Strange AC Power Issue

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francesco
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Post by francesco » Wed Aug 08, 2007 10:27 pm

Well here we go. These are the results:

hot+cold water pipe= 119V
neutral+cold water pipe= 0V
ground+cold water pipe= 27V

I tested neutral+metal at the panel and came up with 27V. When I put the volt meter between hot and ground on the same circuit as my UPSs they beep and click constantly. When I use the outlet tester they beep for 1 second.

I think I have to get maintanence to look at this because I just don't want to get into a situation where they say I did something. And I'm thinking the problem is probably in the panel or at the main of the building.

All the outlets here are 3 prongs. I checked a couple of the outlets and they have the proper ground. I haven't checked with my neighbors yet.

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Chris Smith
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Post by Chris Smith » Wed Aug 08, 2007 10:38 pm

You have a definite neutral / ground problem.

Robert Reed
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Post by Robert Reed » Thu Aug 09, 2007 12:23 am

Fransesco
From your tests concerning the panel, yes it is definately time to drop the ball and call in an electrician, especially since this is apartment complex proprerty.
Chris Smith
Go back and read my reply carefully . Every word is simplistic truth and cannot be denied. Your post is hard to understand and has flaws in it. Do you really know the inter workings of GFI circuitry? If you did, you wouldn't keep referring to ground currents as being sensed by it. You do not even need a ground to trip these. They work strictly on differential currents thru a differential transformer on their input which only sees the black and white wire currents. It does not even see any ground wire current. When this differential current exceeds 5 milliamps the circuit trips- it's as simple as that. As far as me needing to bone up, I beleive I have covered the topic quite thoroughly. Your ideas have not only defeated the purpose of the safety ground but have set the NEC back 60 years.

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jwax
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Post by jwax » Thu Aug 09, 2007 3:33 am

To add another twist, francesco- Are you using a digital voltmeter, or an analog meter? A digital meter could read "different" than an analog meter, giving false results.

francesco
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Post by francesco » Thu Aug 09, 2007 4:46 am

jwax wrote:To add another twist, francesco- Are you using a digital voltmeter, or an analog meter? A digital meter could read "different" than an analog meter, giving false results.
Yes I am using a digital one. But with all the other facts can it really be a false result?

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jwax
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Post by jwax » Thu Aug 09, 2007 8:22 am

Call me curious- digitals can be fooled. If you can, repeat the measurements with an old analog meter.

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jollyrgr
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Post by jollyrgr » Thu Aug 09, 2007 8:33 am

francesco

Whatever the outcome, please post an answer as I'm very interested in this problem now.
No trees were harmed in the creation of this message. But billions of electrons, photons, and electromagnetic waves were terribly inconvenienced!

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haklesup
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Post by haklesup » Thu Aug 09, 2007 10:41 am

If you've already unplugged everything with a ground prong on the power cord and its still there, I'd have to agree, it's in the building wiring.

In any case, be aware that any appliance you do have plugged in that has a ground prong may have its case charged to 25V. If you touch it and the water pipe, there is a risk of a shock. It's hard to asses the risk because I don't know how much current is available.

francesco
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Post by francesco » Thu Aug 09, 2007 8:55 pm

I shut off all the breakers in the panel and getting 2V between ground and neutral.

I have a feeling it's a problem in the whole building. I have to check with the neighbor.

John: unfortunately I threw the analog ones out a few months ago. I had 2 cheap ones that I bought in 1989 :)

I called the rental office today and they got on the issue immediately. NOT! They probably won't look at it until Monday.

b1miller
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Post by b1miller » Thu Aug 09, 2007 9:14 pm

Robert,
Excellent post regarding GFCI operation. One of the common uses of a GFCI outlet is when updating older house wiring that used 2 conductor wiring without a ground wire. The NEC allows the use of a GFCI outlet to replace an existing ungrounded outlet which then also protects any downstream outlets. Also a good point regarding the difference between the grounded conductor and the grounding conductor.

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Chris Smith
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Post by Chris Smith » Thu Aug 09, 2007 9:15 pm

Robert, Grounds and neutrals are exactly the same thing, depending only on wiring.

The only difference is one is set aside for safety, the other carries the power, both end up exactly at the same place.

To add in more EARTH grounds is perfectly safe, even adding a jumper between the neutral plug and these grounds. Sending a return power to the neutral or a ACTUAL ground is perfectly safe, especially if both are used, like every house already does.

The only thing it screws up is the GFI sensitivity.

Thevenin circuits show how you can have a parallel round trip, one carrying a current, the second one as a sense circuit. To power a Ground simply means you have no safety, and it was designed in case of failure, not meant for every day work.

The average ground carries no current so that it is a by pass or safety shoulder, then able to react when trouble arises. Under normal circumstances it carries no current for the purpose of carrying a current, if the safety or need arises.

