Neutral-ground bonding for wall receptacles

Amos Kariuki wrote:


Use your common sense and compare the nature of the connections at the neutral buss, meter enclosure, demarcation point (the splices that connect your service entry conductors to the utility's supply conductors), with those that are made in an outlet box. The ones at and before your Service Disconnecting Means (SDM) are tightened by the most experienced wireman on the job, using torque measuring tools, with anti corrosion paste applied. They are then closely inspected by the electrical inspector and checked by the utility company's outside wiremen prior to power being applied. Which of the two do you think is more likely to suffer a failure? That doesn't mean that they cannot fail because they can and do but that is a far less frequent fault then an open neutral on a back stab receptacle in one of dozens of outlet boxes most of which were made up by the least experienced helpers who are being pushed for production. Just as importantly the bonding that is done during the construction that keeps all of the conductive surfaces at the same voltage reduces the likelihood of a fatal shock and the malfunctioning of the served loads in the entire home provides the impetus for the occupants to report the trouble and have it cleared. If just one circuit is affected the occupants are more likely to try to muddle through and the other conductive surfaces in the building are not at the same elevated potential as the bonding pins of the faulted circuit. The 120 volt difference between various surfaces in the home makes a fatal shock far more likely. -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
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Amos Kariuki wrote:

If wired correctly, the neutral, which is a current carrying conductor, cannot come in contact with a human under normal circumstances. The ground, which is _not_ a current carrying conductor, is regularly in contact with humans at many metal case appliances and tools.
It is obvoius that you do *not* want a human to come into contact with a current carrying conductor. You want to keep the current away from the human. Here's a "picture" of what can happen.
------- Hot------------------|Recept |---Appliance---+ | | | Neutral--- Defect ---|Nuetral|---+-----------+ | | | | <Illegal | |Ground |---+ Connection | ------- | | | Ground-------You-----------------+
Because of the illegal connection, a defect in the neutral can expose you to danger. Current could flow through the appliance, the illegal connection and you back to ground. If the illegal connection was not there, the defect in the neutral would not expose you to the danger illustrated.
Ed
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On Mon, 7 Jan 2008 15:49:21 -0800 (PST), Amos Kariuki

How do you know the white wire is really grounded? Somebody night have swapped them on an upstream receptacle. Then what do you think you would have?
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On Tue, 08 Jan 2008 01:17:34 -0500, snipped-for-privacy@aol.com wrote:

How do you know the green wire is really grounded?
Chuck
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wrote:

It is very common to find white and black swapped in receptacles.
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snipped-for-privacy@aol.com wrote:

I've run into several places where the wire is spliced to another color, and pulled through conduit. One was pink at on end, and yellow at the other end. :( It was between floor outlets in a school office, and the janitor had removed the screw in covers before using a floor scrubber. Then he put them back, without the rubber seals. The conduit was full of dirty water and floor wax. The power for the school's intercom system ran through the same conduit, and it had opened, due to electrolysis. I though I was going to need a blasting cap and new conduit, but after a couple hours of work, I managed to open the conduit enough to run new wire. Needless to say, it was an expensive repair, and they fired that janitor, before they found other stupid things that he'd done.
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On Tue, 08 Jan 2008 11:54:32 -0500 snipped-for-privacy@aol.com wrote:
| wrote: | |>>How do you know the white wire is really grounded? Somebody night have |>>swapped them on an upstream receptacle. Then what do you think you |>>would have? |> |>How do you know the green wire is really grounded? |> |>Chuck | | | It is very common to find white and black swapped in receptacles.
And no one, trying combinations to see what works, would ever hook up a receptacle between black and green?
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alt.engineering.electrical, snipped-for-privacy@ipal.net says...

Not nearly as likely, I suspect. The "green" terminal on most fixtures is, well, green. Many people don't know there is a difference between the other two or that outlets are polarized. At one time there wasn't and they weren't.
--
Keith

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snipped-for-privacy@ipal.net wrote:

It is at least less likely because the ground screw is usually painted with green metallic paint. It is somehow beyond some people to match the black to the brass colored screw and the white to the silver colored screw. Then you add in the conductors that the painters spray gun made the same color as the room's finish, the ones that are so old that the original color coding is gone... -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
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| It is at least less likely because the ground screw is usually painted | with green metallic paint. It is somehow beyond some people to match | the black to the brass colored screw and the white to the silver colored | screw. Then you add in the conductors that the painters spray gun made | the same color as the room's finish, the ones that are so old that the | original color coding is gone...
So I guess we need to paint the other screws for them?
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alt.engineering.electrical, snipped-for-privacy@ipal.net says...

