Ground Neutral Question

Thread Starter

les_garten

Joined Oct 3, 2013
4
Moderator Edit: This was split from here: http://forum.allaboutcircuits.com/showthread.php?t=14393

I bought a Lutron wireless switch to control a ceiling fan.

I need to cover up the switch with a painting and wanted to put in wireless since the switch would be inaccessible. So the wireless switch requires a Neutral since I suppose it needs a little power to run the radio and maybe trip a relay.

My original switch does not have a neutral. It's just a dumb switch that switches the hot wire and has a ground.

What would be the real life ramifications of using the ground as the neutral.
 
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#12

Joined Nov 30, 2010
18,224
If you do not have a neutral wire available in the switch box and use ground as the return current path, some millivolts of AC voltage will appear at the connection to the ground wire in the switch box.

Not lethal, but strictly illegal.
 

Thread Starter

les_garten

Joined Oct 3, 2013
4
If you do not have a neutral wire available in the switch box and use ground as the return current path, some millivolts of AC voltage will appear at the connection to the ground wire in the switch box.

Not lethal, but strictly illegal.

Could you touch a ground wire and get a little buzz maybe?

I've been around mobile homes that had metal stair rails that you could get a buzz walking up into the trailer.

Thanx by the way!
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
There a couple of unsafe scenarios that could happen.
The ground conductor on its way back to the panel is probably grounding other objects and fixtures which are exposed to human contact.
If you were to use the GND wire as a neutral and it happened to open accidentally or intentionally, this would make any metallic object it was connected to between your connection and the break become live.
Also if it were opened by someone unsuspectingly in carrying out wiring, full voltage could exist at the point of the disconnection.
Max.
 

WBahn

Joined Mar 31, 2012
29,979
I'm not conversant with European power distribution, but American residential power is split single phase, not three phase. That's 240 between the hot leads and 120 from either hot lead to ground. American residential hot leads have current 180 degrees apart, not 120 degrees as is found in 3-phase.
Power distribution in the U.S. is predominantly 3-phase. Residential split-phase is derived from one of the phases for any particular residence. As noted elsewhere, the assignment of residences and other utility loads is spread across the three phases to achieve approximate balance.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
Power distribution in the U.S. is predominantly 3-phase.
No real difference from any other part of the world, the predominant feature is that rather than use the phase to neutral direct, N.A. uses a local single phase transformer to obtain a 240v centre tapped supply with the centre tap creating a earthed neutral.
Max.
 

Thread Starter

les_garten

Joined Oct 3, 2013
4
There a couple of unsafe scenarios that could happen.
The ground conductor on its way back to the panel is probably grounding other objects and fixtures which are exposed to human contact.
If you were to use the GND wire as a neutral and it happened to open accidentally or intentionally, this would make any metallic object it was connected to between your connection and the break become live.
Also if it were opened by someone unsuspectingly in carrying out wiring, full voltage could exist at the point of the disconnection.
Max.
Yes I see, that makes sense.
 

studiot

Joined Nov 9, 2007
4,998
We have members in remote areas of both Canada and Australia that have pointed out the use of single conductor (Phase only) AC supply with the local return terminal connected to local ground.

This does work and saves considerable wiring cost. It is most suitable where there are single or few consumers at the ends so that there are not big fluctuations of created by voltage by mass switching on / switching off.

It is becoming obsolete.
 

sheldons

Joined Oct 26, 2011
613
that is definitely not allowed to be wired like that here in the uk due to the fact if theres a fault it would make exposed metalwork live and if the earthing isnt quite up to standard there would be a shock hazard....what you need to do is fit it at your ceiling rose where you have an accessible live feed and neutral that way your wall switch isnt disturbed wiring wise and your safety earth remains a safety earth....
 

WBahn

Joined Mar 31, 2012
29,979
We have members in remote areas of both Canada and Australia that have pointed out the use of single conductor (Phase only) AC supply with the local return terminal connected to local ground.

