about the saying "neutral does not carry current"

Question

It came across to me quite frequently online that people state "neutral wire does not carry current." I thin this is a false statement. My reason is the following.

For the electrical panel in my home, I only saw three cables coming: red, black and white. I think the white is neutral. Red and black carry 120 V signal with opposite phase. For most breakers on my panel, only two wires are connected, either red and white or black and white.

Let's take red and white for example. The red and white wires will go from the breaker to appliance, say a toaster. When toaster is working, a current flows in the circuit, and I think there is equal amount of current in the red and white wires. Thus the neutral white does carry current.

Why the current on neutral won't hurt people? My understanding is that although it carries current, the potential difference from neutral wire and ground (e.g. home subfloor or true electrical ground) is very small (less than 1 V according to my measurement). Therefore, even if you touch the neutral with bare hands, the current (could be large!) on the neutral wire won't enter your body, because the neutral wire is so much more conductive than human body that effectively all the current flows only on the neutral wire, bypassing the human body.

Please correct me if I am wrong. Thanks!

Answer 1

That saying is wrong. It's dead wrong. The people saying it are idiots. Or you misunderstood.

Imagine if you found an SE post that started out "People often say 'humans do not contain blood'. I think that's a false statement." It's like that.

Neutral certainly does carry current. In a single-phase, 2-wire circuit with neutral, neutral carries exactly the same amount of current as the hot. Neutral is the normal current return.

Now in split-phase or 3-phase where 2+ hots and neutral are brought along, it's likely most of the load will be phase to phase, with neutral carrying only imbalance current. In multi-wire branch circuits, all loads are phase-neutral and neutral acts as a broker to try to return current via another load rather than bringing it back to the panel itself. But neutral is still a normal and legitimate carrier of current, and it counts.

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A great deal of work is done to assure that Equipment Safety Ground is at roughly the same voltage as the dirt surrounding your house. That way if you are touching a grounded receptacle while standing on your wet grass in your bare feet, nothing happens.

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We also make very strong effort to make neutral reasonably close to ground potential. Nobody cares if neutral is 7.3 volts away from the dirt in your lawn. We just want it to be close enough to be safe.

It's true if you are standing barefoot on your lawn and you touch neutral, you shouldn't be shocked. But that's not the main reason to do it. The main reason is to assure that your "hot" wires are only 120V from the dirt in your lawn. Consider the alternative. Imagine some leakage in the transformer caused your supply to float 2400V above where it should be: Hot 1 would be 2160V from earth, neutral would be 2400V from earth and hot 2 would be 2640V from earth. Now suddenly, touching any wire with your bare feet would be instantly lethal.

By providing a firm neutral-ground bond, in one place, we assure that neutral will be near 0V from earth, and the hots won't be terribly far away either.

Picking any supply wire and bonding it to earth in this way defines that wire as neutral. Neutral need not be "in the middle".

Answer 2

You need to think of electricity as what the voltage difference is between two things. For instance, there is a 120V difference between the red wire and the neutral white wire. There is 240V difference between the red and black.

A human body messing around with the wires is going to be close to the same voltage as "ground". If you're touching a piece of grounded metal, then you are at the same level as ground. The white neutral is also connected to ground (in most situations that a homeowner would run into in the US), so you can safely grab that wire and not get shocked.

So maybe you have the saying misinterpreted? The neutral does not have voltage (because it's bonded to ground), but any time something is plugged in, it is carrying current.