is this right or wrong?

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Lxnxjxhx

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480/277 delta primary to a 120/208 volt wye secondary

480/277 delta primary to a 120/208 volt wye secondary

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

Senior Member
iwire said:
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...

electricalperson said:
was taken apart and no troubleshooting done, just a quick test with the t+pro
Just looked up this T+pro 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

Senior Member
e57 said:
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 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

Moderator
Staff member
e57 said:
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

Senior Member
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.


 

jerm

Senior Member
e57 said:
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.


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

Senior Member
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

Senior Member
e57 said:
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
 
L

Lxnxjxhx

Guest
While trying to solve a 3 phase problem. . .

While trying to solve a 3 phase problem. . .

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

Moderator
Staff member
iwire said:
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

Senior Member
iwire said:
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

Moderator
Staff member
quogueelectric said:
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

Moderator
Staff member
e57 said:
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:
 
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jrannis

Senior Member
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

Senior Member
iwire said:
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

Moderator
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quogueelectric said:
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

Senior Member
iwire said:
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

Moderator
Staff member
quogueelectric said:
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

Senior Member
crossman said:
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

Senior Member
iwire said:
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.
 
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