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Does Current Flow on the Neutral?


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Salty Dog

There are a lot of people out there discussing this whole neutral thing and it can be a little difficult to understand what is going on without being able to see what is happening.

Let’s start this off by stating yes, current does flow in a neutral. But there are times when it doesn't. To understand this we need to look at exactly where in the circuit we’re examining. If we are near a device, somewhere in a branch circuit, there will most likely be current flowing at that point. If we look further forward in the circuit, to the electrical panel, this is where things get interesting.

If a panel is perfectly balanced, and we have 2 loads that we are looking at, then each of those branch circuits will have neutral current flowing throughout the entire branch(es). But the neutral from the electrical panel back up to the transformer, will not. When two loads are turned on, and are exactly the same, the neutral current can actually balance out and, in fact, cancel each other out.

Neutral conductors from a panel back to a source will carry any imbalanced current that exists between any two phases on the system.

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DeedleNuts

Not sure how that applies in PH unless the house is wired for 120v though. From what I've seen the premise wiring tends to be a little fast and loose here. 

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philuk

it must flow on the neutral, you have a live and a neutral on all appliances, disconnect either the live or the neutral, then the thing wont work,

it matters not which wire has the switch in it, but normally on the live wire so that the appliance is dead when turned off

many years ago some car manufacturers fed the bulbs with a live wire and then to the switch to be turned on or off, this made the switch last longer due to the resistence in the bulb, now it is done with relays 

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DeedleNuts
1 hour ago, philuk said:

this made the switch last longer due to the resistence in the bulb

Kirchoff's law says neyt.

What it does is sometimes simplify the wiring, and auto manufacturers will kill for a nickel per unit. If you have trouble seeing why compute the voltages and currents in the circuit in both scenarios with the switch open and closed. Closed, the current is the same and the voltage drop is almost zero across the switch, and open the current is zero and the voltage drop is all across the switch.

1 hour ago, philuk said:

t must flow on the neutral, you have a live and a neutral on all appliances

The first statement is false because the second is false. If they don't bother to ground one leg, it's not a neutral. It is, often, really more fun in the Philippines. If the appliance (in USA particularly but applies anywhere) does not use a neutral, also false. But in cases where a neutral is present and used, of course current must flow if the circuit is to be complete. 

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philuk

The second paragraph confuses the issue, in the Philippines there is very often two live wires, as in two phases, without a neutral, so current cannot not flow through a neutral that does not exist. but if the appliance is fed from a single live wire, as in the UK and uses a neutral to ground, then current must flow through the neutral to complete the circuit. 

You cannot liken a none neutral circuit to a live / neutral circuit. they work differently, so therefore my my statement is correct. 

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DeedleNuts
4 hours ago, philuk said:

in the Philippines there is very often two live wires,

True

On 8/9/2022 at 5:37 AM, philuk said:

you have a live and a neutral on all appliances

False

 

I can't say it any more simply. 

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DeedleNuts
4 hours ago, philuk said:

two live wires, as in two phases

Also not correct use of the term phase, I believe. I'm not sure in foreign lands on this one but generally for a live wire to be of a different phase the voltage can't be in phase or 180 out of phase (which is essentially also in phase) with respect to the line it's being compared to. For example 120 USA standard supply (live and neutral) and 240 v standard USA supply (two live wires, both 120v from neutral and 240v from each other) are single phase. They are generated by a single loop. 

https://d2vlcm61l7u1fs.cloudfront.net/media/e99/e99f36f0-42f6-4afd-8f37-7d199c3b7baf/phpu8jyGa.png

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DeedleNuts

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philuk

Dual phase — alternately known as split phase — is basically the same thing as single phase. Dual phase consists of an Alternating Current (AC) with two wires. In the United States, the typical power setup in households consists of two 120 V power wires — a phase A and a phase B, which are out of phase by 180 degrees. Many prefer this approach for its flexibility.

the diagram above is taking a leg from each end of a coil in a similar manner an inverter splits single phase into three phase. the the two legs as they commonly known are 180 degrees out of phase, you cannot make 240 volt with two 120 volt feeds if they are the same phase, the middle tap on the coil is a ground wire used for neutral, 

If you look at the diagram it shows the aircon being fed from two 120 volt legs with no neutral, if these were the same phase it can not work, whereas the tv is fed with a single leg and a neutral so it gets 120 volts and a neutral and will work 

for instance if you join two car batteries in parallel you still get 12 volts, if you join them in series you get 24 volt, now take a live feed from each battery and connect to either side of a bulb, does the bulb light up.

