 250.30(A)(3) etc.)

I was thinking an application of this rule would be a facility that distributes power at high voltage around their property and then has pad mounts at each service.

Typically you would bond at the pad mount and at the feeder entrance disconnect.

[crossman]

Bob, I assume you are addressing me. I don't see where any EGCs are causing parallel paths. This is an all wood structure.... no building steel, no water pipe, only a driven ground.

[crossman]

I started a new thread for my topic of two bonds on the neutral. Please reply in the following thread if interested.

http://forums.mikeholt.com/showthread.php?p=838922#post838922post838922