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Wire Reverse between Life and Neutral

by masterbatmon
Tags: life, neutral, reverse, wire
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masterbatmon
#1
Nov13-06, 11:24 PM
P: 1
Hi,
I really want to know if there is a way to do detection whenever wire been reversed between Life and Neutral. Any opinion guys?
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chroot
#2
Nov13-06, 11:29 PM
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Neutral and ground, when properly wired, have zero potential between them.

- Warren
Danger
#3
Nov14-06, 12:14 AM
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Love your username, dude... although it would seem to perpetuate the science-geek stereotype.
If you have access to the connection points, you can just go by colour. (Here in Canukville, at least, the rule is black-gold/white-silver. White is system neutral, and black is hot.) If you have a black wire going to a silver terminal, somebody screwed up. Never take that as a given, though, because someone could also mess up the polarity of a plug if it wasn't part of the original wire (as in a lamp cord). Such things should always be checked with a meter. As Chroot said, if you show a potential between white and green (ground), it ain't proper.

NoTime
#4
Nov15-06, 11:19 PM
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Wire Reverse between Life and Neutral

There is a test plug that inserted into an outlet will show if its wired correctly.
You should be able to find one in a hardware store.
The cost is low, a few dollars.
Danger
#5
Nov15-06, 11:26 PM
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Quite right, but it might not always be practical to use it in some applications, such as a questionable appliance. While I have no trouble hooking something like that into something like a vacuum cleaner with jumpers, we can't assume that the OP can do so. For household wiring, your answer is absolutely correct. For things plugged into that wiring, however, a different approach might be necessary.
NoTime
#6
Nov15-06, 11:43 PM
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One step at a time
Given the number of houses I have seen that have incorrectly wired outlets, its probably something worth checking.
Danger
#7
Nov16-06, 09:28 AM
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Hmmm... I hadn't thought of that. Up here, household wiring, during the construction phase, has to be done by a qualified electrician or someone under the direct supervision of one. You would only encounter a faulty installation in the extremely rare case of a householder with no electrical knowledge replacing or installing an outlet on his own. Good point, though, especially if the OP is someplace with a lax construction code.
Panda
#8
Nov16-06, 10:04 AM
P: 220
This method works, but I do not advise anybody to try it unless they are sure that they have a consumer unit that can cope with this. This is not as far as I know industry prcatice but something I have taught my self by experience sorting out 100 years of bodged Gas, Electric and water in my home.

This assumes that you are starting with a consumer unit with an Earth Leakage circuit breaker (ELCB) each ring has either a fuse or an Residual Current Device (RCD)/ Residual Current Circuit Breaker with Overcurrent Protection (RCBO) on the Live wire. (This is UK by the way, I assume its the same where you live, hence don't try unless your sure).

On the ring that has the suspect wiring, pull the ring Fuse/RCD/RCBO to isolate the ring.
Now connect the Earth and Live together - Nothing will happen
Now Connect the Earth and Neutral together - The ELCB will trip due I believe to the small current imbalance on the Neutral Star Point at the local substation.

If the above happens you are wired correctly.
If the reverse happens your Luive and Neutral is crossed
If nothing happens your Earth connection/ELCB is faulty.
If you get electrocuted your rings are cross wired.

P.S. Check that the circuit is dead or ask ask your partner to stand nearbly with a broom to poke you off if you think you may have cross wired ring mains.
I had a power ring in one room that came from a spur on the lighting ring for the floor below.
Ramvich
#9
Nov22-06, 03:18 PM
P: 2
It does not matter in most cases if they are reversed on an AC system. The neutral in the US is grounded to facilitate the overcurrent protective devices, ie breakers. Some newer consumer devices have only 2 prongs on the power cord. These devices require the outlet to be wired correctly in order to have the protection of the circuit breaker. To answer your question all newer outlets have one slot in the outlet larger than the other. If you stick the probes from a meter, one into the larger slot and one into the ground hole and get a potential voltage the outlet is wired backwards. The larger slot is supose to be the neutral, and therefore should be no potential between them. And Danger was right about the color of the terminal screws. Gold for hot, silver for neutral and green for ground.
turbo
#10
Nov22-06, 04:14 PM
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For sure, spring a couple of bucks for a tester. I used to play guitar and sing in blues/rock bands and I got "bit" by my mic a few times until I smartened up and started checking the wiring of every outlet on every stage before performing. It seems that a lot of these old joints were wired by amateurs. Lots of the old Fender amps were made back before polarized, grounded outlets were common, so I either re-wired mine to conform to modern standards, or at least taped a little diagram with a short l and a long l to the plug to indicate how it needed to be plugged in. Actually, I ended up converting all but one amp eventually. There's a little gem of a blackface '65 VibroChamp that I want to leave as original as can be.
Averagesupernova
#11
Nov22-06, 07:26 PM
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Quote Quote by Ramvich View Post
The neutral in the US is grounded to facilitate the overcurrent protective devices, ie breakers. Some newer consumer devices have only 2 prongs on the power cord. These devices require the outlet to be wired correctly in order to have the protection of the circuit breaker.
Please don't post things like this. It is totally wrong. If too much current flows in the 'hot' wire no matter what the return path is the breaker will trip.
Panda
#12
Nov24-06, 02:16 AM
P: 220
Quote Quote by Ramvich View Post
It does not matter in most cases if they are reversed on an AC system. The neutral in the US is grounded to facilitate the overcurrent protective devices, ie breakers.
Do not ask this guy to work on your wiring.