I have seen this diagram before and the author also states that Europe three phase is 460 volts when in fact it is 415 volts the Philippines is 380 volts.

Edited by philuk
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A_Simple_Man
3 hours ago, philuk said:

In the United States

Ah yes.  But this is Philippines we are talking about.  One hot wire and one neutral cable to most rural houses.  One phase . . variable voltage . .  depending how many sharing the line.

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DeedleNuts
4 hours ago, philuk said:

Dual phase

Please refer to the diagram label for more clarification. 

https://en.wikipedia.org/wiki/Two-phase_electric_power

That's two phase power, different thing. 

 

4 hours ago, philuk said:

the author also states that Europe three phase is 460 volts

Compared to what? With three phase power, 480 volts phase to phase will be (if the transformer is a wye and the center tap is grounded and used for neutral) about 277 volts to neutral, 208 3 phase is popular due to it being suitable for larger motors and the same setup yielding about 120 to neutral for single phase loads. I didn't do the math but I bet 415ish is popular in EU for a similar reason, easy to derive 240 single phase from it 

On 8/9/2022 at 5:37 AM, philuk said:

you have a live and a neutral on all appliances

4 hours ago, philuk said:

If you look at the diagram it shows the aircon being fed from two 120 volt legs with no neutral

Yes that would be an example of an appliance without a neutral, thanks for noticing. 

Edited by DeedleNuts
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DeedleNuts
1 hour ago, A_Simple_Man said:

Ah yes.  But this is Philippines we are talking about.  One hot wire and one neutral cable to most rural houses.  One phase . . variable voltage . .  depending how many sharing the line.

Yeah my current condo makes the 'grounded shield' of USB plugs and the AL housing of my laptop carry just enough residual potential to feel. I can't like it, moving soon. How they don't die or set everything on fire is a mystery. 

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DeedleNuts

image.thumb.png.e6283cbd8a5716508f7446b475fb47d3.png

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trthebees
11 hours ago, DeedleNuts said:

Yeah my current condo makes the 'grounded shield' of USB plugs and the AL housing of my laptop carry just enough residual potential to feel. I can't like it, moving soon. How they don't die or set everything on fire is a mystery. 

Disclaimer!...I clearly can't have a comment on your condo wiring or the safety of your appliances!!

But having said that, metal casings can have a noticeable tingle when there is no independent earth due to the leakage action of the interference (EMI) filter. These like an earth to work most efficiently.

Note...independent earth..not , as with Cebeco, connected via the earthed neutral. If the neutral became disconnected, you'd see 240V on the casing!

In my first house in the Philippines we had no earth...the computer casing tingled. In our second I've run an independent earth with rod around the sockets which neatly picks up the  EMI leakage from the computer, aircon, fridge etc. so that the metal casings don't tingle. 

I;ve tested it...disconnect the earth and the tingle builds up! I would add that I have fitted a 30mA RCD, which would have tripped if the tingle was a serious fault.

It's a thing with appliances (electronic or rotating), many are double insulated with plastic casing. the house sockets are 2 pin. But in the instructions they may ask for an earth to be connected. Not a problem in the UK with our beefy 3 pin sockets!

Some years ago, when Woolf was with us, we had a good thread going on this topic, viz;

https://www.livingincebuforums.com/topic/109614-philippine-electrical/page/3/?tab=comments#comment-1490958

 

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DeedleNuts
3 hours ago, trthebees said:

the house sockets are 2 pin.

Here the receptacles are 3 pin but god only knows what the service wiring actually looks like. It doesn't feel dangerous but I can't like it. 

Feels like the neutral is floating a bit if I had to guess, and no proper (separately derived is I think the NFPA term) ground. 

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