Neutral and ground merged in USA...

Thread Starter

Externet

Joined Nov 29, 2005
1,847
Hi
What if neutral and ground were NOT bonded together ? What problems are to surface, or safety concerns ? What if by building code, neutral and ground were supposed to be kept separate in households wiring ? What would be different with metallic breaker panels, distribution boxes, conduits, appliance chassis, outlets respecting the separation being 'ground' a copper rod into the soil ground and neutral a 'power' only wire from the pole ?

Would it be different on a concrete building than it is on typical wooden dwellings ?
 

crutschow

Joined Mar 14, 2008
29,810
What if neutral and ground were NOT bonded together ?
The reason for grounding the neutral is so that the two main wires are not floating, which means they could accumulate a significant static charge and damage insulation.
Neutral is neutral because it is connected to ground.
Grounding the neutral has nothing otherwise to do with safety.
 

MaxHeadRoom

Joined Jul 18, 2013
25,214
Neutral is neutral because it is connected to ground.
Although in a service where the domestic supply is one phase of a 3 ph transformer and the star point is a Neutral. grounded or not.
e.g. UK etc.
The same could also be said of a N.A. system where the neutral is a 0v C.T. of a secondary.
 

Ian0

Joined Aug 7, 2020
5,154
if neither conductor is earthed, then it is an IT earthing system. It is single-fault-tolerant, so either conductor could be shorted to ground, and no fault could be detected. Only on the second fault does it cause any circuit breakers to trip.
It is the earthing system that you have when you use an isolating transformer. It is useful in preventing shock is such situations, but only used when only one load can be connected to the source, because after the first fault occurs it becomes a shock hazard.
 

Rich2

Joined Mar 3, 2014
241
My small generator isn't earthed, I have to earth one of the outputs or the central heating boiler goes into fault code. The motorhome inverter isn't earthed either, that runs the TV ok though.
 

LowQCab

Joined Nov 6, 2012
2,055
Power is locally distributed to your House using just 1-Wire,
with a Grounding-Rod on every Power-Pole as the other Conductor,
( so the whole system is grounded about every ~100-feet or so ).

This means that there is no way that your "Neutral-Conductor" could NOT be connected to Ground.
But when Current flows though a Wire, a Voltage-Drop is created,
its usually a very small Voltage, but it could still be dangerous under certain circumstances.

The rules for Residential-Grounding are for minimizing any Voltage-potential between
any metallic-appliance and Ground for personnel-protection.

This definition should help clear things up ........
Neutral-Conductors are "Grounded" "Conductors", because they normally carry Current.
Ground-Wires are NOT called "Conductors", because normally zero-Current flows on them,
therefore they are "Grounding" Wires, or "Bonding" Wires, NOT a "Ground-Conductor"
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.
.
 

DickCappels

Joined Aug 21, 2008
8,710
One reason neutral is grounded is to that if a short from line to the chassis of an electrical appliance, a clothes washing machine for example, a fuse would blow a the breaker would trip, thereby protecting people who might come in contact with the chassis.

#1 reason they are bonded together is because the electrical code says so. Don't try to outsmart the guys who write the standards.
 

MaxHeadRoom

Joined Jul 18, 2013
25,214
One example of where a neutral is 'created' is when an arbitrary selected secondary conductor of a 120v control transformer is connected to earth GND in order to provide a earthed neutral conductor.
This is in cases where the control voltage is required in a industrial enclosure and the reference to a 120v grounded supply has been lost due to an isolated service.
 

LowQCab

Joined Nov 6, 2012
2,055
"" N.A. has 3 wire residential distribution, 2 @120v and a Neutral. ""

That's only after the Transformer.
Your local transformer feeds 4 to 6 Homes in the average neighborhood,
that Transformer is fed with one Hot-Wire,
and a Grounding-Rod driven in to the ground.
No separate Bonding-Wire runs from the Transformer to your Home,
( it may carry some Current, therefore it's a Grounded "Neutral-Conductor" ).
The Home must also have a Ground-Rod driven into the ground,
the Bonding-Wire from that Ground-Rod connects to a single point inside the Electric-Meter,
along with the incoming, and out going, Neutral-Conductors,
and then "may" split-off into a separate Neutral-Conductor, and a separate Bonding-Wire,
when entering the Circuit-Breaker-Panel or Fuse-Box.
( Some very old Homes don't have a separate Bonding-Wire in the Fuse-Box )
.
.
.
 