Ground/Earth is NOT the same as AC Neutral.

There is always current flowing on your single phase Neutral, Unless you have 3 phase power the Neutral cannot be connected to Earth, and even in 3 phase only at a well balanced star point.

The reason why so many appliances have no Earth is because they are double insulated so it is theoretically impossible for AC current to be present on any external surface.
turbo
#13
Nov24-06, 07:07 AM
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Quote Quote by Panda View Post
Do not ask this guy to work on your wiring.

Ground/Earth is NOT the same as AC Neutral.

There is always current flowing on your single phase Neutral, Unless you have 3 phase power the Neutral cannot be connected to Earth, and even in 3 phase only at a well balanced star point.

The reason why so many appliances have no Earth is because they are double insulated so it is theoretically impossible for AC current to be present on any external surface.
Clean-up in aisle 3. Go look at the 220V entrance in your house (assuming that you are on a US-type entrance). Neutral is tied to ground. You should see no potential between neutral and ground at any outlet. In fact, if the neutral-to-ground connection at your entrance box is poor, when a big load comes on-line on one leg of your entrance, it will shift the potential of the neutral, lowering voltages on that leg, and raising the voltages on the other leg. This is a potentially dangerous condition. Neutral must be tied to ground.
Averagesupernova
#14
Nov24-06, 08:12 AM
P: 2,529
Ummm, yet another correction. Neutral MUST BE TIED TO THE CENTER TAP ON THE TRANSFORMER. If the neutral to transformer conntection is poor it will shift the voltage like turbo described. I prefer to say ground is bonded to neutral and not neutral is bonded to ground. Yeah, I'm being nitpicky but it implys that the neutral is the conductor instead of the ground being the conductor. A poor connection between neutral and the ground rod or water pipe has nothing to do with voltages shifting.
turbo
#15
Nov24-06, 10:28 AM
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Actually neutral IS the center-tapped lead from the transformer's secondary coil and the two 120V AC legs are the hot lines from the end taps of the secondary. If the neutral line is not firmly tied to ground at the entrance panel, large loads on either leg will cause voltage shifts. This happened in my old house a couple of years back. Linemen from the power company came to check the transformer at my request, then told me that the transformer was fine and that problem was probably a bad ground to neutral connection in my entrance panel. It was. 1/4 turn with a screwdriver cleared it right up.
Averagesupernova
#16
Nov24-06, 12:54 PM
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Quote Quote by turbo-1 View Post
Actually neutral IS the center-tapped lead from the transformer's secondary coil and the two 120V AC legs are the hot lines from the end taps of the secondary.
Yes, this is basically what I said in my last post.


Quote Quote by turbo-1 View Post
If the neutral line is not firmly tied to ground at the entrance panel, large loads on either leg will cause voltage shifts.
No, no, no, and.................................. NO! It has nothing to do with connection to what I call ground. If the neutral busbar where all the white wires attach to in your service panel has good continuity all the way back to the transformer then you can completely remove any grounding to ground rods and water pipes and your voltages will stay balanced. This is how mobile homes are wired. They have a neutral bus bar that is isolated from the ground bus in the service entrance panel. However, outside where the mobile home plugs into the ground and neutral will be tied together. Once again, you can defeat this ground connection and as long as the neutral is not disturbed and voltages will stay balanced. Ground is not meant to carry current except during a fault.

Quote Quote by turbo-1 View Post
This happened in my old house a couple of years back. Linemen from the power company came to check the transformer at my request, then told me that the transformer was fine and that problem was probably a bad ground to neutral connection in my entrance panel. It was. 1/4 turn with a screwdriver cleared it right up.

I don't doubt that a loose screw in the neutral conductor at your service panel would cause a voltage shift, but it has nothing to do with being bonded to what is correctly referred to as ground. I also don't doubt that this is what they told you.
turbo
#17
Nov24-06, 01:40 PM
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Quote Quote by Averagesupernova View Post
I don't doubt that a loose screw in the neutral conductor at your service panel would cause a voltage shift, but it has nothing to do with being bonded to what is correctly referred to as ground. I also don't doubt that this is what they told you.
Well, that was the screw that I tightened - the clamp on the neutral block that clamps the ground wire. The problem stopped instantly.
Averagesupernova
#18
Nov24-06, 06:41 PM
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Quote Quote by turbo-1 View Post
Well, that was the screw that I tightened - the clamp on the neutral block that clamps the ground wire. The problem stopped instantly.
What are you calling the ground wire? I'll post more later.


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