[Chris J]

Quote:

Well a aerial/antenna ground may have a very different purpose. I was a radio broadcast engineer. In the 1 MHz range, one half of the transmitting antenna is buried in the dirt. That's right, 1/2 of the local area radio signal flows through the dirt. That's 20 to 40 miles from the towers. The ground system is 100 or more radial wires buried in the dirt, each about the same length as the tower is tall.

Getting back to US NEC code requirements about ground rods. There is a trick rule in the book. The rule is that you may have one 8 foot rod if the earth/ground/dirt resistance is less than 25 Ohms, but to make that measurement requires a $2500 meter and about 1/2 hour time. So almost all electricians use the other rule that only requires two 8 foot ground rods separated by more than 6 feet. This is a simple summary because nothing in the NEC code book is simple. Almost every rule has hidden exceptions or requirements.

In the US more than 99 % of all homes have a 3 wire single phase 120.240V system.
The wires are
Hot #1
Hot #2
Neutral/Ground. Yep. over here, Neutral & Ground are the very same wire.

 
What?
In residential wiring, Neutral and Ground are bonded together in the Service Entrance Panel.
At the Service Entrance Panel a Ground Wire is run to Earth to bond Neutral to earth via cold water pipe, a ground rod or buried ground wire.
From that point on, Neutral and Ground are separate conductors.
From that point on, the Ground Wire is more properly called a Bonding Conductor.
Neutral is a current carrying conductor.
The Bonding Conductor is a non-current carrying conductor, unless it is carrying ground fault current or other exceptions.

 

[duncan1]

So ChrisJ- You are saying INTERNALLY they are separate conductors  but up until that time the positive[hot]  is all that comes in from outside.And that both the negative and ground are at the same potential at the main electric box?. In the UK the negative goes back to the power station and is earthed there. So money is saved by not running a negative wire back to the power station.??. Correct me if I have picked you up wrong.---Just like to add. The neutral only conducts to earth if everything is working properly. If the pos/hot wire becomes loose and touches the casing of a  piece of electrical equipment the current is taken directly to earth. if the casing is earthed.  

 

[Steve Eddy]

Power is delivered to homes via three wires, two are hot and one is neutral. For 120 volt service, one hot and neutral are used. At the entrance panel, neutral is tied to a ground rod and a second line off neutral is used for the safety ground (third pin on an IEC). 240 volt service (used for heavy appliances like clothes dryers) uses the two hots plus neutral.

se

 

[duncan1]

Well I am certainly getting different versions Now another from Steve Eddy But Steve is saying what I originally said -That like the UK  there is a pos[hot] wire PLUS a negative FROM THE power station / transformer[drop-down] external. But there is an ADDITIONAL pos[hot wire for heavy machinery  . In the UK they are only supplied to heavy engineering and is called  2-PHASE- although it is usually 3-PHASE. and are NOT supplied to residential properties. This gets more interesting as time goes on. Is there a difference between the US and Canada in mains wiring?? ---It ocurred to me that you might be saying that each pos[hot wire in a two hot wire setup are of the SAME phase --is that true.??- 3-phase in the UK is provided to factories  for 3-PHASE motors etc. the bottom line being it saves electricity and reduces POWER required saving the factory money. 

 

[Chris J]

Well I am certainly getting different versions Now another from Steve Eddy But Steve is saying what I originally said -That like the UK  there is a pos[hot] wire PLUS a negative FROM THE power station / transformer[drop-down] external. But there is an ADDITIONAL pos[hot wire for heavy machinery  . In the UK they are only supplied to heavy engineering and is called  2-PHASE- although it is usually 3-PHASE. and are NOT supplied to residential properties. This gets more interesting as time goes on. Is there a difference between the US and Canada in mains wiring?? ---It ocurred to me that you might be saying that each pos[hot wire in a two hot wire setup are of the SAME phase --is that true.??- 3-phase in the UK is provided to factories  for 3-PHASE motors etc. the bottom line being it saves electricity and reduces POWER required saving the factory money. 

 


Both Canada and USA use 120/240 Vac Split phase for residential wiring.
So NA residential wiring will get:
L1, N, L2 and Ground.
L1 is 180 degrees out of phase with L2.
This comes off your local distribution transformer.
Canada and US also use 208/120 Vac, 3 Phase for industrial wiring.
Main difference is USA also uses 480/277 Vac, 3 Phase.
Canada uses 600/347 Vac, 3 Phase for industrial distribution instead of 480/277 Vac.

 

[Chris J]

So ChrisJ- You are saying INTERNALLY they are separate conductors  but up until that time the positive[hot]  is all that comes in from outside.And that both the negative and ground are at the same potential at the main electric box?. In the UK the negative goes back to the power station and is earthed there. So money is saved by not running a negative wire back to the power station.??. Correct me if I have picked you up wrong.---Just like to add. The neutral only conducts to earth if everything is working properly. If the pos/hot wire becomes loose and touches the casing of a  piece of electrical equipment the current is taken directly to earth. if the casing is earthed.  

 

Forgot to answer this:
Neutral should always be grounded.
If a line wire becomes loose and touches casing then current is taken directly back to earth.......assuming your case is grounded and your power cord has 3 pins.
Don't call them negative and positive, this is AC wiring, not DC wiring.

reference:http://en.wikipedia.org/wiki/Earthing_arrangements

 

[duncan1]

Thanks for that ChrisJ-Its like a "potted" history of US/Canadian electricity output- The UK uses -440V-3 Phase for heavy industry. So you have =2 Phase in BOTH countries at varying voltages.for consumers.And theres me thinking --120V AC wont kill you like 240 in the UK but you have higher voltages as well. so the potential to be electrocuted is just as great in the US/Canada. 

 

[Chris J]

Quote:

Thanks for that ChrisJ-Its like a "potted" history of US/Canadian electricity output- The UK uses -440V-3 Phase for heavy industry. So you have =2 Phase in BOTH countries at varying voltages.for consumers.And theres me thinking --120V AC wont kill you like 240 in the UK but you have higher voltages as well. so the potential to be electrocuted is just as great in the US/Canada. 

 
Typically I have seen 416 Vac three phase equipment for the UK market.
240 Vac is actually one phase of 416 Vac three phase power.
 
The old European standard would be 220 Vac single phase, 380 Vac three phase.
 
I should add that US and Canada are both 60 Hz.
 
There is a common misconception that European neutral is different than North American Neutral.
In fact neutral in both zones is bonded to ground (earth).

 

[Chris J]

Quote:

3-phase in the UK is provided to factories  for 3-PHASE motors etc. the bottom line being it saves electricity and reduces POWER required saving the factory money. 

Three phase power doesn't save power or electricity.
This is a misconception which probably started from someone observing that less current is pulled at 480 Vac than it is at 120 Vac, but this is only because the 480 Vac is a higher voltage than 120 Vac.
 
What high voltage transmission really saves money on is in copper.
There is also a side benefit that you have less line drop at higher voltages for the same amount of power.