DickCappels

Joined Aug 21, 2008
8,710
Power is locally distributed to your House using just 1-Wire,
with a Grounding-Rod on every Power-Pole as the other Conductor,
( so the whole system is grounded about every ~100-feet or so ).
For contrast, in my house in North-Eastern Thailand if fed by two wires - one line and the other neutral. Ground for the outlets is achieved with a long copper rod driven into the ground next to the house (most of the year the water table is less than 2 meters down).

When all the underground wires from the street to the house shorted, became waterlogged, or otherwise failed (not the best electrician) the electric company flew two wires to the house, the telephone and two internet providers flew their new wires, and my electrician (not the guy who wired the house under construction) treated the shorted 240 VAC doorbell wires as a single conductor and achieved a ground return with a short copper rod driven into the earth. Everytime the doorbell rang I cringed thinking about the subterranean life in the path.
 

BobaMosfet

Joined Jul 1, 2009
1,979
One reason neutral is grounded is to that if a short from line to the chassis of an electrical appliance, a clothes washing machine for example, a fuse would blow a the breaker would trip, thereby protecting people who might come in contact with the chassis.

#1 reason they are bonded together is because the electrical code says so. Don't try to outsmart the guys who write the standards.
There is a lot of confusion about this, but here is how it works- Dick is right, but what trips most people up is WHERE the bond is. Just because Neutral and Ground are bonded at the breaker panel DOESN'T imply they complete a circuit. In order for the circuit to complete, an appliance must fail such that current finds the ground (like the chassis) in the appliance, and current then finds its way back to the breaker panel through a fuse, which trips and disables the circuit before a human becomes the alternate pathway.

Always use a neutral and ground properly, never use cheaters. Whatever a fix costs is far, far less than your life/limb to you, or your loved ones.
 

nsaspook

Joined Aug 27, 2009
9,740
"" N.A. has 3 wire residential distribution, 2 @120v and a Neutral. ""

That's only after the Transformer.
Your local transformer feeds 4 to 6 Homes in the average neighborhood,
that Transformer is fed with one Hot-Wire,
and a Grounding-Rod driven in to the ground.
No separate Bonding-Wire runs from the Transformer to your Home,
( it may carry some Current, therefore it's a Grounded "Neutral-Conductor" ).
The Home must also have a Ground-Rod driven into the ground,
the Bonding-Wire from that Ground-Rod connects to a single point inside the Electric-Meter,
along with the incoming, and out going, Neutral-Conductors,
and then "may" split-off into a separate Neutral-Conductor, and a separate Bonding-Wire,
when entering the Circuit-Breaker-Panel or Fuse-Box.
( Some very old Homes don't have a separate Bonding-Wire in the Fuse-Box )
.
.
.
power.png
https://electrical-engineering-portal.com/primary-distribution-circuits
 
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Rich2

Joined Mar 3, 2014
241
When I was at college years ago I'm sure the lab had an isolated supply for safety reasons. It consisted of a 1:1 transformer to separate earth from neutral. You would have to touch both lives at the same time to get a shock so a faulty machine's live chassis would do nothing because your not stood on the other conductor.

When you think, we walk on the earth so why connect it to one of the conductors? Seems like asking for trouble to me.
 

Ian0

Joined Aug 7, 2020
5,154
The lab would need to have a transformer for each socket to be safe.
If a single transformer supplied the entire lab, then imagine what would happen if one student shorted power to ground.
No-one would know - everything would work as normal, no fault would be detectable, until someone touched live. Then there would be the same shock as if there were no isolation transformer.
 

Thread Starter

Externet

Joined Nov 29, 2005
1,847
...we walk on the earth so why connect it to one of the conductors?...
I have lived in countries where all dwellings are entirely made of masonry and in countries where dwellings are made entirely of wood.

With masonry under your feet, touching live phase shocks you. Rubber soles prevent it.
With wood under your feet, you are isolated to a good degree and maaaany times got no shock when touching live phase.

Would this have something to do with more or less shock risk in USA wooden dwellings as ground and neutral are together ?
 
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DickCappels

Joined Aug 21, 2008
8,710
And if you live in a country in which floors are ceramic tile (conductive) and people walk barefoot inside the dwellings...?

When I have trouble with mains wiring (a regular event because of the shoddy electrical work) I always call an electrician.
1651671279734.png
I hate getting shocked and if he is willing to take the risk for US $20 it is well worth it to me.

Don't touch either line or neutral because sometimes the get swapped, only touch ground.
 
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