It wouldn't be a bad idea. It would get the point across.
--
Keith

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We grounded ranges, cooktops, ovens, and laundry dryers for about 60 years using the neutral. They claim this practice was adopted during WWII to save on copper. Today in many older homes this practice remains in place. Although the NEC forbids this practice for 120 volt 15 and 20 ampere receptacles, I think it might be an acceptacle practice as it has proven to be safe for the ranges and dryers for many years.
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Gerald Newton wrote:

Range and drier circuits had to originate in the service panel and IIRC had to be connected with service entrance cable.
If you are talking about 15/20A circuits, there can be many splices back to the panel where the neutral can open or black and white be swapped. If wired correctly now, the black and white can be swapped when a receptacle is replaced.
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I beg your pardon; "originate at the service" for dryer and range circuits was not a NEC requirement for many years. I wired many four plexes where the circuits originated at the subpanel and that was to code. I also read that in some European countries they use the neutral for grounding. To me it makes more sense to use the neutral for grounding since if you lose it the circuit stops working. There is no way of knowing if you lose the grounding conductor or not unless you test for it.
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A lot of code rulings are partially based on probability. The probability of a ground/neutral connection opening up on a range or dryer (assuming it was installed correctly in the first place) is very, very low. These conductors are typically larger than other wiring and make a home run to the disconnect panel with few or no splices. This is why the neutral was also allowed to function as a ground for so many years.
Even though a very small (probably insignificant) number of "engergized dryer or range frame" accidents have been reported over the years, it is safer still to isolate the frame with a separate ground and keep the neutral separate, as well.
There is an added cost for doing this (running an extra wire to the junction box - using a four conductor instead of a three conductor hookup cord and plug, but apparently the authorities in charge think that it is worth it.
The new 2008 code is going to require arc-fault protectors in many new home spaces (instead of just bedrooms). Once again... this will be at added cost to electricians, new homebuilders, and new home purchasers. Once again, the code authorities believe that this will prevent a few fires from happening that might otherwise burn down your house.
Beachcomber
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On Tue, 8 Jan 2008 12:15:09 -0800 (PST), Gerald Newton

I am not sure when/if it changed but the 75 says it has to originate at the service. (The oldest book I have handy)
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Gerald Newton wrote:

For the code I just looked at the requirement was - insulated ground wire or - service entrance cable originating in the service panel.
That eliminates Romex unless it has an insulated ground wire but some methods could use a subpanel.
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wrote:

When they do use Romex you will typically see the bare ground wire going to the box or backstrap of a surface mount receptacle. The insulated white wire goes to the center pin of a 3 terminal receptacle. That is why I always have people look before they assume they can't convert to 4 pin receptacles.
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Gerald Newton wrote:

Gerald Once again, as I opined in another answer on this question, the difference is in the nature of the connections themselves. The circuit must originate in the Service Equipment enclosure, the conductors are heavier, invariably multi stranded, and the connections are made using single conductor terminals designed for the purpose. The rate of failures was perceived to be low enough to be acceptable. It was actually the advent of better data collection and analysis that was the three wire 120/240 volt circuits undoing. The NEC code making panel became aware that failures were far more common then was believed previously. -- Tom Horne
"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
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As I recall from reading the original Soares book on grounding where he devoted a whole chapter on the history of grounding, at one time in the early 1900's there was an international debate on whether grounded systems were better than ungrounded systems. As I recall at one time all the grounding was removed from the services in New York City because they thought ungrounded systems were the way to go. Eventually they decided that grounded systems provided superior protection for humans while ungrounded systems were better for not acting as a source of ignition for fires. But I still maintain that if the ranges and dryers could be grounded using a neutral for 60 years that this is a viable alternative that could work throughout the electrical system. Just because the code says it can't be done does not necessarily mean it is not a safe option. I for one am convinced there is a great deal of lobbying by the copper industry to use more copper in our electrical systems and that not all options are given equal opportunity when decisions are made.
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