The neutral goes back to the panel, then connects with the power company neutral, but long before it dose this it also goes to ground at least once, perhaps twice depending on your configuration. If it’s a mobile home then by law, it needs a third chassis ground as well.

All grounds and neutrals are one, and the only difference between them is length, size, and distance.

As To GFI, there are more than one types, most using the ground as a “DEADâ€

Oxford
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Post by Oxford » Fri Aug 10, 2007 10:43 am

I have seen an industrial situation with three phase power that confused the testers of copy machine companies but looked just fine on a multimeter.
I have not read every detail of your situation.
My problem was determined to be a "shared neutral".
Oxford

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Chris Smith
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Post by Chris Smith » Fri Aug 10, 2007 4:55 pm

Neutral wires and grounds are exactly like the highway and the paved shoulder.

They both go to the same place but ONE is designed specifically as a safety, and its not designed to be used as the main highway.

Using the shoulder doesn’t hurt anything, but in case of emergency, it can screw up everything.

b1miller
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Post by b1miller » Fri Aug 10, 2007 5:42 pm

Chris,
The NEC clearly distinguishes between a grounded conductor which will carry current under normal conditions and a equipment grounding conductor which is only intended to carry the fault current until the circuit breaker or fuse clears the fault current. They are not the same thing and should never be considered the same. One way to illustrate the difference is to look in NEC Article 250 where the equipment grounding conductor is sized. The NEC allows you to use, for example, a #8 AWG copper wire for grounding a circuit that is fed from a 100A fuse or CB. The NEC in Table 310.16 shows that the maximun rating for a #8 THHN at 75C is only 50A. The reason for the 100A rating is that the fault current is only a temporary or transient condition. The fact that both conductors are bonded together at the panel is irrelevant for current loads as far as the NEC is concerned. And the NEC will always be the defacto standard (and the law)as far as electrical installations on residential and the majority of industrial/commercial installations. In many cases the equipment grounding conductor can be a bare conductor without insulation. This is not a conductor that we would want to carry current except under fault conitions.
As an EE and journeyman electrician, I am concerned when someone does not clearly distinguish between the 2 types of conductors.

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Chris Smith
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Post by Chris Smith » Fri Aug 10, 2007 6:58 pm

B1

If you’re a journey man and have worked on houses, then you know they are exactly like the road reference.

One was designed as a safety back up, not to be clogged with every day usage, the other is a main throughput for the traffic.

Because both do go to exactly the same place, then cutting off at 90 degrees on the neutral wire, and then going to a dedicated local EARTH ground is 100% safe.

AT the most, some GFIs will not sense the fault as well, but then as Robert Said, the codes don’t even require a three wire system to improve this status of the GFI.

Your circuit will simply work better, especially of your main panel has a faulty neutral to ground connection.

Under no circumstances have I said simple use either, what I will say is any time your neutral is deficient [especially at the panel to ground connection] you can make that wire into a dedicated ground out side, using a pipe or what ever disperses the power before reaching the defective panel, to then do exactly the same thing,...go to ground.

IF you jump the neutral to ground pins on a wall socket, the only thing that can happen is you remove any safety protocol in place, but you don’t endanger the circuit at all, just the safety protocols.

Both wires go to the panel, both wires are the same size, both wires end up grounded from the panel to a dedicated earth ground.

To do so at the wall socket makes both into dedicated neutral wires at the expense of a safety wire.

Its like adding in two fuses, when one does the proper trick.

You should always leave your third wire, a ground, open for safety reasons.

It is perfectly safe to improve any neutral wire or plug, simply by making it into a perfect or semi perfect ground at the neutral connection, as close as possible to the plug. It already returns to earth, it just happens a lot later.

You can also do the same for the ground wire.

Almost 50% of all my customers computer frames leak voltage to the body of the frame, shocking any skin cut touched to that body.

A simply ground [#3] wire at the plug diverts that shock DIRECTLY to the ground wire right out side the window not relying on the pole grounds.

Also on the way back to the mains, the neutral wire [#2] also short cuts the long trip all the way back to the mains [100 feet away], using another ground wire at its pole.

I add in a extra neutral to ground wire which is dedicated to earth less than 20 feet away at that particular panel.

In simple, the neutral and ground rely on the mains, and then the ground at the panel.

I don’t.

I ensure they don’t have to travel so far to make up for any lost or wasted slack, due to length of leads or poor wiring connections.

I have at least six grounds around the place to ensure any lost return power doesn’t have to rely on one main feed wire from the power company to make the connection.

Drop a 120 lead on the ground and watch it spark, that ground and neutral return is better than you think.

This will give you an idea of a perfectly normal, safe, and better house wiring for any situation.

The upper one is the way your house is already wired.

The lower one provides more safety, and energy return.

http://img128.imageshack.us/my.php?image=120rt4.png

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