neutral bar
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Its at earth potentail...
or should be!
L - N =230V
L - E =230V
N - E = 0V
or should be!
L - N =230V
L - E =230V
N - E = 0V
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If you disconnect the neutral on a live circuit...
the "neutral wire" "Blue" or "black old money" is now at 230v with respect to earth!
consider a normal circuit path e.g.
1] supply L [230v to E]
2] live / phase wire [230v to E]
3] load [across the 230v]
4] neutral wire [0v to E]
5] supply N [0v to E]
If we have a fault on the neutral..
1] supply L [230v to E]
2] live / phase wire [230v to E]
3] load [230v to E]
4] neutral wire [230v to E] This neutral now LIVE!!!!
\/\/\/\/\/\/\/\/\/\/\/\/
4a] Fault open circuit 'N'
/\/\/\/\/\/\/\/\/\/\/\/\
4b] neutral wire [0v to E]
5] supply N [0v to E]
HTH. :|
the "neutral wire" "Blue" or "black old money" is now at 230v with respect to earth!
consider a normal circuit path e.g.
1] supply L [230v to E]
2] live / phase wire [230v to E]
3] load [across the 230v]
4] neutral wire [0v to E]
5] supply N [0v to E]
If we have a fault on the neutral..
1] supply L [230v to E]
2] live / phase wire [230v to E]
3] load [230v to E]
4] neutral wire [230v to E] This neutral now LIVE!!!!
\/\/\/\/\/\/\/\/\/\/\/\/
4a] Fault open circuit 'N'
/\/\/\/\/\/\/\/\/\/\/\/\
4b] neutral wire [0v to E]
5] supply N [0v to E]
HTH. :|
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Its safe as long as you don't disconnect it from the bar and grab the end , not to be recommended Dan, so its part of the live circuit . Or say as flow and return , its the return. It is carrying the return current . The neutral is earthed by the supply company at the star point at source so that those currents are carried safely away but not using the earthing system of a building.
Perhaps someone else can explain it more clearly , I'm starting to waffle.
deke
Ah ! Specs has already done it . Applaud Smiley
Perhaps someone else can explain it more clearly , I'm starting to waffle.
deke
Ah ! Specs has already done it . Applaud Smiley
green-hornet
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No you did fine
stick your tester between an open neutral and you will soon see why its treated as live
Specs,s posts are much better coz they are in colour , I,m still in B&W 405 lines.
He waffles on the same as myself but almost makes sense in colour !! ; \
Deke
, I,m still in B&W 405 lines. He waffles on the same as myself but almost makes sense in colour !!
; \Deke
thats still 404 lines more than my reply!Specs,s posts are much better coz they are in colour
Deke
the point im getting at is that,we treat neutral as tho its at 230v(i do anyway)yet in a CU its not insulated.if a few circuits are using power then 230v is going to be returning via neutral right?so is the neutral bar not then live? ?:|
Neutral will be at or around 0V unless there is a fault, in which case it may rise. If a circuit goes O/C, neutral will go to higher voltage. in a house, thats 230V. if its 3 phase, depending on loading, it could get to 400V
And you will find some DB's do have insulation covers for neutral bars
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Your just a tight wad and don't want to pay the full colour licence to Admin!!!!Specs,s posts are much better coz they are in colour
Deke
stick in the mud b&W licence's:_| X(
Maybe meet half way and give an extra colour for same price? like black, blue and white?!
well i have now paid for a COLOUR license from admin cost me an arm, and a leg, and my nose though :^O :_| :_|
green-hornet
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I still get mixed up withbrown and red
septiclecky
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Better than getting knocked about until your black and blue
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The thing you have to remember Dan is..
Any voltage or "potential difference" is only relative between TWO points.
so when we say Live is at 230v it is 230v with respect to earth. ground soil, rock, terra firma.
That is how it is generated at the power station..
3 separate phases with reference to a common point wot is bolted, nailed, stuck, bonded, fixed to the earth we stand on.
Neutral is also bonded to earth so neutral is at 0v with respect to earth.
The load is put between the live and the neutral so it has 230v potential across it.
A physical neutral wire only can only become 230v with respect to earth if the neutral is disconnected further along the circuit to become open circuit with respect to earth.
Because we generally consider the dangers in relation to us getting a shock from a live part to earth and a correctly wired installation will NOT have any voltage on the neutral cable with respect to earth. there is no need to insulate the neutral bar.
It only becomes a problem during fault conditions,
or unsafe isolation practices,
e.g. working live whilst disconnecting cables on untested / isolated circuits.
Other than that a correctly installed & tested live installation will have zero volts between Neutral and Earth.
dunno if thats any clearer? :|
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you never get a good BROWN on pc's!!! X( :_|
Try it this way Dan, the Potential Difference between live (brown) and earth is 240volts . The PD between live and neutral is 240 volts. The PD between neutral and earth is 0 volts (zero) Notice in a metal dist board that the earth bar is bolted to the case but the neutral bar is insulated from the case but still open to the touch.
On 3 phase its a big deal if the main neutral is lost, 415 volts round all the circuits , lamps blowing, fluorescents really weird , not to be recommended again . So, as long as it remains connected all is well , and no its not " live" as in touch it and you get a shock as long as its connected , there is no potential difference between the neutral bar and you , both at the same potential so you feel nothing. You are right in saying that all the circuits will be returning to the bar but after the load, how can I put it, the returning current is at earth potential , if you pulled the main neutral out and grabbed the bar all that current would flow through you , with fatal results I must add . Do not try that at home.
Deke
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