This does work and saves considerable wiring cost. It is most suitable where there are single or few consumers at the ends so that there are not big fluctuations of created by voltage by mass switching on / switching off.

It is becoming obsolete.
Really? I was reading about this system just this afternoon -- guess it started in New Zealand in 1925 or so -- and it said that it was expanding and becoming more common. It cited specifically in the U.S. northwest and prototype networks in Alaska.
 

WBahn

Joined Mar 31, 2012
29,979
that is definitely not allowed to be wired like that here in the uk due to the fact if theres a fault it would make exposed metalwork live and if the earthing isnt quite up to standard there would be a shock hazard....what you need to do is fit it at your ceiling rose where you have an accessible live feed and neutral that way your wall switch isnt disturbed wiring wise and your safety earth remains a safety earth....
The ground is isolated by transformers on both ends. The claim is that the safety record is comparable, if not better, than the traditional approach provided proper maintanence is done and that the lower cost of installation and maintenance encourages proper maintenance compared to traditional approaches. The reliability is said to be noticeably better, too.

Apparently one of the biggest problems is that lines coming into contact with moderate resistances to ground, such as through a tree, may not be detectable as a fault and arcing in the tree (or whatever) can cause fires in cases where a traditional system would have faulted. But, by the same token, a significant cause of faults and fires traditional systems can be lines coming into contact with each other and that is not a possibility with single line ground return systems.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
Apparently one of the biggest problems is that lines coming into contact with moderate resistances to ground, such as through a tree .
The return path is unpredictable, both ends are connected to a 12,000 Km Dia spherical conductor .;)
Max.
 
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t06afre

Joined May 11, 2009
5,934
From this book http://books.google.no/books/about/Grounds_for_Grounding.html?id=1WfPWbSN7pUC&redir_esc=y
Historically, the first functional application of grounding evolved in telegraphy. Longdistance electromagnetic telegraph systems from 1820 onwards used two or more wires to carry the signal and return currents. It was then discovered, probably by the German scientist Carl August Steinheil in 1836–1837, that the earth could be used as a return path to complete the circuit, making the return wire unnecessary (Figure 3.4). However, there were problems with this system, exemplified by the transcontinental telegraph line constructed in 1861 by the Western Union Company between Saint Joseph, Missouri, and Sacramento, California. During dry weather, the earth connection often developed a high resistance, requiring water to be poured on the earth electrode to enable the telegraph to work or phones to ring [5]. Later, power engineers used the earth as a return path in single-wire earth-return (SWER) electrical distribution systems, in order to reduce the cost of wiring. This system is still in use in rural areas today. In the early years of the 20th century, the proliferation of electrical machinery and appliances caused fires and casualties. Practices for ensuring the preclusion of electrocution hazards associated with the utilization of electrical power were not totally understood. Resulting from this situation, grounding and earthing of electrical equipment were mandated for functional use. With the understanding of the lightning phenomenon, earthing was implemented for addressing the risk of lightning strikes and electrostatic discharges, both being a potential source of damage to equipment and hazardous to people and domestic animals. Since the current path for both lightning and static electricity appear to involve the earth, it seems only reasonable to connect all electric equipment and structures to the earth, or in other words, ground them, in order to provide a controlled path for conducting the discharge currents to the earth.
 

sheldons

Joined Oct 26, 2011
613
Here in the UK the protective Ground wire -be it for lighting or Ring circuits etc-is only used for that purpose for safety.......if you had no earth connection and the metalwork became live due to a fault there would be no protection against somebody getting a shock....could you post a pic/install info on the units you have ?
 

studiot

Joined Nov 9, 2007
4,998
Hello, sheldons.

UK practice has developed over the years. What was done in the (distant) past may have been different.

Here, where I am, we have what is left of the works of electricity pioneer Andrew Crosse, at Fyne Court.

I hope soon to visit Cragside, near you, to see the works of your pioneer.
 
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