USA neatral wire continued

restez · Nov 19, 2011

im confused what I don't understand is how the is applied in household mains current, split-phase 120/240V.

I am trying to understand, is current coming from the hot black wire first(main breaker panel 15 amp ) going to say outlet in home on one side gold screw goes through the load (outlet )comes out on the white neutral wire (silver screw) goes back to main panel to neutral bar then reverses back through white wire back through outlet back through black wire to the main panel out to the power plant ? or are they just switching and coming through the neutral white when the sine dips into the negative? This just sort of confuses me, because the neutral leads in the distribution system are not treated with the same caution. I mean, the neutral line from the service tap isn't insulated, and at the main panel the neutral lug bolts right to the chassis. How come current doesn't jump and zap you when you touch it? can someone tell me how electrons travel from the main panel though outlet and back or did i just do that
Thanks

WDMDL · Nov 19, 2011

The neutral is grounded. So as long as the neutral is intact, there will only ever be a very small voltage from neutral to ground on a circuit.

On split 120/240V circuits, both hot lines are 180 degrees out of phase. so that's why there's 120V between any and neutral, but 240V between both hot lines.

Now on a large dual voltage appliance eg a cooker, half the heaters are connected between hot 1 and N.
The other half are connected between hot 2 and N. So each causes a neutral current flow in the opposite direction to the other at all times.
So, the neutral current will be at its highest if you somehow manage to choose all the heaters fed from one hot only.

You could have 4 rings on the hob at full output with a resulting neutral current near zero. (assuming all were the same rating)

Simon.

Engineer54 · Nov 19, 2011

WDMDL said:
The neutral is grounded. So as long as the neutral is intact, there will only ever be a very small voltage from neutral to ground on a circuit.

On split 120/240V circuits, both hot lines are 180 degrees out of phase. so that's why there's 120V between any and neutral, but 240V between both hot lines.

Now on a large dual voltage appliance eg a cooker, half the heaters are connected between hot 1 and N.
The other half are connected between hot 2 and N. So each causes a neutral current flow in the opposite direction to the other at all times.
So, the neutral current will be at its highest if you somehow manage to choose all the heaters fed from one hot only.

You could have 4 rings on the hob at full output with a resulting neutral current near zero. (assuming all were the same rating)

Simon.

The theory is OK, except that American cookers are fed by 3 pin outlets, ...L1, L2 and earth. Same with there washing machines, and other 240 volt higher power circuits.

Oh, and it's a single phase 3 wire system the transformer center tapped and earthed to give a neutral and the 120 volt supply

GLENNSPARK · Nov 19, 2011

I think they have several different voltages in america dont they?......

Engineer54 · Nov 19, 2011

They do indeed, but the 3W single phase system is the norm for domestic dwelling installations. The other supplies are generally for industrial/commercial installations. One of them being a delta secondary supply with one leg earthed!! In all i think it's around 5 or 6 different LV supplies that are available, depending on what State your in...

WDMDL · Nov 19, 2011

Engineer54 said:
The theory is OK, except that American cookers are fed by 3 pin outlets, ...L1, L2 and earth. Same with there washing machines, and other 240 volt higher power circuits.

Oh, and it's a single phase 3 wire system the transformer center tapped and earthed to give a neutral and the 120 volt supply

Oh right. I picked up a book on electrical installations when I was over there and I thought that' was how the cookers were wired.

I knew how the transformer setup gave the 120 and 240V supplies though.

Simon.